select_task_rq() is used in a few paths to select the CPU upon which a
thread should be run - for example it is used by try_to_wake_up() & by
fork or exec balancing. As-is it allows use of any online CPU that is
present in the task's cpus_allowed mask.
This presents a problem because there is a period whilst CPUs are
brought online where a CPU is marked online, but is not yet fully
initialized - ie. the period where CPUHP_AP_ONLINE_IDLE <= state <
CPUHP_ONLINE. Usually we don't run any user tasks during this window,
but there are corner cases where this can happen. An example observed
is:
- Some user task A, running on CPU X, forks to create task B.
- sched_fork() calls __set_task_cpu() with cpu=X, setting task B's
task_struct::cpu field to X.
- CPU X is offlined.
- Task A, currently somewhere between the __set_task_cpu() in
copy_process() and the call to wake_up_new_task(), is migrated to
CPU Y by migrate_tasks() when CPU X is offlined.
- CPU X is onlined, but still in the CPUHP_AP_ONLINE_IDLE state. The
scheduler is now active on CPU X, but there are no user tasks on
the runqueue.
- Task A runs on CPU Y & reaches wake_up_new_task(). This calls
select_task_rq() with cpu=X, taken from task B's task_struct,
and select_task_rq() allows CPU X to be returned.
- Task A enqueues task B on CPU X's runqueue, via activate_task() &
enqueue_task().
- CPU X now has a user task on its runqueue before it has reached the
CPUHP_ONLINE state.
In most cases, the user tasks that schedule on the newly onlined CPU
have no idea that anything went wrong, but one case observed to be
problematic is if the task goes on to invoke the sched_setaffinity
syscall. The newly onlined CPU reaches the CPUHP_AP_ONLINE_IDLE state
before the CPU that brought it online calls stop_machine_unpark(). This
means that for a portion of the window of time between
CPUHP_AP_ONLINE_IDLE & CPUHP_ONLINE the newly onlined CPU's struct
cpu_stopper has its enabled field set to false. If a user thread is
executed on the CPU during this window and it invokes sched_setaffinity
with a CPU mask that does not include the CPU it's running on, then when
__set_cpus_allowed_ptr() calls stop_one_cpu() intending to invoke
migration_cpu_stop() and perform the actual migration away from the CPU
it will simply return -ENOENT rather than calling migration_cpu_stop().
We then return from the sched_setaffinity syscall back to the user task
that is now running on a CPU which it just asked not to run on, and
which is not present in its cpus_allowed mask.
This patch resolves the problem by having select_task_rq() enforce that
user tasks run on CPUs that are active - the same requirement that
select_fallback_rq() already enforces. This should ensure that newly
onlined CPUs reach the CPUHP_AP_ACTIVE state before being able to
schedule user tasks, and also implies that bringup_wait_for_ap() will
have called stop_machine_unpark() which resolves the sched_setaffinity
issue above.
I haven't yet investigated them, but it may be of interest to review
whether any of the actions performed by hotplug states between
CPUHP_AP_ONLINE_IDLE & CPUHP_AP_ACTIVE could have similar unintended
effects on user tasks that might schedule before they are reached, which
might widen the scope of the problem from just affecting the behaviour
of sched_setaffinity.
Signed-off-by: Paul Burton <paul.burton@mips.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20180526154648.11635-2-paul.burton@mips.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
As already enforced by the WARN() in __set_cpus_allowed_ptr(), the rules
for running on an online && !active CPU are stricter than just being a
kthread, you need to be a per-cpu kthread.
If you're not strictly per-CPU, you have better CPUs to run on and
don't need the partially booted one to get your work done.
The exception is to allow smpboot threads to bootstrap the CPU itself
and get kernel 'services' initialized before we allow userspace on it.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 955dbdf4ce ("sched: Allow migrating kthreads into online but inactive CPUs")
Link: http://lkml.kernel.org/r/20170725165821.cejhb7v2s3kecems@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
> kernel/sched/core.c:6921 cpu_weight_nice_write_s64() warn: potential spectre issue 'sched_prio_to_weight'
Userspace controls @nice, so sanitize the value before using it to
index an array.
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Gaurav reported a perceived problem with TASK_PARKED, which turned out
to be a broken wait-loop pattern in __kthread_parkme(), but the
reported issue can (and does) in fact happen for states that do not do
condition based sleeps.
