Consider:
sched_setaffinity(p, X); sched_setaffinity(p, Y);
Then the first will install p->migration_pending = &my_pending; and
issue stop_one_cpu_nowait(pending); and the second one will read
p->migration_pending and _also_ issue: stop_one_cpu_nowait(pending),
the _SAME_ @pending.
This causes stopper list corruption.
Add set_affinity_pending::stop_pending, to indicate if a stopper is in
progress.
Fixes: 6d337eab04 ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Cc: stable@kernel.org
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210224131355.649146419@infradead.org
idle load balance is the only user of update_nohz_stats and doesn't use
force parameter. Remove it
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210224133007.28644-4-vincent.guittot@linaro.org
When the purpose of migration_cpu_stop() is to migrate the task to
'any' valid CPU, don't migrate the task when it's already running on a
valid CPU.
Fixes: 6d337eab04 ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Cc: stable@kernel.org
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210224131355.569238629@infradead.org
The return of _nohz_idle_balance() is not used anymore so we can remove
it
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210224133007.28644-3-vincent.guittot@linaro.org
The SCA_MIGRATE_ENABLE and task_running() cases are almost identical,
collapse them to avoid further duplication.
Fixes: 6d337eab04 ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Cc: stable@kernel.org
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210224131355.500108964@infradead.org
newidle_balance runs with both preempt and irq disabled which prevent
local irq to run during this period. The duration for updating the
blocked load of CPUs varies according to the number of CPU cgroups
with non-decayed load and extends this critical period to an uncontrolled
level.
Remove the update from newidle_balance and trigger a normal ILB that
will take care of the update instead.
This reduces the IRQ latency from O(nr_cgroups * nr_nohz_cpus) to
O(nr_cgroups).
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210224133007.28644-2-vincent.guittot@linaro.org
Since, when ->stop_pending, only the stopper can uninstall
p->migration_pending. This could simplify a few ifs, because:
(pending != NULL) => (pending == p->migration_pending)
Also, the fatty comment above affine_move_task() probably needs a bit
of gardening.
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
When affine_move_task() issues a migration_cpu_stop(), the purpose of
that function is to complete that @pending, not any random other
p->migration_pending that might have gotten installed since.
This realization much simplifies migration_cpu_stop() and allows
further necessary steps to fix all this as it provides the guarantee
that @pending's stopper will complete @pending (and not some random
other @pending).
Fixes: 6d337eab04 ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Cc: stable@kernel.org
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210224131355.430014682@infradead.org
When affine_move_task(p) is called on a running task @p, which is not
otherwise already changing affinity, we'll first set
p->migration_pending and then do:
stop_one_cpu(cpu_of_rq(rq), migration_cpu_stop, &arg);
This then gets us to migration_cpu_stop() running on the CPU that was
previously running our victim task @p.
If we find that our task is no longer on that runqueue (this can
happen because of a concurrent migration due to load-balance etc.),
then we'll end up at the:
} else if (dest_cpu < 1 || pending) {
branch. Which we'll take because we set pending earlier. Here we first
check if the task @p has already satisfied the affinity constraints,
if so we bail early [A]. Otherwise we'll reissue migration_cpu_stop()
onto the CPU that is now hosting our task @p:
stop_one_cpu_nowait(cpu_of(rq), migration_cpu_stop,
&pending->arg, &pending->stop_work);
Except, we've never initialized pending->arg, which will be all 0s.
This then results in running migration_cpu_stop() on the next CPU with
arg->p == NULL, which gives the by now obvious result of fireworks.
The cure is to change affine_move_task() to always use pending->arg,
furthermore we can use the exact same pattern as the
SCA_MIGRATE_ENABLE case, since we'll block on the pending->done
completion anyway, no point in adding yet another completion in
stop_one_cpu().
This then gives a clear distinction between the two
migration_cpu_stop() use cases:
- sched_exec() / migrate_task_to() : arg->pending == NULL
- affine_move_task() : arg->pending != NULL;
And we can have it ignore p->migration_pending when !arg->pending. Any
stop work from sched_exec() / migrate_task_to() is in addition to stop
works from affine_move_task(), which will be sufficient to issue the
completion.
Fixes: 6d337eab04 ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Cc: stable@kernel.org
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210224131355.357743989@infradead.org
Drop repeated words in kernel/events/.
{if, the, that, with, time}
Drop repeated words in kernel/locking/.
{it, no, the}
Drop repeated words in kernel/sched/.
{in, not}
Link: https://lkml.kernel.org/r/20210127023412.26292-1-rdunlap@infradead.org
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Will Deacon <will@kernel.org> [kernel/locking/]
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Will Deacon <will@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
- Address cpufreq regression introduced in 5.11 that causes
CPU frequency reporting to be distorted on systems with CPPC
that use acpi-cpufreq as the scaling driver (Rafael Wysocki).
- Fix regression introduced during the 5.10 development cycle
related to CPU hotplug and policy recreation in the
qcom-cpufreq-hw driver (Shawn Guo).
- Fix recent regression in the operating performance points (OPP)
framework that may cause frequency updates to be skipped by
mistake in some cases (Jonathan Marek).
- Simplify schedutil governor code and remove a misleading comment
from it (Yue Hu).
- Fix kerneldoc comment typo in the cpufreq core (Yue Hu).
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Merge tag 'pm-5.12-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
Pull more power management updates from Rafael Wysocki:
"These are fixes and cleanups on top of the power management material
for 5.12-rc1 merged previously.
Specifics:
- Address cpufreq regression introduced in 5.11 that causes CPU
frequency reporting to be distorted on systems with CPPC that use
acpi-cpufreq as the scaling driver (Rafael Wysocki).
- Fix regression introduced during the 5.10 development cycle related
to CPU hotplug and policy recreation in the qcom-cpufreq-hw driver
(Shawn Guo).
- Fix recent regression in the operating performance points (OPP)
framework that may cause frequency updates to be skipped by mistake
in some cases (Jonathan Marek).
- Simplify schedutil governor code and remove a misleading comment
from it (Yue Hu).
- Fix kerneldoc comment typo in the cpufreq core (Yue Hu)"
* tag 'pm-5.12-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
cpufreq: Fix typo in kerneldoc comment
cpufreq: schedutil: Remove update_lock comment from struct sugov_policy definition
cpufreq: schedutil: Remove needless sg_policy parameter from ignore_dl_rate_limit()
cpufreq: ACPI: Set cpuinfo.max_freq directly if max boost is known
cpufreq: qcom-hw: drop devm_xxx() calls from init/exit hooks
opp: Don't skip freq update for different frequency
- Support for userspace to emulate Xen hypercalls
- Raise the maximum number of user memslots
- Scalability improvements for the new MMU. Instead of the complex
"fast page fault" logic that is used in mmu.c, tdp_mmu.c uses an
rwlock so that page faults are concurrent, but the code that can run
against page faults is limited. Right now only page faults take the
lock for reading; in the future this will be extended to some
cases of page table destruction. I hope to switch the default MMU
around 5.12-rc3 (some testing was delayed due to Chinese New Year).
- Cleanups for MAXPHYADDR checks
- Use static calls for vendor-specific callbacks
- On AMD, use VMLOAD/VMSAVE to save and restore host state
- Stop using deprecated jump label APIs
- Workaround for AMD erratum that made nested virtualization unreliable
- Support for LBR emulation in the guest
- Support for communicating bus lock vmexits to userspace
- Add support for SEV attestation command
- Miscellaneous cleanups
PPC:
- Support for second data watchpoint on POWER10
- Remove some complex workarounds for buggy early versions of POWER9
- Guest entry/exit fixes
ARM64
- Make the nVHE EL2 object relocatable
- Cleanups for concurrent translation faults hitting the same page
- Support for the standard TRNG hypervisor call
- A bunch of small PMU/Debug fixes
- Simplification of the early init hypercall handling
Non-KVM changes (with acks):
- Detection of contended rwlocks (implemented only for qrwlocks,
because KVM only needs it for x86)
- Allow __DISABLE_EXPORTS from assembly code
- Provide a saner follow_pfn replacements for modules
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
Pull KVM updates from Paolo Bonzini:
"x86:
- Support for userspace to emulate Xen hypercalls
- Raise the maximum number of user memslots
- Scalability improvements for the new MMU.
Instead of the complex "fast page fault" logic that is used in
mmu.c, tdp_mmu.c uses an rwlock so that page faults are concurrent,
but the code that can run against page faults is limited. Right now
only page faults take the lock for reading; in the future this will
be extended to some cases of page table destruction. I hope to
switch the default MMU around 5.12-rc3 (some testing was delayed
due to Chinese New Year).
- Cleanups for MAXPHYADDR checks
- Use static calls for vendor-specific callbacks
- On AMD, use VMLOAD/VMSAVE to save and restore host state
- Stop using deprecated jump label APIs
- Workaround for AMD erratum that made nested virtualization
unreliable
- Support for LBR emulation in the guest
- Support for communicating bus lock vmexits to userspace
- Add support for SEV attestation command
- Miscellaneous cleanups
PPC:
- Support for second data watchpoint on POWER10
- Remove some complex workarounds for buggy early versions of POWER9
- Guest entry/exit fixes
ARM64:
- Make the nVHE EL2 object relocatable
- Cleanups for concurrent translation faults hitting the same page
- Support for the standard TRNG hypervisor call
- A bunch of small PMU/Debug fixes
- Simplification of the early init hypercall handling
Non-KVM changes (with acks):
- Detection of contended rwlocks (implemented only for qrwlocks,
because KVM only needs it for x86)
- Allow __DISABLE_EXPORTS from assembly code
- Provide a saner follow_pfn replacements for modules"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (192 commits)
KVM: x86/xen: Explicitly pad struct compat_vcpu_info to 64 bytes
KVM: selftests: Don't bother mapping GVA for Xen shinfo test
KVM: selftests: Fix hex vs. decimal snafu in Xen test
KVM: selftests: Fix size of memslots created by Xen tests
KVM: selftests: Ignore recently added Xen tests' build output
KVM: selftests: Add missing header file needed by xAPIC IPI tests
KVM: selftests: Add operand to vmsave/vmload/vmrun in svm.c
KVM: SVM: Make symbol 'svm_gp_erratum_intercept' static
locking/arch: Move qrwlock.h include after qspinlock.h
KVM: PPC: Book3S HV: Fix host radix SLB optimisation with hash guests
KVM: PPC: Book3S HV: Ensure radix guest has no SLB entries
KVM: PPC: Don't always report hash MMU capability for P9 < DD2.2
KVM: PPC: Book3S HV: Save and restore FSCR in the P9 path
KVM: PPC: remove unneeded semicolon
KVM: PPC: Book3S HV: Use POWER9 SLBIA IH=6 variant to clear SLB
KVM: PPC: Book3S HV: No need to clear radix host SLB before loading HPT guest
KVM: PPC: Book3S HV: Fix radix guest SLB side channel
KVM: PPC: Book3S HV: Remove support for running HPT guest on RPT host without mixed mode support
KVM: PPC: Book3S HV: Introduce new capability for 2nd DAWR
KVM: PPC: Book3S HV: Add infrastructure to support 2nd DAWR
...
[ NOTE: unfortunately this tree had to be freshly rebased today,
it's a same-content tree of 82891be90f3c (-next published)
merged with v5.11.
The main reason for the rebase was an authorship misattribution
problem with a new commit, which we noticed in the last minute,
and which we didn't want to be merged upstream. The offending
commit was deep in the tree, and dependent commits had to be
rebased as well. ]
- Core scheduler updates:
- Add CONFIG_PREEMPT_DYNAMIC: this in its current form adds the
preempt=none/voluntary/full boot options (default: full),
to allow distros to build a PREEMPT kernel but fall back to
close to PREEMPT_VOLUNTARY (or PREEMPT_NONE) runtime scheduling
behavior via a boot time selection.
There's also the /debug/sched_debug switch to do this runtime.
This feature is implemented via runtime patching (a new variant of static calls).
The scope of the runtime patching can be best reviewed by looking
at the sched_dynamic_update() function in kernel/sched/core.c.
( Note that the dynamic none/voluntary mode isn't 100% identical,
for example preempt-RCU is available in all cases, plus the
preempt count is maintained in all models, which has runtime
overhead even with the code patching. )
The PREEMPT_VOLUNTARY/PREEMPT_NONE models, used by the vast majority
of distributions, are supposed to be unaffected.
- Fix ignored rescheduling after rcu_eqs_enter(). This is a bug that
was found via rcutorture triggering a hang. The bug is that
rcu_idle_enter() may wake up a NOCB kthread, but this happens after
the last generic need_resched() check. Some cpuidle drivers fix it
by chance but many others don't.
In true 2020 fashion the original bug fix has grown into a 5-patch
scheduler/RCU fix series plus another 16 RCU patches to address
the underlying issue of missed preemption events. These are the
initial fixes that should fix current incarnations of the bug.
- Clean up rbtree usage in the scheduler, by providing & using the following
consistent set of rbtree APIs:
partial-order; less() based:
- rb_add(): add a new entry to the rbtree
- rb_add_cached(): like rb_add(), but for a rb_root_cached
total-order; cmp() based:
- rb_find(): find an entry in an rbtree
- rb_find_add(): find an entry, and add if not found
- rb_find_first(): find the first (leftmost) matching entry
- rb_next_match(): continue from rb_find_first()
- rb_for_each(): iterate a sub-tree using the previous two
- Improve the SMP/NUMA load-balancer: scan for an idle sibling in a single pass.
This is a 4-commit series where each commit improves one aspect of the idle
sibling scan logic.
- Improve the cpufreq cooling driver by getting the effective CPU utilization
metrics from the scheduler
- Improve the fair scheduler's active load-balancing logic by reducing the number
of active LB attempts & lengthen the load-balancing interval. This improves
stress-ng mmapfork performance.
- Fix CFS's estimated utilization (util_est) calculation bug that can result in
too high utilization values
- Misc updates & fixes:
- Fix the HRTICK reprogramming & optimization feature
- Fix SCHED_SOFTIRQ raising race & warning in the CPU offlining code
- Reduce dl_add_task_root_domain() overhead
- Fix uprobes refcount bug
- Process pending softirqs in flush_smp_call_function_from_idle()
- Clean up task priority related defines, remove *USER_*PRIO and
USER_PRIO()
- Simplify the sched_init_numa() deduplication sort
- Documentation updates
- Fix EAS bug in update_misfit_status(), which degraded the quality
of energy-balancing
- Smaller cleanups
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-core-2021-02-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
"Core scheduler updates:
- Add CONFIG_PREEMPT_DYNAMIC: this in its current form adds the
preempt=none/voluntary/full boot options (default: full), to allow
distros to build a PREEMPT kernel but fall back to close to
PREEMPT_VOLUNTARY (or PREEMPT_NONE) runtime scheduling behavior via
a boot time selection.
There's also the /debug/sched_debug switch to do this runtime.
This feature is implemented via runtime patching (a new variant of
static calls).
The scope of the runtime patching can be best reviewed by looking
at the sched_dynamic_update() function in kernel/sched/core.c.
( Note that the dynamic none/voluntary mode isn't 100% identical,
for example preempt-RCU is available in all cases, plus the
preempt count is maintained in all models, which has runtime
overhead even with the code patching. )
The PREEMPT_VOLUNTARY/PREEMPT_NONE models, used by the vast
majority of distributions, are supposed to be unaffected.
- Fix ignored rescheduling after rcu_eqs_enter(). This is a bug that
was found via rcutorture triggering a hang. The bug is that
rcu_idle_enter() may wake up a NOCB kthread, but this happens after
the last generic need_resched() check. Some cpuidle drivers fix it
by chance but many others don't.
In true 2020 fashion the original bug fix has grown into a 5-patch
scheduler/RCU fix series plus another 16 RCU patches to address the
underlying issue of missed preemption events. These are the initial
fixes that should fix current incarnations of the bug.
- Clean up rbtree usage in the scheduler, by providing & using the
following consistent set of rbtree APIs:
partial-order; less() based:
- rb_add(): add a new entry to the rbtree
- rb_add_cached(): like rb_add(), but for a rb_root_cached
total-order; cmp() based:
- rb_find(): find an entry in an rbtree
- rb_find_add(): find an entry, and add if not found
- rb_find_first(): find the first (leftmost) matching entry
- rb_next_match(): continue from rb_find_first()
- rb_for_each(): iterate a sub-tree using the previous two
- Improve the SMP/NUMA load-balancer: scan for an idle sibling in a
single pass. This is a 4-commit series where each commit improves
one aspect of the idle sibling scan logic.
- Improve the cpufreq cooling driver by getting the effective CPU
utilization metrics from the scheduler
- Improve the fair scheduler's active load-balancing logic by
reducing the number of active LB attempts & lengthen the
load-balancing interval. This improves stress-ng mmapfork
performance.
- Fix CFS's estimated utilization (util_est) calculation bug that can
result in too high utilization values
Misc updates & fixes:
- Fix the HRTICK reprogramming & optimization feature
- Fix SCHED_SOFTIRQ raising race & warning in the CPU offlining code
- Reduce dl_add_task_root_domain() overhead
- Fix uprobes refcount bug
- Process pending softirqs in flush_smp_call_function_from_idle()
- Clean up task priority related defines, remove *USER_*PRIO and
USER_PRIO()
- Simplify the sched_init_numa() deduplication sort
- Documentation updates
- Fix EAS bug in update_misfit_status(), which degraded the quality
of energy-balancing
- Smaller cleanups"
* tag 'sched-core-2021-02-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (51 commits)
sched,x86: Allow !PREEMPT_DYNAMIC
entry/kvm: Explicitly flush pending rcuog wakeup before last rescheduling point
entry: Explicitly flush pending rcuog wakeup before last rescheduling point
rcu/nocb: Trigger self-IPI on late deferred wake up before user resume
rcu/nocb: Perform deferred wake up before last idle's need_resched() check
rcu: Pull deferred rcuog wake up to rcu_eqs_enter() callers
sched/features: Distinguish between NORMAL and DEADLINE hrtick
sched/features: Fix hrtick reprogramming
sched/deadline: Reduce rq lock contention in dl_add_task_root_domain()
uprobes: (Re)add missing get_uprobe() in __find_uprobe()
smp: Process pending softirqs in flush_smp_call_function_from_idle()
sched: Harden PREEMPT_DYNAMIC
static_call: Allow module use without exposing static_call_key
sched: Add /debug/sched_preempt
preempt/dynamic: Support dynamic preempt with preempt= boot option
preempt/dynamic: Provide irqentry_exit_cond_resched() static call
preempt/dynamic: Provide preempt_schedule[_notrace]() static calls
preempt/dynamic: Provide cond_resched() and might_resched() static calls
preempt: Introduce CONFIG_PREEMPT_DYNAMIC
static_call: Provide DEFINE_STATIC_CALL_RET0()
...
Currently, update_lock is also used in sugov_update_single_freq().
The comment is not helpful anymore.
Signed-off-by: Yue Hu <huyue2@yulong.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
[ rjw: Subject edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Since sg_policy is a member of struct sugov_cpu.
Also remove the local variable in sugov_update_single_common() to
make the code more clean.
Signed-off-by: Yue Hu <huyue2@yulong.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
[ rjw: Minor subject edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Entering RCU idle mode may cause a deferred wake up of an RCU NOCB_GP
kthread (rcuog) to be serviced.
Usually a local wake up happening while running the idle task is handled
in one of the need_resched() checks carefully placed within the idle
loop that can break to the scheduler.
Unfortunately the call to rcu_idle_enter() is already beyond the last
generic need_resched() check and we may halt the CPU with a resched
request unhandled, leaving the task hanging.
Fix this with splitting the rcuog wakeup handling from rcu_idle_enter()
and place it before the last generic need_resched() check in the idle
loop. It is then assumed that no call to call_rcu() will be performed
after that in the idle loop until the CPU is put in low power mode.
Fixes: 96d3fd0d31 (rcu: Break call_rcu() deadlock involving scheduler and perf)
Reported-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20210131230548.32970-3-frederic@kernel.org
The HRTICK feature has traditionally been servicing configurations that
need precise preemptions point for NORMAL tasks. More recently, the
feature has been extended to also service DEADLINE tasks with stringent
runtime enforcement needs (e.g., runtime < 1ms with HZ=1000).
Enabling HRTICK sched feature currently enables the additional timer and
task tick for both classes, which might introduced undesired overhead
for no additional benefit if one needed it only for one of the cases.
Separate HRTICK sched feature in two (and leave the traditional case
name unmodified) so that it can be selectively enabled when needed.
With:
$ echo HRTICK > /sys/kernel/debug/sched_features
the NORMAL/fair hrtick gets enabled.
With:
$ echo HRTICK_DL > /sys/kernel/debug/sched_features
the DEADLINE hrtick gets enabled.
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20210208073554.14629-3-juri.lelli@redhat.com
Hung tasks and RCU stall cases were reported on systems which were not
100% busy. Investigation of such unexpected cases (no sign of potential
starvation caused by tasks hogging the system) pointed out that the
periodic sched tick timer wasn't serviced anymore after a certain point
and that caused all machinery that depends on it (timers, RCU, etc.) to
stop working as well. This issues was however only reproducible if
HRTICK was enabled.
Looking at core dumps it was found that the rbtree of the hrtimer base
used also for the hrtick was corrupted (i.e. next as seen from the base
root and actual leftmost obtained by traversing the tree are different).
Same base is also used for periodic tick hrtimer, which might get "lost"
if the rbtree gets corrupted.
Much alike what described in commit 1f71addd34 ("tick/sched: Do not
mess with an enqueued hrtimer") there is a race window between
hrtimer_set_expires() in hrtick_start and hrtimer_start_expires() in
__hrtick_restart() in which the former might be operating on an already
queued hrtick hrtimer, which might lead to corruption of the base.
Use hrtick_start() (which removes the timer before enqueuing it back) to
ensure hrtick hrtimer reprogramming is entirely guarded by the base
lock, so that no race conditions can occur.
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20210208073554.14629-2-juri.lelli@redhat.com
dl_add_task_root_domain() is called during sched domain rebuild:
rebuild_sched_domains_locked()
partition_and_rebuild_sched_domains()
rebuild_root_domains()
for all top_cpuset descendants:
update_tasks_root_domain()
for all tasks of cpuset:
dl_add_task_root_domain()
Change it so that only the task pi lock is taken to check if the task
has a SCHED_DEADLINE (DL) policy. In case that p is a DL task take the
rq lock as well to be able to safely de-reference root domain's DL
bandwidth structure.