When the 'current->state = TASK_RUNNING' store of a previous
(concurrent) try_to_wake_up() collides with the setting of a 'special'
sleep state, we can loose the sleep state.
Normal condition based wait-loops are immune to this problem, but for
sleep states that are not condition based are subject to this problem.
There already is a fix for TASK_DEAD. Abstract that and also apply it
to TASK_STOPPED and TASK_TRACED, both of which are also without
condition based wait-loop.
Reported-by: Gaurav Kohli <gkohli@codeaurora.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Even with the wait-loop fixed, there is a further issue with
kthread_parkme(). Upon hotplug, when we do takedown_cpu(),
smpboot_park_threads() can return before all those threads are in fact
blocked, due to the placement of the complete() in __kthread_parkme().
When that happens, sched_cpu_dying() -> migrate_tasks() can end up
migrating such a still runnable task onto another CPU.
Normally the task will have hit schedule() and gone to sleep by the
time we do kthread_unpark(), which will then do __kthread_bind() to
re-bind the task to the correct CPU.
However, when we loose the initial TASK_PARKED store to the concurrent
wakeup issue described previously, do the complete(), get migrated, it
is possible to either:
- observe kthread_unpark()'s clearing of SHOULD_PARK and terminate
the park and set TASK_RUNNING, or
- __kthread_bind()'s wait_task_inactive() to observe the competing
TASK_RUNNING store.
Either way the WARN() in __kthread_bind() will trigger and fail to
correctly set the CPU affinity.
Fix this by only issuing the complete() when the kthread has scheduled
out. This does away with all the icky 'still running' nonsense.
The alternative is to promote TASK_PARKED to a special state, this
guarantees wait_task_inactive() cannot observe a 'stale' TASK_RUNNING
and we'll end up doing the right thing, but this preserves the whole
icky business of potentially migating the still runnable thing.
Reported-by: Gaurav Kohli <gkohli@codeaurora.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Pull scheduler fixes from Thomas Gleixner:
"A few scheduler fixes:
- Prevent a bogus warning vs. runqueue clock update flags in
do_sched_rt_period_timer()
- Simplify the helper functions which handle requests for skipping
the runqueue clock updat.
- Do not unlock the tunables mutex in the error path of the cpu
frequency scheduler utils. Its not held.
- Enforce proper alignement for 'struct util_est' in sched_avg to
prevent a misalignment fault on IA64"
* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/core: Force proper alignment of 'struct util_est'
sched/core: Simplify helpers for rq clock update skip requests
sched/rt: Fix rq->clock_update_flags < RQCF_ACT_SKIP warning
sched/cpufreq/schedutil: Fix error path mutex unlock
KASAN splats indicate that in some cases we free a live mm, then
continue to access it, with potentially disastrous results. This is
likely due to a mismatched mmdrop() somewhere in the kernel, but so far
the culprit remains elusive.
Let's have __mmdrop() verify that the mm isn't live for the current
task, similar to the existing check for init_mm. This way, we can catch
this class of issue earlier, and without requiring KASAN.
Currently, idle_task_exit() leaves active_mm stale after it switches to
init_mm. This isn't harmful, but will trigger the new assertions, so we
must adjust idle_task_exit() to update active_mm.
Link: http://lkml.kernel.org/r/20180312140103.19235-1-mark.rutland@arm.com
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
By renaming the functions we can get rid of the skip parameter
and have better code redability. It makes zero sense to have
things such as:
rq_clock_skip_update(rq, false)
When the skip request is in fact not going to happen. Ever. Rename
things such that we end up with:
rq_clock_skip_update(rq)
rq_clock_cancel_skipupdate(rq)
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Cc: matt@codeblueprint.co.uk
Cc: rostedt@goodmis.org
Link: http://lkml.kernel.org/r/20180404161539.nhadkff2aats74jh@linux-n805
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Pull removal of in-kernel calls to syscalls from Dominik Brodowski:
"System calls are interaction points between userspace and the kernel.
Therefore, system call functions such as sys_xyzzy() or
compat_sys_xyzzy() should only be called from userspace via the
syscall table, but not from elsewhere in the kernel.
At least on 64-bit x86, it will likely be a hard requirement from
v4.17 onwards to not call system call functions in the kernel: It is
better to use use a different calling convention for system calls
there, where struct pt_regs is decoded on-the-fly in a syscall wrapper
which then hands processing over to the actual syscall function. This
means that only those parameters which are actually needed for a
specific syscall are passed on during syscall entry, instead of
filling in six CPU registers with random user space content all the
time (which may cause serious trouble down the call chain). Those
x86-specific patches will be pushed through the x86 tree in the near
future.