Most of the tasks will have another policy (namely SCHED_NORMAL) and
can now bail without taking the rq lock.
One thing to note here: Even in case that there aren't any DL user
tasks, a slow frequency switching system with cpufreq gov schedutil has
a DL task (sugov) per frequency domain running which participates in DL
bandwidth management.
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Quentin Perret <qperret@google.com>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Acked-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lkml.kernel.org/r/20210119083542.19856-1-dietmar.eggemann@arm.com
Use the new EXPORT_STATIC_CALL_TRAMP() / static_call_mod() to unexport
the static_call_key for the PREEMPT_DYNAMIC calls such that modules
can no longer update these calls.
Having modules change/hi-jack the preemption calls would be horrible.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Provide static calls to control preempt_schedule[_notrace]()
(called in CONFIG_PREEMPT) so that we can override their behaviour when
preempt= is overriden.
Since the default behaviour is full preemption, both their calls are
initialized to the arch provided wrapper, if any.
[fweisbec: only define static calls when PREEMPT_DYNAMIC, make it less
dependent on x86 with __preempt_schedule_func]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20210118141223.123667-7-frederic@kernel.org
Provide static calls to control cond_resched() (called in !CONFIG_PREEMPT)
and might_resched() (called in CONFIG_PREEMPT_VOLUNTARY) to that we
can override their behaviour when preempt= is overriden.
Since the default behaviour is full preemption, both their calls are
ignored when preempt= isn't passed.
[fweisbec: branch might_resched() directly to __cond_resched(), only
define static calls when PREEMPT_DYNAMIC]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20210118141223.123667-6-frederic@kernel.org
The description of the RT offset and the values for 'normal' tasks needs
update. Moreover there are DL tasks now.
task_prio() has to stay like it is to guarantee compatibility with the
/proc/<pid>/stat priority field:
# cat /proc/<pid>/stat | awk '{ print $18; }'
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20210128131040.296856-4-dietmar.eggemann@arm.com
The only remaining use of MAX_USER_PRIO (and USER_PRIO) is the
SCALE_PRIO() definition in the PowerPC Cell architecture's Synergistic
Processor Unit (SPU) scheduler. TASK_USER_PRIO isn't used anymore.
Commit fe443ef2ac ("[POWERPC] spusched: Dynamic timeslicing for
SCHED_OTHER") copied SCALE_PRIO() from the task scheduler in v2.6.23.
Commit a4ec24b48d ("sched: tidy up SCHED_RR") removed it from the task
scheduler in v2.6.24.
Commit 3ee237dddc ("sched/prio: Add 3 macros of MAX_NICE, MIN_NICE and
NICE_WIDTH in prio.h") introduced NICE_WIDTH much later.
With:
MAX_USER_PRIO = USER_PRIO(MAX_PRIO)
= MAX_PRIO - MAX_RT_PRIO
MAX_PRIO = MAX_RT_PRIO + NICE_WIDTH
MAX_USER_PRIO = MAX_RT_PRIO + NICE_WIDTH - MAX_RT_PRIO
MAX_USER_PRIO = NICE_WIDTH
MAX_USER_PRIO can be replaced by NICE_WIDTH to be able to remove all the
{*_}USER_PRIO defines.
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20210128131040.296856-3-dietmar.eggemann@arm.com
Commit d46523ea32 ("[PATCH] fix MAX_USER_RT_PRIO and MAX_RT_PRIO")
was introduced due to a a small time period in which the realtime patch
set was using different values for MAX_USER_RT_PRIO and MAX_RT_PRIO.
This is no longer true, i.e. now MAX_RT_PRIO == MAX_USER_RT_PRIO.
Get rid of MAX_USER_RT_PRIO and make everything use MAX_RT_PRIO
instead.
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20210128131040.296856-2-dietmar.eggemann@arm.com
Commit "sched/topology: Make sched_init_numa() use a set for the
deduplicating sort" allocates 'i + nr_levels (level)' instead of
'i + nr_levels + 1' sched_domain_topology_level.
This led to an Oops (on Arm64 juno with CONFIG_SCHED_DEBUG):
sched_init_domains
build_sched_domains()
__free_domain_allocs()
__sdt_free() {
...
for_each_sd_topology(tl)
...
sd = *per_cpu_ptr(sdd->sd, j); <--
...
}
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Vincent Guittot <vincent.guittot@linaro.org>
Tested-by: Barry Song <song.bao.hua@hisilicon.com>
Link: https://lkml.kernel.org/r/6000e39e-7d28-c360-9cd6-8798fd22a9bf@arm.com
Reduce rbtree boiler plate by using the new helpers.
Make rb_add_cached() / rb_erase_cached() return a pointer to the
leftmost node to aid in updating additional state.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Reduce rbtree boiler plate by using the new helper function.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Both select_idle_core() and select_idle_cpu() do a loop over the same
cpumask. Observe that by clearing the already visited CPUs, we can
fold the iteration and iterate a core at a time.
All we need to do is remember any non-idle CPU we encountered while
scanning for an idle core. This way we'll only iterate every CPU once.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210127135203.19633-5-mgorman@techsingularity.net
In order to make the next patch more readable, and to quantify the
actual effectiveness of this pass, start by removing it.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210125085909.4600-4-mgorman@techsingularity.net
Pull RCU updates from Paul E. McKenney:
- Documentation updates.
- Miscellaneous fixes.
- kfree_rcu() updates: Addition of mem_dump_obj() to provide allocator return
addresses to more easily locate bugs. This has a couple of RCU-related commits,
but is mostly MM. Was pulled in with akpm's agreement.
- Per-callback-batch tracking of numbers of callbacks,
which enables better debugging information and smarter
reactions to large numbers of callbacks.
- The first round of changes to allow CPUs to be runtime switched from and to
callback-offloaded state.
- CONFIG_PREEMPT_RT-related changes.
- RCU CPU stall warning updates.
- Addition of polling grace-period APIs for SRCU.
- Torture-test and torture-test scripting updates, including a "torture everything"
script that runs rcutorture, locktorture, scftorture, rcuscale, and refscale.
Plus does an allmodconfig build.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Safely rescheduling while holding a spin lock is essential for keeping
long running kernel operations running smoothly. Add the facility to
cond_resched rwlocks.
CC: Ingo Molnar <mingo@redhat.com>
CC: Will Deacon <will@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Waiman Long <longman@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210202185734.1680553-9-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
As noted by Vincent Guittot, avg_scan_costs are calculated for SIS_PROP
even if SIS_PROP is disabled. Move the time calculations under a SIS_PROP
check and while we are at it, exclude the cost of initialising the CPU
mask from the average scan cost.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210125085909.4600-3-mgorman@techsingularity.net
SIS_AVG_CPU was introduced as a means of avoiding a search when the
average search cost indicated that the search would likely fail. It was
a blunt instrument and disabled by commit 4c77b18cf8 ("sched/fair: Make
select_idle_cpu() more aggressive") and later replaced with a proportional
search depth by commit 1ad3aaf3fc ("sched/core: Implement new approach
to scale select_idle_cpu()").
While there are corner cases where SIS_AVG_CPU is better, it has now been
disabled for almost three years. As the intent of SIS_PROP is to reduce
the time complexity of select_idle_cpu(), lets drop SIS_AVG_CPU and focus
on SIS_PROP as a throttling mechanism.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210125085909.4600-2-mgorman@techsingularity.net
The deduplicating sort in sched_init_numa() assumes that the first line in
the distance table contains all unique values in the entire table. I've
been trying to pen what this exactly means for the topology, but it's not
straightforward. For instance, topology.c uses this example:
node 0 1 2 3
0: 10 20 20 30
1: 20 10 20 20
2: 20 20 10 20
3: 30 20 20 10
0 ----- 1
| / |
| / |
| / |
2 ----- 3
Which works out just fine. However, if we swap nodes 0 and 1:
1 ----- 0
| / |
| / |
| / |
2 ----- 3
we get this distance table:
node 0 1 2 3
0: 10 20 20 20
1: 20 10 20 30
2: 20 20 10 20
3: 20 30 20 10
Which breaks the deduplicating sort (non-representative first line). In
this case this would just be a renumbering exercise, but it so happens that
we can have a deduplicating sort that goes through the whole table in O(n²)
at the extra cost of a temporary memory allocation (i.e. any form of set).
The ACPI spec (SLIT) mentions distances are encoded on 8 bits. Following
this, implement the set as a 256-bits bitmap. Should this not be
satisfactory (i.e. we want to support 32-bit values), then we'll have to go
for some other sparse set implementation.
This has the added benefit of letting us allocate just the right amount of
memory for sched_domains_numa_distance[], rather than an arbitrary
(nr_node_ids + 1).
Note: DT binding equivalent (distance-map) decodes distances as 32-bit
values.
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210122123943.1217-2-valentin.schneider@arm.com
If the task is pinned to a cpu, setting the misfit status means that
we'll unnecessarily continuously attempt to migrate the task but fail.
This continuous failure will cause the balance_interval to increase to
a high value, and eventually cause unnecessary significant delays in
balancing the system when real imbalance happens.
Caught while testing uclamp where rt-app calibration loop was pinned to
cpu 0, shortly after which we spawn another task with high util_clamp
value. The task was failing to migrate after over 40ms of runtime due to
balance_interval unnecessary expanded to a very high value from the
calibration loop.
Not done here, but it could be useful to extend the check for pinning to
verify that the affinity of the task has a cpu that fits. We could end
up in a similar situation otherwise.
Fixes: 3b1baa6496 ("sched/fair: Add 'group_misfit_task' load-balance type")
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Quentin Perret <qperret@google.com>
Acked-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210119120755.2425264-1-qais.yousef@arm.com
Now that we have KTHREAD_IS_PER_CPU to denote the critical per-cpu
tasks to retain during CPU offline, we can relax the warning in
set_cpus_allowed_ptr(). Any spurious kthread that wants to get on at
the last minute will get pushed off before it can run.
While during CPU online there is no harm, and actual benefit, to
allowing kthreads back on early, it simplifies hotplug code and fixes
a number of outstanding races.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Lai jiangshan <jiangshanlai@gmail.com>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Tested-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210121103507.240724591@infradead.org
Prior to commit 1cf12e08bc ("sched/hotplug: Consolidate task
migration on CPU unplug") we'd leave any task on the dying CPU and
break affinity and force them off at the very end.
This scheme had to change in order to enable migrate_disable(). One
cannot wait for migrate_disable() to complete while stuck in
stop_machine(). Furthermore, since we need at the very least: idle,
hotplug and stop threads at any point before stop_machine, we can't
break affinity and/or push those away.
Under the assumption that all per-cpu kthreads are sanely handled by
CPU hotplug, the new code no long breaks affinity or migrates any of
them (which then includes the critical ones above).
However, there's an important difference between per-cpu kthreads and
kthreads that happen to have a single CPU affinity which is lost. The
latter class very much relies on the forced affinity breaking and
migration semantics previously provided.
Use the new kthread_is_per_cpu() infrastructure to tighten
is_per_cpu_kthread() and fix the hot-unplug problems stemming from the
change.
Fixes: 1cf12e08bc ("sched/hotplug: Consolidate task migration on CPU unplug")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Tested-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210121103507.102416009@infradead.org
In preparation of using the balance_push state in ttwu() we need it to
provide a reliable and consistent state.
The immediate problem is that rq->balance_callback gets cleared every
schedule() and then re-set in the balance_push_callback() itself. This
is not a reliable signal, so add a variable that stays set during the
entire time.
Also move setting it before the synchronize_rcu() in
sched_cpu_deactivate(), such that we get guaranteed visibility to
ttwu(), which is a preempt-disable region.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Tested-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210121103506.966069627@infradead.org
We don't need to push away tasks when we come online, mark the push
complete right before the CPU dies.
XXX hotplug state machine has trouble with rollback here.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Tested-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210121103506.415606087@infradead.org
Since commit
1cf12e08bc ("sched/hotplug: Consolidate task migration on CPU unplug")
tasks are expected to move themselves out of a out-going CPU. For most
tasks this will be done automagically via BALANCE_PUSH, but percpu kthreads
will have to cooperate and move themselves away one way or another.
Currently, some percpu kthreads (workqueues being a notable exemple) do not
cooperate nicely and can end up on an out-going CPU at the time
sched_cpu_dying() is invoked.
Print the dying rq's tasks to shed some light on the stragglers.
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Tested-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210113183141.11974-1-valentin.schneider@arm.com
Use the task_current() function where appropriate.
No functional change.
Signed-off-by: Hui Su <sh_def@163.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Link: https://lkml.kernel.org/r/20201030173223.GA52339@rlk
Active balance is triggered for a number of voluntary cases like misfit
or pinned tasks cases but also after that a number of load balance
attempts failed to migrate a task. There is no need to use active load
balance when the group is overloaded because an overloaded state means
that there is at least one waiting task. Nevertheless, the waiting task
is not selected and detached until the threshold becomes higher than its
load. This threshold increases with the number of failed lb (see the
condition if ((load >> env->sd->nr_balance_failed) > env->imbalance) in
detach_tasks()) and the waiting task will end up to be selected after a
number of attempts.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lkml.kernel.org/r/20210107103325.30851-4-vincent.guittot@linaro.org
Setting LBF_ALL_PINNED during active load balance is only valid when there
is only 1 running task on the rq otherwise this ends up increasing the
balance interval whereas other tasks could migrate after the next interval
once they become cache-cold as an example.
LBF_ALL_PINNED flag is now always set it by default. It is then cleared
when we find one task that can be pulled when calling detach_tasks() or
during active migration.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lkml.kernel.org/r/20210107103325.30851-3-vincent.guittot@linaro.org
Don't waste time checking whether an idle cfs_rq could be the busiest
queue. Furthermore, this can end up selecting a cfs_rq with a high load
but being idle in case of migrate_load.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lkml.kernel.org/r/20210107103325.30851-2-vincent.guittot@linaro.org
CPU (root cfs_rq) estimated utilization (util_est) is currently used in
dequeue_task_fair() to drive frequency selection before it is updated.
with:
CPU_util : rq->cfs.avg.util_avg
CPU_util_est : rq->cfs.avg.util_est
CPU_utilization : max(CPU_util, CPU_util_est)
task_util : p->se.avg.util_avg
task_util_est : p->se.avg.util_est
dequeue_task_fair():
/* (1) CPU_util and task_util update + inform schedutil about
CPU_utilization changes */
for_each_sched_entity() /* 2 loops */
(dequeue_entity() ->) update_load_avg() -> cfs_rq_util_change()
-> cpufreq_update_util() ->...-> sugov_update_[shared\|single]
-> sugov_get_util() -> cpu_util_cfs()
/* (2) CPU_util_est and task_util_est update */
util_est_dequeue()
cpu_util_cfs() uses CPU_utilization which could lead to a false (too
high) utilization value for schedutil in task ramp-down or ramp-up
scenarios during task dequeue.
To mitigate the issue split the util_est update (2) into:
(A) CPU_util_est update in util_est_dequeue()
(B) task_util_est update in util_est_update()
Place (A) before (1) and keep (B) where (2) is. The latter is necessary
since (B) relies on task_util update in (1).
Fixes: 7f65ea42eb ("sched/fair: Add util_est on top of PELT")
Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/1608283672-18240-1-git-send-email-xuewen.yan94@gmail.com
SCHED_SOFTIRQ is raised to trigger periodic load balancing. When CPU is not
active, CPU should not participate in load balancing.
The scheduler uses nohz.idle_cpus_mask to keep track of the CPUs which can
do idle load balancing. When bringing a CPU up the CPU is added to the mask
when it reaches the active state, but on teardown the CPU stays in the mask
until it goes offline and invokes sched_cpu_dying().
When SCHED_SOFTIRQ is raised on a !active CPU, there might be a pending
softirq when stopping the tick which triggers a warning in NOHZ code. The
SCHED_SOFTIRQ can also be raised by the scheduler tick which has the same
issue.
Therefore remove the CPU from nohz.idle_cpus_mask when it is marked
inactive and also prevent the scheduler_tick() from raising SCHED_SOFTIRQ
after this point.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Link: https://lkml.kernel.org/r/20201215104400.9435-1-anna-maria@linutronix.de
There is nothing schedutil specific in schedutil_cpu_util(), rename it
to effective_cpu_util(). Also create and expose another wrapper
sched_cpu_util() which can be used by other parts of the kernel, like
thermal core (that will be done in a later commit).
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lkml.kernel.org/r/db011961fb3bb8bef1c0eda5cd64564637d3ef31.1607400596.git.viresh.kumar@linaro.org
- Rework the passive-mode "fast switch" path in the intel_pstate
driver to allow it receive the minimum (required) and target
(desired) performance information from the schedutil governor so
as to avoid running some workloads too fast (Rafael Wysocki).
- Make the intel_pstate driver allow the policy max limit to be
increased after the guaranteed performance value for the given
CPU has increased (Rafael Wysocki).
- Clean up the handling of CPU coordination types in the CPPC
cpufreq driver and make it export frequency domains information
to user space via sysfs (Ionela Voinescu).
- Fix the ACPI code handling processor objects to use a correct
coordination type when it fails to map frequency domains and drop
a redundant CPU map initialization from it (Ionela Voinescu, Punit
Agrawal).
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Merge tag 'pm-5.11-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
Pull more power management updates from Rafael Wysocki:
"These update the CPPC cpufreq driver and intel_pstate (which involves
updating the cpufreq core and the schedutil governor) and make
janitorial changes in the ACPI code handling processor objects.
Specifics:
- Rework the passive-mode "fast switch" path in the intel_pstate
driver to allow it receive the minimum (required) and target
(desired) performance information from the schedutil governor so as
to avoid running some workloads too fast (Rafael Wysocki).
- Make the intel_pstate driver allow the policy max limit to be
increased after the guaranteed performance value for the given CPU
has increased (Rafael Wysocki).
- Clean up the handling of CPU coordination types in the CPPC cpufreq
driver and make it export frequency domains information to user
space via sysfs (Ionela Voinescu).
- Fix the ACPI code handling processor objects to use a correct
coordination type when it fails to map frequency domains and drop a
redundant CPU map initialization from it (Ionela Voinescu, Punit
Agrawal)"
* tag 'pm-5.11-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
cpufreq: intel_pstate: Use most recent guaranteed performance values
cpufreq: intel_pstate: Implement the ->adjust_perf() callback
cpufreq: Add special-purpose fast-switching callback for drivers
cpufreq: schedutil: Add util to struct sg_cpu
cppc_cpufreq: replace per-cpu data array with a list
cppc_cpufreq: expose information on frequency domains
cppc_cpufreq: clarify support for coordination types
cppc_cpufreq: use policy->cpu as driver of frequency setting
ACPI: processor: fix NONE coordination for domain mapping failure
* pm-cpufreq:
cpufreq: intel_pstate: Use most recent guaranteed performance values
cpufreq: intel_pstate: Implement the ->adjust_perf() callback
cpufreq: Add special-purpose fast-switching callback for drivers
cpufreq: schedutil: Add util to struct sg_cpu
cppc_cpufreq: replace per-cpu data array with a list
cppc_cpufreq: expose information on frequency domains
cppc_cpufreq: clarify support for coordination types
cppc_cpufreq: use policy->cpu as driver of frequency setting
ACPI: processor: fix NONE coordination for domain mapping failure
ACPI: processor: Drop duplicate setting of shared_cpu_map
* PSCI relay at EL2 when "protected KVM" is enabled
* New exception injection code
* Simplification of AArch32 system register handling
* Fix PMU accesses when no PMU is enabled
* Expose CSV3 on non-Meltdown hosts
* Cache hierarchy discovery fixes
* PV steal-time cleanups
* Allow function pointers at EL2
* Various host EL2 entry cleanups
* Simplification of the EL2 vector allocation
s390:
* memcg accouting for s390 specific parts of kvm and gmap
* selftest for diag318
* new kvm_stat for when async_pf falls back to sync
x86:
* Tracepoints for the new pagetable code from 5.10
* Catch VFIO and KVM irqfd events before userspace
* Reporting dirty pages to userspace with a ring buffer
* SEV-ES host support
* Nested VMX support for wait-for-SIPI activity state
* New feature flag (AVX512 FP16)
* New system ioctl to report Hyper-V-compatible paravirtualization features
Generic:
* Selftest improvements
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
Pull KVM updates from Paolo Bonzini:
"Much x86 work was pushed out to 5.12, but ARM more than made up for it.
ARM:
- PSCI relay at EL2 when "protected KVM" is enabled
- New exception injection code
- Simplification of AArch32 system register handling
- Fix PMU accesses when no PMU is enabled
- Expose CSV3 on non-Meltdown hosts
- Cache hierarchy discovery fixes
- PV steal-time cleanups
- Allow function pointers at EL2
- Various host EL2 entry cleanups
- Simplification of the EL2 vector allocation
s390:
- memcg accouting for s390 specific parts of kvm and gmap
- selftest for diag318
- new kvm_stat for when async_pf falls back to sync
x86:
- Tracepoints for the new pagetable code from 5.10
- Catch VFIO and KVM irqfd events before userspace
- Reporting dirty pages to userspace with a ring buffer
- SEV-ES host support
- Nested VMX support for wait-for-SIPI activity state
- New feature flag (AVX512 FP16)
- New system ioctl to report Hyper-V-compatible paravirtualization features
Generic:
- Selftest improvements"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (171 commits)
KVM: SVM: fix 32-bit compilation
KVM: SVM: Add AP_JUMP_TABLE support in prep for AP booting
KVM: SVM: Provide support to launch and run an SEV-ES guest
KVM: SVM: Provide an updated VMRUN invocation for SEV-ES guests
KVM: SVM: Provide support for SEV-ES vCPU loading
KVM: SVM: Provide support for SEV-ES vCPU creation/loading
KVM: SVM: Update ASID allocation to support SEV-ES guests
KVM: SVM: Set the encryption mask for the SVM host save area
KVM: SVM: Add NMI support for an SEV-ES guest
KVM: SVM: Guest FPU state save/restore not needed for SEV-ES guest
KVM: SVM: Do not report support for SMM for an SEV-ES guest
KVM: x86: Update __get_sregs() / __set_sregs() to support SEV-ES
KVM: SVM: Add support for CR8 write traps for an SEV-ES guest
KVM: SVM: Add support for CR4 write traps for an SEV-ES guest
KVM: SVM: Add support for CR0 write traps for an SEV-ES guest
KVM: SVM: Add support for EFER write traps for an SEV-ES guest
KVM: SVM: Support string IO operations for an SEV-ES guest
KVM: SVM: Support MMIO for an SEV-ES guest
KVM: SVM: Create trace events for VMGEXIT MSR protocol processing
KVM: SVM: Create trace events for VMGEXIT processing
...