Moreover, rules on how data may be accessed may differ between kernel
data and user data. This is another reason why calling sys_xyzzy() is
generally a bad idea, and -- at most -- acceptable in arch-specific
code.
This patchset removes all in-kernel calls to syscall functions in the
kernel with the exception of arch/. On top of this, it cleans up the
three places where many syscalls are referenced or prototyped, namely
kernel/sys_ni.c, include/linux/syscalls.h and include/linux/compat.h"
* 'syscalls-next' of git://git.kernel.org/pub/scm/linux/kernel/git/brodo/linux: (109 commits)
bpf: whitelist all syscalls for error injection
kernel/sys_ni: remove {sys_,sys_compat} from cond_syscall definitions
kernel/sys_ni: sort cond_syscall() entries
syscalls/x86: auto-create compat_sys_*() prototypes
syscalls: sort syscall prototypes in include/linux/compat.h
net: remove compat_sys_*() prototypes from net/compat.h
syscalls: sort syscall prototypes in include/linux/syscalls.h
kexec: move sys_kexec_load() prototype to syscalls.h
x86/sigreturn: use SYSCALL_DEFINE0
x86: fix sys_sigreturn() return type to be long, not unsigned long
x86/ioport: add ksys_ioperm() helper; remove in-kernel calls to sys_ioperm()
mm: add ksys_readahead() helper; remove in-kernel calls to sys_readahead()
mm: add ksys_mmap_pgoff() helper; remove in-kernel calls to sys_mmap_pgoff()
mm: add ksys_fadvise64_64() helper; remove in-kernel call to sys_fadvise64_64()
fs: add ksys_fallocate() wrapper; remove in-kernel calls to sys_fallocate()
fs: add ksys_p{read,write}64() helpers; remove in-kernel calls to syscalls
fs: add ksys_truncate() wrapper; remove in-kernel calls to sys_truncate()
fs: add ksys_sync_file_range helper(); remove in-kernel calls to syscall
kernel: add ksys_setsid() helper; remove in-kernel call to sys_setsid()
kernel: add ksys_unshare() helper; remove in-kernel calls to sys_unshare()
...
Using the sched-internal do_sched_yield() helper allows us to get rid of
the sched-internal call to the sys_sched_yield() syscall.
This patch is part of a series which removes in-kernel calls to syscalls.
On this basis, the syscall entry path can be streamlined. For details, see
http://lkml.kernel.org/r/20180325162527.GA17492@light.dominikbrodowski.net
Cc: Ingo Molnar <mingo@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
Pull cgroup fixes from Tejun Heo:
"Two commits to fix the following subtle cgroup2 behavior bugs:
- cpu.max was rejecting config when it shouldn't
- thread mode enable was allowed when it shouldn't"
* 'for-4.16-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup: fix rule checking for threaded mode switching
sched, cgroup: Don't reject lower cpu.max on ancestors
The primary observation is that nohz enter/exit is always from the
current CPU, therefore NOHZ_TICK_STOPPED does not in fact need to be
an atomic.
Secondary is that we appear to have 2 nearly identical hooks in the
nohz enter code, set_cpu_sd_state_idle() and
nohz_balance_enter_idle(). Fold the whole set_cpu_sd_state thing into
nohz_balance_{enter,exit}_idle.
Removes an atomic op from both enter and exit paths.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Since we already iterate CPUs looking for work on NEWIDLE, use this
iteration to age the blocked load. If the domain for which this is
done completely spand the idle set, we can push the ILB based aging
forward.
Suggested-by: Brendan Jackman <brendan.jackman@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Split the NOHZ idle balancer into doing two separate actions:
- update blocked load statistic
- actually load-balance
Since the latter requires the former, ensure this happens. For now
always tag both bits at the same time.
Prepares for a future where we can toggle only the STATS bit.
Suggested-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Using atomic_t allows us to use the more flexible bitops provided
there. Also its smaller.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Make it easier to concatenate all the scheduler .c files for single-module
compilation.
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Do the following cleanups and simplifications:
- sched/sched.h already includes <asm/paravirt.h>, so no need to
include it in sched/core.c again.
- order the <linux/sched/*.h> headers alphabetically
- add all <linux/sched/*.h> headers to kernel/sched/sched.h
- remove all unnecessary includes from the .c files that
are already included in kernel/sched/sched.h.