- Use local_clock() instead of jiffies in the cpufreq statistics to
improve accuracy (Viresh Kumar).
- Fix up OPP usage in the cpufreq-dt and qcom-cpufreq-nvmem cpufreq
drivers (Viresh Kumar).
- Clean up the cpufreq core, the intel_pstate driver and the
schedutil cpufreq governor (Rafael Wysocki).
- Fix up error code paths in the sti-cpufreq and mediatek cpufreq
drivers (Yangtao Li, Qinglang Miao).
- Fix cpufreq_online() to return error codes instead of success (0)
in all cases when it fails (Wang ShaoBo).
- Add mt8167 support to the mediatek cpufreq driver and blacklist
mt8516 in the cpufreq-dt-platdev driver (Fabien Parent).
- Modify the tegra194 cpufreq driver to always return values from
the frequency table as the current frequency and clean up that
driver (Sumit Gupta, Jon Hunter).
- Modify the arm_scmi cpufreq driver to allow it to discover the
power scale present in the performance protocol and provide this
information to the Energy Model (Lukasz Luba).
- Add missing MODULE_DEVICE_TABLE to several cpufreq drivers (Pali
Rohár).
- Clean up the CPPC cpufreq driver (Ionela Voinescu).
- Fix NVMEM_IMX_OCOTP dependency in the imx cpufreq driver (Arnd
Bergmann).
- Rework the poling interval selection for the polling state in
cpuidle (Mel Gorman).
- Enable suspend-to-idle for PSCI OSI mode in the PSCI cpuidle
driver (Ulf Hansson).
- Modify the OPP framework to support empty (node-less) OPP tables
in DT for passing dependency information (Nicola Mazzucato).
- Fix potential lockdep issue in the OPP core and clean up the OPP
core (Viresh Kumar).
- Modify dev_pm_opp_put_regulators() to accept a NULL argument and
update its users accordingly (Viresh Kumar).
- Add frequency changes tracepoint to devfreq (Matthias Kaehlcke).
- Add support for governor feature flags to devfreq, make devfreq
sysfs file permissions depend on the governor and clean up the
devfreq core (Chanwoo Choi).
- Clean up the tegra20 devfreq driver and deprecate it to allow
another driver based on EMC_STAT to be used instead of it (Dmitry
Osipenko).
- Add interconnect support to the tegra30 devfreq driver, allow it
to take the interconnect and OPP information from DT and clean it
up ((Dmitry Osipenko).
- Add interconnect support to the exynos-bus devfreq driver along
with interconnect properties documentation (Sylwester Nawrocki).
- Add suport for AMD Fam17h and Fam19h processors to the RAPL power
capping driver (Victor Ding, Kim Phillips).
- Fix handling of overly long constraint names in the powercap
framework (Lukasz Luba).
- Fix the wakeup configuration handling for bridges in the ACPI
device power management core (Rafael Wysocki).
- Add support for using an abstract scale for power units in the
Energy Model (EM) and document it (Lukasz Luba).
- Add em_cpu_energy() micro-optimization to the EM (Pavankumar
Kondeti).
- Modify the generic power domains (genpd) framwework to support
suspend-to-idle (Ulf Hansson).
- Fix creation of debugfs nodes in genpd (Thierry Strudel).
- Clean up genpd (Lina Iyer).
- Clean up the core system-wide suspend code and make it print
driver flags for devices with debug enabled (Alex Shi, Patrice
Chotard, Chen Yu).
- Modify the ACPI system reboot code to make it prepare for system
power off to avoid confusing the platform firmware (Kai-Heng Feng).
- Update the pm-graph (multiple changes, mostly usability-related)
and cpupower (online and offline CPU information support) PM
utilities (Todd Brandt, Brahadambal Srinivasan).
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Merge tag 'pm-5.11-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
Pull power management updates from Rafael Wysocki:
"These update cpufreq (core and drivers), cpuidle (polling state
implementation and the PSCI driver), the OPP (operating performance
points) framework, devfreq (core and drivers), the power capping RAPL
(Running Average Power Limit) driver, the Energy Model support, the
generic power domains (genpd) framework, the ACPI device power
management, the core system-wide suspend code and power management
utilities.
Specifics:
- Use local_clock() instead of jiffies in the cpufreq statistics to
improve accuracy (Viresh Kumar).
- Fix up OPP usage in the cpufreq-dt and qcom-cpufreq-nvmem cpufreq
drivers (Viresh Kumar).
- Clean up the cpufreq core, the intel_pstate driver and the
schedutil cpufreq governor (Rafael Wysocki).
- Fix up error code paths in the sti-cpufreq and mediatek cpufreq
drivers (Yangtao Li, Qinglang Miao).
- Fix cpufreq_online() to return error codes instead of success (0)
in all cases when it fails (Wang ShaoBo).
- Add mt8167 support to the mediatek cpufreq driver and blacklist
mt8516 in the cpufreq-dt-platdev driver (Fabien Parent).
- Modify the tegra194 cpufreq driver to always return values from the
frequency table as the current frequency and clean up that driver
(Sumit Gupta, Jon Hunter).
- Modify the arm_scmi cpufreq driver to allow it to discover the
power scale present in the performance protocol and provide this
information to the Energy Model (Lukasz Luba).
- Add missing MODULE_DEVICE_TABLE to several cpufreq drivers (Pali
Rohár).
- Clean up the CPPC cpufreq driver (Ionela Voinescu).
- Fix NVMEM_IMX_OCOTP dependency in the imx cpufreq driver (Arnd
Bergmann).
- Rework the poling interval selection for the polling state in
cpuidle (Mel Gorman).
- Enable suspend-to-idle for PSCI OSI mode in the PSCI cpuidle driver
(Ulf Hansson).
- Modify the OPP framework to support empty (node-less) OPP tables in
DT for passing dependency information (Nicola Mazzucato).
- Fix potential lockdep issue in the OPP core and clean up the OPP
core (Viresh Kumar).
- Modify dev_pm_opp_put_regulators() to accept a NULL argument and
update its users accordingly (Viresh Kumar).
- Add frequency changes tracepoint to devfreq (Matthias Kaehlcke).
- Add support for governor feature flags to devfreq, make devfreq
sysfs file permissions depend on the governor and clean up the
devfreq core (Chanwoo Choi).
- Clean up the tegra20 devfreq driver and deprecate it to allow
another driver based on EMC_STAT to be used instead of it (Dmitry
Osipenko).
- Add interconnect support to the tegra30 devfreq driver, allow it to
take the interconnect and OPP information from DT and clean it up
(Dmitry Osipenko).
- Add interconnect support to the exynos-bus devfreq driver along
with interconnect properties documentation (Sylwester Nawrocki).
- Add suport for AMD Fam17h and Fam19h processors to the RAPL power
capping driver (Victor Ding, Kim Phillips).
- Fix handling of overly long constraint names in the powercap
framework (Lukasz Luba).
- Fix the wakeup configuration handling for bridges in the ACPI
device power management core (Rafael Wysocki).
- Add support for using an abstract scale for power units in the
Energy Model (EM) and document it (Lukasz Luba).
- Add em_cpu_energy() micro-optimization to the EM (Pavankumar
Kondeti).
- Modify the generic power domains (genpd) framwework to support
suspend-to-idle (Ulf Hansson).
- Fix creation of debugfs nodes in genpd (Thierry Strudel).
- Clean up genpd (Lina Iyer).
- Clean up the core system-wide suspend code and make it print driver
flags for devices with debug enabled (Alex Shi, Patrice Chotard,
Chen Yu).
- Modify the ACPI system reboot code to make it prepare for system
power off to avoid confusing the platform firmware (Kai-Heng Feng).
- Update the pm-graph (multiple changes, mostly usability-related)
and cpupower (online and offline CPU information support) PM
utilities (Todd Brandt, Brahadambal Srinivasan)"
* tag 'pm-5.11-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: (86 commits)
cpufreq: Fix cpufreq_online() return value on errors
cpufreq: Fix up several kerneldoc comments
cpufreq: stats: Use local_clock() instead of jiffies
cpufreq: schedutil: Simplify sugov_update_next_freq()
cpufreq: intel_pstate: Simplify intel_cpufreq_update_pstate()
PM: domains: create debugfs nodes when adding power domains
opp: of: Allow empty opp-table with opp-shared
dt-bindings: opp: Allow empty OPP tables
media: venus: dev_pm_opp_put_*() accepts NULL argument
drm/panfrost: dev_pm_opp_put_*() accepts NULL argument
drm/lima: dev_pm_opp_put_*() accepts NULL argument
PM / devfreq: exynos: dev_pm_opp_put_*() accepts NULL argument
cpufreq: qcom-cpufreq-nvmem: dev_pm_opp_put_*() accepts NULL argument
cpufreq: dt: dev_pm_opp_put_regulators() accepts NULL argument
opp: Allow dev_pm_opp_put_*() APIs to accept NULL opp_table
opp: Don't create an OPP table from dev_pm_opp_get_opp_table()
cpufreq: dt: Don't (ab)use dev_pm_opp_get_opp_table() to create OPP table
opp: Reduce the size of critical section in _opp_kref_release()
PM / EM: Micro optimization in em_cpu_energy
cpufreq: arm_scmi: Discover the power scale in performance protocol
...
Core:
- Consolidation and robustness changes for irq time accounting
- Cleanup and consolidation of irq stats
- Remove the fasteoi IPI flow which has been proved useless
- Provide an interface for converting legacy interrupt mechanism into
irqdomains
Drivers:
The rare event of not having completely new chip driver code, just new
DT bindings and extensions of existing drivers to accomodate new
variants!
- Preliminary support for managed interrupts on platform devices
- Correctly identify allocation of MSIs proxyied by another device
- Generalise the Ocelot support to new SoCs
- Improve GICv4.1 vcpu entry, matching the corresponding KVM optimisation
- Work around spurious interrupts on Qualcomm PDC
- Random fixes and cleanups
Thanks,
tglx
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Merge tag 'irq-core-2020-12-15' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull irq updates from Thomas Gleixner:
"Generic interrupt and irqchips subsystem updates. Unusually, there is
not a single completely new irq chip driver, just new DT bindings and
extensions of existing drivers to accomodate new variants!
Core:
- Consolidation and robustness changes for irq time accounting
- Cleanup and consolidation of irq stats
- Remove the fasteoi IPI flow which has been proved useless
- Provide an interface for converting legacy interrupt mechanism into
irqdomains
Drivers:
- Preliminary support for managed interrupts on platform devices
- Correctly identify allocation of MSIs proxyied by another device
- Generalise the Ocelot support to new SoCs
- Improve GICv4.1 vcpu entry, matching the corresponding KVM
optimisation
- Work around spurious interrupts on Qualcomm PDC
- Random fixes and cleanups"
* tag 'irq-core-2020-12-15' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (54 commits)
irqchip/qcom-pdc: Fix phantom irq when changing between rising/falling
driver core: platform: Add devm_platform_get_irqs_affinity()
ACPI: Drop acpi_dev_irqresource_disabled()
resource: Add irqresource_disabled()
genirq/affinity: Add irq_update_affinity_desc()
irqchip/gic-v3-its: Flag device allocation as proxied if behind a PCI bridge
irqchip/gic-v3-its: Tag ITS device as shared if allocating for a proxy device
platform-msi: Track shared domain allocation
irqchip/ti-sci-intr: Fix freeing of irqs
irqchip/ti-sci-inta: Fix printing of inta id on probe success
drivers/irqchip: Remove EZChip NPS interrupt controller
Revert "genirq: Add fasteoi IPI flow"
irqchip/hip04: Make IPIs use handle_percpu_devid_irq()
irqchip/bcm2836: Make IPIs use handle_percpu_devid_irq()
irqchip/armada-370-xp: Make IPIs use handle_percpu_devid_irq()
irqchip/gic, gic-v3: Make SGIs use handle_percpu_devid_irq()
irqchip/ocelot: Add support for Jaguar2 platforms
irqchip/ocelot: Add support for Serval platforms
irqchip/ocelot: Add support for Luton platforms
irqchip/ocelot: prepare to support more SoC
...
First off, some cpufreq drivers (eg. intel_pstate) can pass hints
beyond the current target frequency to the hardware and there are no
provisions for doing that in the cpufreq framework. In particular,
today the driver has to assume that it should not allow the frequency
to fall below the one requested by the governor (or the required
capacity may not be provided) which may not be the case and which may
lead to excessive energy usage in some scenarios.
Second, the hints passed by these drivers to the hardware need not be
in terms of the frequency, so representing the utilization numbers
coming from the scheduler as frequency before passing them to those
drivers is not really useful.
Address the two points above by adding a special-purpose replacement
for the ->fast_switch callback, called ->adjust_perf, allowing the
governor to pass abstract performance level (rather than frequency)
values for the minimum (required) and target (desired) performance
along with the CPU capacity to compare them to.
Also update the schedutil governor to use the new callback instead
of ->fast_switch if present and if the utilization mertics are
frequency-invariant (that is requisite for the direct mapping
between the utilization and the CPU performance levels to be a
reasonable approximation).
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Instead of passing util and max between functions while computing the
utilization and capacity, store the former in struct sg_cpu (along
with the latter and bw_dl).
This will allow the current utilization value to be compared with the
one obtained previously (which is requisite for some code changes to
follow this one), but also it causes the code to look slightly more
consistent and cleaner.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
- PSCI relay at EL2 when "protected KVM" is enabled
- New exception injection code
- Simplification of AArch32 system register handling
- Fix PMU accesses when no PMU is enabled
- Expose CSV3 on non-Meltdown hosts
- Cache hierarchy discovery fixes
- PV steal-time cleanups
- Allow function pointers at EL2
- Various host EL2 entry cleanups
- Simplification of the EL2 vector allocation
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Merge tag 'kvmarm-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into HEAD
KVM/arm64 updates for Linux 5.11
- PSCI relay at EL2 when "protected KVM" is enabled
- New exception injection code
- Simplification of AArch32 system register handling
- Fix PMU accesses when no PMU is enabled
- Expose CSV3 on non-Meltdown hosts
- Cache hierarchy discovery fixes
- PV steal-time cleanups
- Allow function pointers at EL2
- Various host EL2 entry cleanups
- Simplification of the EL2 vector allocation
The kernel test robot measured a -1.6% performance regression on
will-it-scale/sched_yield due to commit:
2558aacff8 ("sched/hotplug: Ensure only per-cpu kthreads run during hotplug")
Even though we were careful to replace a single load with another
single load from the same cacheline.
Restore finish_lock_switch() to the exact state before the offending
patch and solve the problem differently.
Fixes: 2558aacff8 ("sched/hotplug: Ensure only per-cpu kthreads run during hotplug")
Reported-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20201210161408.GX3021@hirez.programming.kicks-ass.net
- Preliminary support for managed interrupts on platform devices
- Correctly identify allocation of MSIs proxyied by another device
- Remove the fasteoi IPI flow which has been proved useless
- Generalise the Ocelot support to new SoCs
- Improve GICv4.1 vcpu entry, matching the corresponding KVM optimisation
- Work around spurious interrupts on Qualcomm PDC
- Random fixes and cleanups
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Merge tag 'irqchip-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms into irq/core
Pull irqchip updates for 5.11 from Marc Zyngier:
- Preliminary support for managed interrupts on platform devices
- Correctly identify allocation of MSIs proxyied by another device
- Remove the fasteoi IPI flow which has been proved useless
- Generalise the Ocelot support to new SoCs
- Improve GICv4.1 vcpu entry, matching the corresponding KVM optimisation
- Work around spurious interrupts on Qualcomm PDC
- Random fixes and cleanups
Link: https://lore.kernel.org/r/20201212135626.1479884-1-maz@kernel.org
- Consolidate all kmap_atomic() internals into a generic implementation
which builds the base for the kmap_local() API and make the
kmap_atomic() interface wrappers which handle the disabling/enabling of
preemption and pagefaults.
- Switch the storage from per-CPU to per task and provide scheduler
support for clearing mapping when scheduling out and restoring them
when scheduling back in.
- Merge the migrate_disable/enable() code, which is also part of the
scheduler pull request. This was required to make the kmap_local()
interface available which does not disable preemption when a mapping
is established. It has to disable migration instead to guarantee that
the virtual address of the mapped slot is the same accross preemption.
- Provide better debug facilities: guard pages and enforced utilization
of the mapping mechanics on 64bit systems when the architecture allows
it.
- Provide the new kmap_local() API which can now be used to cleanup the
kmap_atomic() usage sites all over the place. Most of the usage sites
do not require the implicit disabling of preemption and pagefaults so
the penalty on 64bit and 32bit non-highmem systems is removed and quite
some of the code can be simplified. A wholesale conversion is not
possible because some usage depends on the implicit side effects and
some need to be cleaned up because they work around these side effects.
The migrate disable side effect is only effective on highmem systems
and when enforced debugging is enabled. On 64bit and 32bit non-highmem
systems the overhead is completely avoided.
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Merge tag 'core-mm-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull kmap updates from Thomas Gleixner:
"The new preemtible kmap_local() implementation:
- Consolidate all kmap_atomic() internals into a generic
implementation which builds the base for the kmap_local() API and
make the kmap_atomic() interface wrappers which handle the
disabling/enabling of preemption and pagefaults.
- Switch the storage from per-CPU to per task and provide scheduler
support for clearing mapping when scheduling out and restoring them
when scheduling back in.
- Merge the migrate_disable/enable() code, which is also part of the
scheduler pull request. This was required to make the kmap_local()
interface available which does not disable preemption when a
mapping is established. It has to disable migration instead to
guarantee that the virtual address of the mapped slot is the same
across preemption.
- Provide better debug facilities: guard pages and enforced
utilization of the mapping mechanics on 64bit systems when the
architecture allows it.
- Provide the new kmap_local() API which can now be used to cleanup
the kmap_atomic() usage sites all over the place. Most of the usage
sites do not require the implicit disabling of preemption and
pagefaults so the penalty on 64bit and 32bit non-highmem systems is
removed and quite some of the code can be simplified. A wholesale
conversion is not possible because some usage depends on the
implicit side effects and some need to be cleaned up because they
work around these side effects.
The migrate disable side effect is only effective on highmem
systems and when enforced debugging is enabled. On 64bit and 32bit
non-highmem systems the overhead is completely avoided"
* tag 'core-mm-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (33 commits)
ARM: highmem: Fix cache_is_vivt() reference
x86/crashdump/32: Simplify copy_oldmem_page()
io-mapping: Provide iomap_local variant
mm/highmem: Provide kmap_local*
sched: highmem: Store local kmaps in task struct
x86: Support kmap_local() forced debugging
mm/highmem: Provide CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP
mm/highmem: Provide and use CONFIG_DEBUG_KMAP_LOCAL
microblaze/mm/highmem: Add dropped #ifdef back
xtensa/mm/highmem: Make generic kmap_atomic() work correctly
mm/highmem: Take kmap_high_get() properly into account
highmem: High implementation details and document API
Documentation/io-mapping: Remove outdated blurb
io-mapping: Cleanup atomic iomap
mm/highmem: Remove the old kmap_atomic cruft
highmem: Get rid of kmap_types.h
xtensa/mm/highmem: Switch to generic kmap atomic
sparc/mm/highmem: Switch to generic kmap atomic
powerpc/mm/highmem: Switch to generic kmap atomic
nds32/mm/highmem: Switch to generic kmap atomic
...
- migrate_disable/enable() support which originates from the RT tree and
is now a prerequisite for the new preemptible kmap_local() API which aims
to replace kmap_atomic().
- A fair amount of topology and NUMA related improvements
- Improvements for the frequency invariant calculations
- Enhanced robustness for the global CPU priority tracking and decision
making
- The usual small fixes and enhancements all over the place
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Merge tag 'sched-core-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Thomas Gleixner:
- migrate_disable/enable() support which originates from the RT tree
and is now a prerequisite for the new preemptible kmap_local() API
which aims to replace kmap_atomic().
- A fair amount of topology and NUMA related improvements
- Improvements for the frequency invariant calculations
- Enhanced robustness for the global CPU priority tracking and decision
making
- The usual small fixes and enhancements all over the place
* tag 'sched-core-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (61 commits)
sched/fair: Trivial correction of the newidle_balance() comment
sched/fair: Clear SMT siblings after determining the core is not idle
sched: Fix kernel-doc markup
x86: Print ratio freq_max/freq_base used in frequency invariance calculations
x86, sched: Use midpoint of max_boost and max_P for frequency invariance on AMD EPYC
x86, sched: Calculate frequency invariance for AMD systems
irq_work: Optimize irq_work_single()
smp: Cleanup smp_call_function*()
irq_work: Cleanup
sched: Limit the amount of NUMA imbalance that can exist at fork time
sched/numa: Allow a floating imbalance between NUMA nodes
sched: Avoid unnecessary calculation of load imbalance at clone time
sched/numa: Rename nr_running and break out the magic number
sched: Make migrate_disable/enable() independent of RT
sched/topology: Condition EAS enablement on FIE support
arm64: Rebuild sched domains on invariance status changes
sched/topology,schedutil: Wrap sched domains rebuild
sched/uclamp: Allow to reset a task uclamp constraint value
sched/core: Fix typos in comments
Documentation: scheduler: fix information on arch SD flags, sched_domain and sched_debug
...
- More generalization of entry/exit functionality
- The consolidation work to reclaim TIF flags on x86 and also for non-x86
specific TIF flags which are solely relevant for syscall related work
and have been moved into their own storage space. The x86 specific part
had to be merged in to avoid a major conflict.