Finally, make all scheduler .c files use a single common header:
#include "sched.h"
... which now contains a union of the relied upon headers.
This makes the various .c files easier to read and easier to handle.
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
A good number of small style inconsistencies have accumulated
in the scheduler core, so do a pass over them to harmonize
all these details:
- fix speling in comments,
- use curly braces for multi-line statements,
- remove unnecessary parentheses from integer literals,
- capitalize consistently,
- remove stray newlines,
- add comments where necessary,
- remove invalid/unnecessary comments,
- align structure definitions and other data types vertically,
- add missing newlines for increased readability,
- fix vertical tabulation where it's misaligned,
- harmonize preprocessor conditional block labeling
and vertical alignment,
- remove line-breaks where they uglify the code,
- add newline after local variable definitions,
No change in functionality:
md5:
1191fa0a890cfa8132156d2959d7e9e2 built-in.o.before.asm
1191fa0a890cfa8132156d2959d7e9e2 built-in.o.after.asm
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Now that the 1Hz tick is offloaded to workqueues, we can safely remove
the residual code that used to handle it locally.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Link: http://lkml.kernel.org/r/1519186649-3242-7-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
When a CPU runs in full dynticks mode, a 1Hz tick remains in order to
keep the scheduler stats alive. However this residual tick is a burden
for bare metal tasks that can't stand any interruption at all, or want
to minimize them.
The usual boot parameters "nohz_full=" or "isolcpus=nohz" will now
outsource these scheduler ticks to the global workqueue so that a
housekeeping CPU handles those remotely. The sched_class::task_tick()
implementations have been audited and look safe to be called remotely
as the target runqueue and its current task are passed in parameter
and don't seem to be accessed locally.
Note that in the case of using isolcpus, it's still up to the user to
affine the global workqueues to the housekeeping CPUs through
/sys/devices/virtual/workqueue/cpumask or domains isolation
"isolcpus=nohz,domain".
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Link: http://lkml.kernel.org/r/1519186649-3242-6-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Do that rename in order to normalize the hrtick namespace.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Link: http://lkml.kernel.org/r/1519186649-3242-2-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Mark noticed that he had sporadic "spinlock recursion" warnings from
the DEBUG_SPINLOCK code. Now rq->lock is special in that the owner
changes in the middle of a context switch.
It so happens that we fix up the lock.owner too late, @prev can run
(remotely) the moment prev->on_cpu is cleared, this then allows @prev
to again try and acquire this rq->lock and trigger this warning.
So we have to switch lock.owner before clearing prev->on_cpu.
Do this by moving the DEBUG_SPINLOCK annotation from after switch_to()
to before switch_to() and collect all lockdep annotations there into
prepare_lock_switch() to mirror the existing finish_lock_switch().
Debugged-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
While adding cgroup2 interface for the cpu controller, 0d5936344f
("sched: Implement interface for cgroup unified hierarchy") forgot to
update input validation and left it to reject cpu.max config if any
descendant has set a higher value.
cgroup2 officially supports delegation and a descendant must not be
able to restrict what its ancestors can configure. For absolute
limits such as cpu.max and memory.max, this means that the config at
each level should only act as the upper limit at that level and
shouldn't interfere with what other cgroups can configure.
This patch updates config validation on cgroup2 so that the cpu
controller follows the same convention.
Signed-off-by: Tejun Heo <tj@kernel.org>
Fixes: 0d5936344f ("sched: Implement interface for cgroup unified hierarchy")
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org # v4.15+
The select_idle_sibling() (SIS) rewrite in commit:
10e2f1acd0 ("sched/core: Rewrite and improve select_idle_siblings()")
... replaced a domain iteration with a search that broadly speaking
does a wrapped walk of the scheduler domain sharing a last-level-cache.
While this had a number of improvements, one consequence is that two tasks
that share a waker/wakee relationship push each other around a socket. Even
though two tasks may be active, all cores are evenly used. This is great from
a search perspective and spreads a load across individual cores, but it has
adverse consequences for cpufreq. As each CPU has relatively low utilisation,
cpufreq may decide the utilisation is too low to used a higher P-state and
overall computation throughput suffers.
While individual cpufreq and cpuidle drivers may compensate by artifically
boosting P-state (at c0) or avoiding lower C-states (during idle), it does
not help if hardware-based cpufreq (e.g. HWP) is used.