- The TIF_NOTIFY_SIGNAL work which replaces the inefficient signal
delivery mode of task work and results in an impressive performance
improvement for io_uring. The non-x86 consolidation of this is going to
come seperate via Jens.
- The selective syscall redirection facility which provides a clean and
efficient way to support the non-Linux syscalls of WINE by catching them
at syscall entry and redirecting them to the user space emulation. This
can be utilized for other purposes as well and has been designed
carefully to avoid overhead for the regular fastpath. This includes the
core changes and the x86 support code.
- Simplification of the context tracking entry/exit handling for the users
of the generic entry code which guarantee the proper ordering and
protection.
- Preparatory changes to make the generic entry code accomodate S390
specific requirements which are mostly related to their syscall restart
mechanism.
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Merge tag 'core-entry-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull core entry/exit updates from Thomas Gleixner:
"A set of updates for entry/exit handling:
- More generalization of entry/exit functionality
- The consolidation work to reclaim TIF flags on x86 and also for
non-x86 specific TIF flags which are solely relevant for syscall
related work and have been moved into their own storage space. The
x86 specific part had to be merged in to avoid a major conflict.
- The TIF_NOTIFY_SIGNAL work which replaces the inefficient signal
delivery mode of task work and results in an impressive performance
improvement for io_uring. The non-x86 consolidation of this is
going to come seperate via Jens.
- The selective syscall redirection facility which provides a clean
and efficient way to support the non-Linux syscalls of WINE by
catching them at syscall entry and redirecting them to the user
space emulation. This can be utilized for other purposes as well
and has been designed carefully to avoid overhead for the regular
fastpath. This includes the core changes and the x86 support code.
- Simplification of the context tracking entry/exit handling for the
users of the generic entry code which guarantee the proper ordering
and protection.
- Preparatory changes to make the generic entry code accomodate S390
specific requirements which are mostly related to their syscall
restart mechanism"
* tag 'core-entry-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (36 commits)
entry: Add syscall_exit_to_user_mode_work()
entry: Add exit_to_user_mode() wrapper
entry_Add_enter_from_user_mode_wrapper
entry: Rename exit_to_user_mode()
entry: Rename enter_from_user_mode()
docs: Document Syscall User Dispatch
selftests: Add benchmark for syscall user dispatch
selftests: Add kselftest for syscall user dispatch
entry: Support Syscall User Dispatch on common syscall entry
kernel: Implement selective syscall userspace redirection
signal: Expose SYS_USER_DISPATCH si_code type
x86: vdso: Expose sigreturn address on vdso to the kernel
MAINTAINERS: Add entry for common entry code
entry: Fix boot for !CONFIG_GENERIC_ENTRY
x86: Support HAVE_CONTEXT_TRACKING_OFFSTACK
context_tracking: Only define schedule_user() on !HAVE_CONTEXT_TRACKING_OFFSTACK archs
sched: Detect call to schedule from critical entry code
context_tracking: Don't implement exception_enter/exit() on CONFIG_HAVE_CONTEXT_TRACKING_OFFSTACK
context_tracking: Introduce HAVE_CONTEXT_TRACKING_OFFSTACK
x86: Reclaim unused x86 TI flags
...
Rearrange a conditional to make it more straightforward.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
idle_balance() has been renamed to newidle_balance(). To differentiate
with nohz_idle_balance, it seems refining the comment will be helpful
for the readers of the code.
Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20201202220641.22752-1-song.bao.hua@hisilicon.com
The clearing of SMT siblings from the SIS mask before checking for an idle
core is a small but unnecessary cost. Defer the clearing of the siblings
until the scan moves to the next potential target. The cost of this was
not measured as it is borderline noise but it should be self-evident.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20201130144020.GS3371@techsingularity.net
Kernel-doc requires that a kernel-doc markup to be immediately
below the function prototype, as otherwise it will rename it.
So, move sys_sched_yield() markup to the right place.
Also fix the cpu_util() markup: Kernel-doc markups
should use this format:
identifier - description
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/50cd6f460aeb872ebe518a8e9cfffda2df8bdb0a.1606823973.git.mchehab+huawei@kernel.org
membarrier()'s MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE is documented as
syncing the core on all sibling threads but not necessarily the calling
thread. This behavior is fundamentally buggy and cannot be used safely.
Suppose a user program has two threads. Thread A is on CPU 0 and thread B
is on CPU 1. Thread A modifies some text and calls
membarrier(MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE).
Then thread B executes the modified code. If, at any point after
membarrier() decides which CPUs to target, thread A could be preempted and
replaced by thread B on CPU 0. This could even happen on exit from the
membarrier() syscall. If this happens, thread B will end up running on CPU
0 without having synced.
In principle, this could be fixed by arranging for the scheduler to issue
sync_core_before_usermode() whenever switching between two threads in the
same mm if there is any possibility of a concurrent membarrier() call, but
this would have considerable overhead. Instead, make membarrier() sync the
calling CPU as well.
As an optimization, this avoids an extra smp_mb() in the default
barrier-only mode and an extra rseq preempt on the caller.
Fixes: 70216e18e5 ("membarrier: Provide core serializing command, *_SYNC_CORE")
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/r/250ded637696d490c69bef1877148db86066881c.1607058304.git.luto@kernel.org
membarrier() does not explicitly sync_core() remote CPUs; instead, it
relies on the assumption that an IPI will result in a core sync. On x86,
this may be true in practice, but it's not architecturally reliable. In
particular, the SDM and APM do not appear to guarantee that interrupt
delivery is serializing. While IRET does serialize, IPI return can
schedule, thereby switching to another task in the same mm that was
sleeping in a syscall. The new task could then SYSRET back to usermode
without ever executing IRET.
Make this more robust by explicitly calling sync_core_before_usermode()
on remote cores. (This also helps people who search the kernel tree for
instances of sync_core() and sync_core_before_usermode() -- one might be
surprised that the core membarrier code doesn't currently show up in a
such a search.)
Fixes: 70216e18e5 ("membarrier: Provide core serializing command, *_SYNC_CORE")
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/776b448d5f7bd6b12690707f5ed67bcda7f1d427.1607058304.git.luto@kernel.org
It seems that most RSEQ membarrier users will expect any stores done before
the membarrier() syscall to be visible to the target task(s). While this
is extremely likely to be true in practice, nothing actually guarantees it
by a strict reading of the x86 manuals. Rather than providing this
guarantee by accident and potentially causing a problem down the road, just
add an explicit barrier.
Fixes: 70216e18e5 ("membarrier: Provide core serializing command, *_SYNC_CORE")
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/d3e7197e034fa4852afcf370ca49c30496e58e40.1607058304.git.luto@kernel.org
IRQ time entry is currently accounted before HARDIRQ_OFFSET or
SOFTIRQ_OFFSET are incremented. This is convenient to decide to which
index the cputime to account is dispatched.
Unfortunately it prevents tick_irq_enter() from being called under
HARDIRQ_OFFSET because tick_irq_enter() has to be called before the IRQ
entry accounting due to the necessary clock catch up. As a result we
don't benefit from appropriate lockdep coverage on tick_irq_enter().
To prepare for fixing this, move the IRQ entry cputime accounting after
the preempt offset is incremented. This requires the cputime dispatch
code to handle the extra offset.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20201202115732.27827-5-frederic@kernel.org
The 3 architectures implementing CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
all have their own version of irq time accounting that dispatch the
cputime to the appropriate index: hardirq, softirq, system, idle,
guest... from an all-in-one function.
Instead of having these ad-hoc versions, move the cputime destination
dispatch decision to the core code and leave only the actual per-index
cputime accounting to the architecture.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201202115732.27827-4-frederic@kernel.org
s390 has its own version of IRQ entry accounting because it doesn't
account the idle time the same way the other architectures do. Only
the actual idle sleep time is accounted as idle time, the rest of the
idle task execution is accounted as system time.
Make the generic IRQ entry accounting aware of architectures that have
their own way of accounting idle time and convert s390 to use it.
This prepares s390 to get involved in further consolidations of IRQ
time accounting.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201202115732.27827-3-frederic@kernel.org
account_irq_enter_time() and account_irq_exit_time() are not called
from modules. EXPORT_SYMBOL_GPL() can be safely removed from the IRQ
cputime accounting functions called from there.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201202115732.27827-2-frederic@kernel.org
idle path. Similar to the entry path the low level idle functions have to
be non-instrumentable.
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Merge tag 'locking-urgent-2020-11-29' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking fixes from Thomas Gleixner:
"Two more places which invoke tracing from RCU disabled regions in the
idle path.
Similar to the entry path the low level idle functions have to be
non-instrumentable"
* tag 'locking-urgent-2020-11-29' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
intel_idle: Fix intel_idle() vs tracing
sched/idle: Fix arch_cpu_idle() vs tracing
Get rid of the __call_single_node union and cleanup the API a little
to avoid external code relying on the structure layout as much.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
At fork time currently, a local node can be allowed to fill completely
and allow the periodic load balancer to fix the problem. This can be
problematic in cases where a task creates lots of threads that idle until
woken as part of a worker poll causing a memory bandwidth problem.
However, a "real" workload suffers badly from this behaviour. The workload
in question is mostly NUMA aware but spawns large numbers of threads
that act as a worker pool that can be called from anywhere. These need
to spread early to get reasonable behaviour.
This patch limits how much a local node can fill before spilling over
to another node and it will not be a universal win. Specifically,
very short-lived workloads that fit within a NUMA node would prefer
the memory bandwidth.
As I cannot describe the "real" workload, the best proxy measure I found
for illustration was a page fault microbenchmark. It's not representative
of the workload but demonstrates the hazard of the current behaviour.
pft timings
5.10.0-rc2 5.10.0-rc2
imbalancefloat-v2 forkspread-v2
Amean elapsed-1 46.37 ( 0.00%) 46.05 * 0.69%*
Amean elapsed-4 12.43 ( 0.00%) 12.49 * -0.47%*
Amean elapsed-7 7.61 ( 0.00%) 7.55 * 0.81%*
Amean elapsed-12 4.79 ( 0.00%) 4.80 ( -0.17%)
Amean elapsed-21 3.13 ( 0.00%) 2.89 * 7.74%*
Amean elapsed-30 3.65 ( 0.00%) 2.27 * 37.62%*
Amean elapsed-48 3.08 ( 0.00%) 2.13 * 30.69%*
Amean elapsed-79 2.00 ( 0.00%) 1.90 * 4.95%*
Amean elapsed-80 2.00 ( 0.00%) 1.90 * 4.70%*
This is showing the time to fault regions belonging to threads. The target
machine has 80 logical CPUs and two nodes. Note the ~30% gain when the
machine is approximately the point where one node becomes fully utilised.
The slower results are borderline noise.
Kernel building shows similar benefits around the same balance point.
Generally performance was either neutral or better in the tests conducted.
The main consideration with this patch is the point where fork stops
spreading a task so some workloads may benefit from different balance
points but it would be a risky tuning parameter.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20201120090630.3286-5-mgorman@techsingularity.net
Currently, an imbalance is only allowed when a destination node
is almost completely idle. This solved one basic class of problems
and was the cautious approach.
This patch revisits the possibility that NUMA nodes can be imbalanced
until 25% of the CPUs are occupied. The reasoning behind 25% is somewhat
superficial -- it's half the cores when HT is enabled. At higher
utilisations, balancing should continue as normal and keep things even
until scheduler domains are fully busy or over utilised.