This patch tracks a recently used CPU based on what CPU a task was running
on when it last was a waker a CPU it was recently using when a task is a
wakee. During SIS, the recently used CPU is used as a target if it's still
allowed by the task and is idle.
The benefit may be non-obvious so consider an example of two tasks
communicating back and forth. Task A may be an application doing IO where
task B is a kworker or kthread like journald. Task A may issue IO, wake
B and B wakes up A on completion. With the existing scheme this may look
like the following (potentially different IDs if SMT is in use but similar
principal applies).
A (cpu 0) wake B (wakes on cpu 1)
B (cpu 1) wake A (wakes on cpu 2)
A (cpu 2) wake B (wakes on cpu 3)
etc.
A careful reader may wonder why CPU 0 was not idle when B wakes A the
first time and it's simply due to the fact that A can be rescheduled to
another CPU and the pattern is that prev == target when B tries to wakeup A
and the information about CPU 0 has been lost.
With this patch, the pattern is more likely to be:
A (cpu 0) wake B (wakes on cpu 1)
B (cpu 1) wake A (wakes on cpu 0)
A (cpu 0) wake B (wakes on cpu 1)
etc
i.e. two communicating casts are more likely to use just two cores instead
of all available cores sharing a LLC.
The most dramatic speedup was noticed on dbench using the XFS filesystem on
UMA as clients interact heavily with workqueues in that configuration. Note
that a similar speedup is not observed on ext4 as the wakeup pattern
is different:
4.15.0-rc9 4.15.0-rc9
waprev-v1 biasancestor-v1
Hmean 1 287.54 ( 0.00%) 817.01 ( 184.14%)
Hmean 2 1268.12 ( 0.00%) 1781.24 ( 40.46%)
Hmean 4 1739.68 ( 0.00%) 1594.47 ( -8.35%)
Hmean 8 2464.12 ( 0.00%) 2479.56 ( 0.63%)
Hmean 64 1455.57 ( 0.00%) 1434.68 ( -1.44%)
The results can be less dramatic on NUMA where automatic balancing interferes
with the test. It's also known that network benchmarks running on localhost
also benefit quite a bit from this patch (roughly 10% on netperf RR for UDP
and TCP depending on the machine). Hackbench also seens small improvements
(6-11% depending on machine and thread count). The facebook schbench was also
tested but in most cases showed little or no different to wakeup latencies.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20180130104555.4125-5-mgorman@techsingularity.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The whole of ttwu_stat() is guarded by a single schedstat_enabled(),
there is absolutely no point in then issuing another static_branch for
every single schedstat_inc() in there.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Provide core serializing membarrier command to support memory reclaim
by JIT.
Each architecture needs to explicitly opt into that support by
documenting in their architecture code how they provide the core
serializing instructions required when returning from the membarrier
IPI, and after the scheduler has updated the curr->mm pointer (before
going back to user-space). They should then select
ARCH_HAS_MEMBARRIER_SYNC_CORE to enable support for that command on
their architecture.
Architectures selecting this feature need to either document that
they issue core serializing instructions when returning to user-space,
or implement their architecture-specific sync_core_before_usermode().
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrea Parri <parri.andrea@gmail.com>
Cc: Andrew Hunter <ahh@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Avi Kivity <avi@scylladb.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Dave Watson <davejwatson@fb.com>
Cc: David Sehr <sehr@google.com>
Cc: Greg Hackmann <ghackmann@google.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Maged Michael <maged.michael@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-api@vger.kernel.org
Cc: linux-arch@vger.kernel.org
Link: http://lkml.kernel.org/r/20180129202020.8515-9-mathieu.desnoyers@efficios.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Document the membarrier requirement on having a full memory barrier in
__schedule() after coming from user-space, before storing to rq->curr.
It is provided by smp_mb__after_spinlock() in __schedule().
Document that membarrier requires a full barrier on transition from
kernel thread to userspace thread. We currently have an implicit barrier
from atomic_dec_and_test() in mmdrop() that ensures this.
The x86 switch_mm_irqs_off() full barrier is currently provided by many
cpumask update operations as well as write_cr3(). Document that
write_cr3() provides this barrier.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrea Parri <parri.andrea@gmail.com>
Cc: Andrew Hunter <ahh@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Avi Kivity <avi@scylladb.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Dave Watson <davejwatson@fb.com>
Cc: David Sehr <sehr@google.com>
Cc: Greg Hackmann <ghackmann@google.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Maged Michael <maged.michael@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-api@vger.kernel.org
Link: http://lkml.kernel.org/r/20180129202020.8515-4-mathieu.desnoyers@efficios.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Allow PowerPC to skip the full memory barrier in switch_mm(), and
only issue the barrier when scheduling into a task belonging to a
process that has registered to use expedited private.
Threads targeting the same VM but which belong to different thread
groups is a tricky case. It has a few consequences:
It turns out that we cannot rely on get_nr_threads(p) to count the
number of threads using a VM. We can use
(atomic_read(&mm->mm_users) == 1 && get_nr_threads(p) == 1)
instead to skip the synchronize_sched() for cases where the VM only has
a single user, and that user only has a single thread.
It also turns out that we cannot use for_each_thread() to set
thread flags in all threads using a VM, as it only iterates on the
thread group.
Therefore, test the membarrier state variable directly rather than
relying on thread flags. This means
membarrier_register_private_expedited() needs to set the
MEMBARRIER_STATE_PRIVATE_EXPEDITED flag, issue synchronize_sched(), and
only then set MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY which allows
private expedited membarrier commands to succeed.
membarrier_arch_switch_mm() now tests for the
MEMBARRIER_STATE_PRIVATE_EXPEDITED flag.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andrea Parri <parri.andrea@gmail.com>
Cc: Andrew Hunter <ahh@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Avi Kivity <avi@scylladb.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Dave Watson <davejwatson@fb.com>
Cc: David Sehr <sehr@google.com>
Cc: Greg Hackmann <ghackmann@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Maged Michael <maged.michael@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-api@vger.kernel.org
Cc: linux-arch@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Link: http://lkml.kernel.org/r/20180129202020.8515-3-mathieu.desnoyers@efficios.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Pull scheduler updates from Ingo Molnar:
"The main changes in this cycle were:
- Implement frequency/CPU invariance and OPP selection for
SCHED_DEADLINE (Juri Lelli)
- Tweak the task migration logic for better multi-tasking
workload scalability (Mel Gorman)
- Misc cleanups, fixes and improvements"
* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/deadline: Make bandwidth enforcement scale-invariant
sched/cpufreq: Move arch_scale_{freq,cpu}_capacity() outside of #ifdef CONFIG_SMP
sched/cpufreq: Remove arch_scale_freq_capacity()'s 'sd' parameter
sched/cpufreq: Always consider all CPUs when deciding next freq
sched/cpufreq: Split utilization signals
sched/cpufreq: Change the worker kthread to SCHED_DEADLINE
sched/deadline: Move CPU frequency selection triggering points
sched/cpufreq: Use the DEADLINE utilization signal
sched/deadline: Implement "runtime overrun signal" support
sched/fair: Only immediately migrate tasks due to interrupts if prev and target CPUs share cache
sched/fair: Correct obsolete comment about cpufreq_update_util()
sched/fair: Remove impossible condition from find_idlest_group_cpu()
sched/cpufreq: Don't pass flags to sugov_set_iowait_boost()
sched/cpufreq: Initialize sg_cpu->flags to 0
sched/fair: Consider RT/IRQ pressure in capacity_spare_wake()
sched/fair: Use 'unsigned long' for utilization, consistently
sched/core: Rework and clarify prepare_lock_switch()
sched/fair: Remove unused 'curr' parameter from wakeup_gran
sched/headers: Constify object_is_on_stack()
Pull RCU updates from Ingo Molnar:
"The main RCU changes in this cycle were:
- Updates to use cond_resched() instead of cond_resched_rcu_qs()
where feasible (currently everywhere except in kernel/rcu and in
kernel/torture.c). Also a couple of fixes to avoid sending IPIs to
offline CPUs.
- Updates to simplify RCU's dyntick-idle handling.
- Updates to remove almost all uses of smp_read_barrier_depends() and
read_barrier_depends().
- Torture-test updates.