Note that this is not expected to be a universal win. Any benchmark
that prefers spreading as wide as possible with limited communication
will favour the old behaviour as there is more memory bandwidth.
Workloads that communicate heavily in pairs such as netperf or tbench
benefit. For the tests I ran, the vast majority of workloads saw
a benefit so it seems to be a worthwhile trade-off.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20201120090630.3286-4-mgorman@techsingularity.net
In find_idlest_group(), the load imbalance is only relevant when the group
is either overloaded or fully busy but it is calculated unconditionally.
This patch moves the imbalance calculation to the context it is required.
Technically, it is a micro-optimisation but really the benefit is avoiding
confusing one type of imbalance with another depending on the group_type
in the next patch.
No functional change.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20201120090630.3286-3-mgorman@techsingularity.net
This is simply a preparation patch to make the following patches easier
to read. No functional change.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20201120090630.3286-2-mgorman@techsingularity.net
We call arch_cpu_idle() with RCU disabled, but then use
local_irq_{en,dis}able(), which invokes tracing, which relies on RCU.
Switch all arch_cpu_idle() implementations to use
raw_local_irq_{en,dis}able() and carefully manage the
lockdep,rcu,tracing state like we do in entry.
(XXX: we really should change arch_cpu_idle() to not return with
interrupts enabled)
Reported-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lkml.kernel.org/r/20201120114925.594122626@infradead.org
Instead of storing the map per CPU provide and use per task storage. That
prepares for local kmaps which are preemptible.
The context switch code is preparatory and not yet in use because
kmap_atomic() runs with preemption disabled. Will be made usable in the
next step.
The context switch logic is safe even when an interrupt happens after
clearing or before restoring the kmaps. The kmap index in task struct is
not modified so any nesting kmap in an interrupt will use unused indices
and on return the counter is the same as before.
Also add an assert into the return to user space code. Going back to user
space with an active kmap local is a nono.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20201118204007.372935758@linutronix.de
Now that the scheduler can deal with migrate disable properly, there is no
real compelling reason to make it only available for RT.
There are quite some code pathes which needlessly disable preemption in
order to prevent migration and some constructs like kmap_atomic() enforce
it implicitly.
Making it available independent of RT allows to provide a preemptible
variant of kmap_atomic() and makes the code more consistent in general.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Grudgingly-Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20201118204007.269943012@linutronix.de
- Make the conditional update of the overutilized state work correctly by
caching the relevant flags state before overwriting them and checking
them afterwards.
- Fix a data race in the wakeup path which caused loadavg on ARM64
platforms to become a random number generator.
- Fix the ordering of the iowaiter accounting operations so it can't be
decremented before it is incremented.
- Fix a bug in the deadline scheduler vs. priority inheritance when a
non-deadline task A has inherited the parameters of a deadline task B
and then blocks on a non-deadline task C.
The second inheritance step used the static deadline parameters of task
A, which are usually 0, instead of further propagating task B's
parameters. The zero initialized parameters trigger a bug in the
deadline scheduler.
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Merge tag 'sched-urgent-2020-11-22' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler fixes from Thomas Gleixner:
"A couple of scheduler fixes:
- Make the conditional update of the overutilized state work
correctly by caching the relevant flags state before overwriting
them and checking them afterwards.
- Fix a data race in the wakeup path which caused loadavg on ARM64
platforms to become a random number generator.
- Fix the ordering of the iowaiter accounting operations so it can't
be decremented before it is incremented.
- Fix a bug in the deadline scheduler vs. priority inheritance when a
non-deadline task A has inherited the parameters of a deadline task
B and then blocks on a non-deadline task C.
The second inheritance step used the static deadline parameters of
task A, which are usually 0, instead of further propagating task
B's parameters. The zero initialized parameters trigger a bug in
the deadline scheduler"
* tag 'sched-urgent-2020-11-22' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/deadline: Fix priority inheritance with multiple scheduling classes
sched: Fix rq->nr_iowait ordering
sched: Fix data-race in wakeup
sched/fair: Fix overutilized update in enqueue_task_fair()
In order to make accurate predictions across CPUs and for all performance
states, Energy Aware Scheduling (EAS) needs frequency-invariant load
tracking signals.
EAS task placement aims to minimize energy consumption, and does so in
part by limiting the search space to only CPUs with the highest spare
capacity (CPU capacity - CPU utilization) in their performance domain.
Those candidates are the placement choices that will keep frequency at
its lowest possible and therefore save the most energy.
But without frequency invariance, a CPU's utilization is relative to the
CPU's current performance level, and not relative to its maximum
performance level, which determines its capacity. As a result, it will
fail to correctly indicate any potential spare capacity obtained by an
increase in a CPU's performance level. Therefore, a non-invariant
utilization signal would render the EAS task placement logic invalid.
Now that we properly report support for the Frequency Invariance Engine
(FIE) through arch_scale_freq_invariant() for arm and arm64 systems,
while also ensuring a re-evaluation of the EAS use conditions for
possible invariance status change, we can assert this is the case when
initializing EAS. Warn and bail out otherwise.
Suggested-by: Quentin Perret <qperret@google.com>
Signed-off-by: Ionela Voinescu <ionela.voinescu@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20201027180713.7642-4-ionela.voinescu@arm.com
Add the rebuild_sched_domains_energy() function to wrap the functionality
that rebuilds the scheduling domains if any of the Energy Aware Scheduling
(EAS) initialisation conditions change. This functionality is used when
schedutil is added or removed or when EAS is enabled or disabled
through the sched_energy_aware sysctl.
Therefore, create a single function that is used in both these cases and
that can be later reused.
Signed-off-by: Ionela Voinescu <ionela.voinescu@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Quentin Perret <qperret@google.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lkml.kernel.org/r/20201027180713.7642-2-ionela.voinescu@arm.com
In case the user wants to stop controlling a uclamp constraint value
for a task, use the magic value -1 in sched_util_{min,max} with the
appropriate sched_flags (SCHED_FLAG_UTIL_CLAMP_{MIN,MAX}) to indicate
the reset.
The advantage over the 'additional flag' approach (i.e. introducing
SCHED_FLAG_UTIL_CLAMP_RESET) is that no additional flag has to be
exported via uapi. This avoids the need to document how this new flag
has be used in conjunction with the existing uclamp related flags.
The following subtle issue is fixed as well. When a uclamp constraint
value is set on a !user_defined uclamp_se it is currently first reset
and then set.
Fix this by AND'ing !user_defined with !SCHED_FLAG_UTIL_CLAMP which
stands for the 'sched class change' case.
The related condition 'if (uc_se->user_defined)' moved from
__setscheduler_uclamp() into uclamp_reset().
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Yun Hsiang <hsiang023167@gmail.com>
Link: https://lkml.kernel.org/r/20201113113454.25868-1-dietmar.eggemann@arm.com
NUMA topologies where the shortest path between some two nodes requires
three or more hops (i.e. diameter > 2) end up being misrepresented in the
scheduler topology structures.
This is currently detected when booting a kernel with CONFIG_SCHED_DEBUG=y
+ sched_debug on the cmdline, although this will only yield a warning about
sched_group spans not matching sched_domain spans:
ERROR: groups don't span domain->span
Add an explicit warning for that case, triggered regardless of
CONFIG_SCHED_DEBUG, and decorate it with an appropriate comment.
The topology described in the comment can be booted up on QEMU by appending
the following to your usual QEMU incantation:
-smp cores=4 \
-numa node,cpus=0,nodeid=0 -numa node,cpus=1,nodeid=1, \
-numa node,cpus=2,nodeid=2, -numa node,cpus=3,nodeid=3, \
-numa dist,src=0,dst=1,val=20, -numa dist,src=0,dst=2,val=30, \
-numa dist,src=0,dst=3,val=40, -numa dist,src=1,dst=2,val=20, \
-numa dist,src=1,dst=3,val=30, -numa dist,src=2,dst=3,val=20
A somewhat more realistic topology (6-node mesh) with the same affliction
can be conjured with:
-smp cores=6 \
-numa node,cpus=0,nodeid=0 -numa node,cpus=1,nodeid=1, \
-numa node,cpus=2,nodeid=2, -numa node,cpus=3,nodeid=3, \
-numa node,cpus=4,nodeid=4, -numa node,cpus=5,nodeid=5, \
-numa dist,src=0,dst=1,val=20, -numa dist,src=0,dst=2,val=30, \
-numa dist,src=0,dst=3,val=40, -numa dist,src=0,dst=4,val=30, \
-numa dist,src=0,dst=5,val=20, \
-numa dist,src=1,dst=2,val=20, -numa dist,src=1,dst=3,val=30, \
-numa dist,src=1,dst=4,val=20, -numa dist,src=1,dst=5,val=30, \
-numa dist,src=2,dst=3,val=20, -numa dist,src=2,dst=4,val=30, \
-numa dist,src=2,dst=5,val=40, \
-numa dist,src=3,dst=4,val=20, -numa dist,src=3,dst=5,val=30, \
-numa dist,src=4,dst=5,val=20
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Link: https://lore.kernel.org/lkml/jhjtux5edo2.mognet@arm.com
Oleksandr reported hitting the WARN in the 'task_rq(p) != rq' branch
of migration_cpu_stop(). Valentin noted that using cpu_of(rq) in that
case is just plain wrong to begin with, since per the earlier branch
that isn't the actual CPU of the task.
Replace both instances of is_cpu_allowed() by a direct p->cpus_mask
test using task_cpu().
Reported-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Debugged-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Qian reported that some fuzzer issuing sched_setaffinity() ends up stuck on
a wait_for_completion(). The problematic pattern seems to be:
affine_move_task()
// task_running() case
stop_one_cpu();
wait_for_completion(&pending->done);
Combined with, on the stopper side:
migration_cpu_stop()
// Task moved between unlocks and scheduling the stopper
task_rq(p) != rq &&
// task_running() case
dest_cpu >= 0
=> no complete_all()
This can happen with both PREEMPT and !PREEMPT, although !PREEMPT should
be more likely to see this given the targeted task has a much bigger window
to block and be woken up elsewhere before the stopper runs.
Make migration_cpu_stop() always look at pending affinity requests; signal
their completion if the stopper hits a rq mismatch but the task is
still within its allowed mask. When Migrate-Disable isn't involved, this
matches the previous set_cpus_allowed_ptr() vs migration_cpu_stop()
behaviour.
Fixes: 6d337eab04 ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Reported-by: Qian Cai <cai@redhat.com>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/lkml/8b62fd1ad1b18def27f18e2ee2df3ff5b36d0762.camel@redhat.com
schedule_user() was traditionally used by the entry code's tail to
preempt userspace after the call to user_enter(). Indeed the call to
user_enter() used to be performed upon syscall exit slow path which was
right before the last opportunity to schedule() while resuming to
userspace. The context tracking state had to be saved on the task stack
and set back to CONTEXT_KERNEL temporarily in order to safely switch to
another task.
Only a few archs use it now (namely sparc64 and powerpc64) and those
implementing HAVE_CONTEXT_TRACKING_OFFSTACK definetly can't rely on it.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20201117151637.259084-5-frederic@kernel.org