- Miscellaneous fixes"
* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (72 commits)
torture: Save a line in stutter_wait(): while -> for
torture: Eliminate torture_runnable and perf_runnable
torture: Make stutter less vulnerable to compilers and races
locking/locktorture: Fix num reader/writer corner cases
locking/locktorture: Fix rwsem reader_delay
torture: Place all torture-test modules in one MAINTAINERS group
rcutorture/kvm-build.sh: Skip build directory check
rcutorture: Simplify functions.sh include path
rcutorture: Simplify logging
rcutorture/kvm-recheck-*: Improve result directory readability check
rcutorture/kvm.sh: Support execution from any directory
rcutorture/kvm.sh: Use consistent help text for --qemu-args
rcutorture/kvm.sh: Remove unused variable, `alldone`
rcutorture: Remove unused script, config2frag.sh
rcutorture/configinit: Fix build directory error message
rcutorture: Preempt RCU-preempt readers more vigorously
torture: Reduce #ifdefs for preempt_schedule()
rcu: Remove have_rcu_nocb_mask from tree_plugin.h
rcu: Add comment giving debug strategy for double call_rcu()
tracing, rcu: Hide trace event rcu_nocb_wake when not used
...
Before commit:
e33a9bba85 ("sched/core: move IO scheduling accounting from io_schedule_timeout() into scheduler")
delayacct_blkio_end() was called after context-switching into the task which
completed I/O.
This resulted in double counting: the task would account a delay both waiting
for I/O and for time spent in the runqueue.
With e33a9bba85, delayacct_blkio_end() is called by try_to_wake_up().
In ttwu, we have not yet context-switched. This is more correct, in that
the delay accounting ends when the I/O is complete.
But delayacct_blkio_end() relies on 'get_current()', and we have not yet
context-switched into the task whose I/O completed. This results in the
wrong task having its delay accounting statistics updated.
Instead of doing that, pass the task_struct being woken to delayacct_blkio_end(),
so that it can update the statistics of the correct task.
Signed-off-by: Josh Snyder <joshs@netflix.com>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Balbir Singh <bsingharora@gmail.com>
Cc: <stable@vger.kernel.org>
Cc: Brendan Gregg <bgregg@netflix.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-block@vger.kernel.org
Fixes: e33a9bba85 ("sched/core: move IO scheduling accounting from io_schedule_timeout() into scheduler")
Link: http://lkml.kernel.org/r/1513613712-571-1-git-send-email-joshs@netflix.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This patch adds the possibility of getting the delivery of a SIGXCPU
signal whenever there is a runtime overrun. The request is done through
the sched_flags field within the sched_attr structure.
Forward port of https://lkml.org/lkml/2009/10/16/170
Tested-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Juri Lelli <juri.lelli@gmail.com>
Signed-off-by: Claudio Scordino <claudio@evidence.eu.com>
Signed-off-by: Luca Abeni <luca.abeni@santannapisa.it>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tommaso Cucinotta <tommaso.cucinotta@sssup.it>
Link: http://lkml.kernel.org/r/1513077024-25461-1-git-send-email-claudio@evidence.eu.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The prepare_lock_switch() function has an unused parameter, and also the
function name was not descriptive. To improve readability and remove
the extra parameter, do the following changes:
* Move prepare_lock_switch() from kernel/sched/sched.h to
kernel/sched/core.c, rename it to prepare_task(), and remove the
unused parameter.
* Split the smp_store_release() out from finish_lock_switch() to a
function named finish_task.
* Comments ajdustments.
Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20171215140603.gxe5i2y6fg5ojfpp@smtp.gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Pull RCU updates from Paul E. McKenney:
- Updates to use cond_resched() instead of cond_resched_rcu_qs()
where feasible (currently everywhere except in kernel/rcu and
in kernel/torture.c). Also a couple of fixes to avoid sending
IPIs to offline CPUs.
- Updates to simplify RCU's dyntick-idle handling.
- Updates to remove almost all uses of smp_read_barrier_depends()
and read_barrier_depends().
- Miscellaneous fixes.
- Torture-test updates.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Fix the following kernel-doc warnings after code restructuring:
../kernel/sched/core.c:5113: warning: No description found for parameter 't'
../kernel/sched/core.c:5113: warning: Excess function parameter 'interval' description in 'sched_rr_get_interval'
get rid of set_fs()")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: abca5fc535 ("sched_rr_get_interval(): move compat to native,
Link: http://lkml.kernel.org/r/995c6ded-b32e-bbe4-d9f5-4d42d121aff1@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The rcutorture test suite occasionally provokes a splat due to invoking
resched_cpu() on an offline CPU:
WARNING: CPU: 2 PID: 8 at /home/paulmck/public_git/linux-rcu/arch/x86/kernel/smp.c:128 native_smp_send_reschedule+0x37/0x40
Modules linked in:
CPU: 2 PID: 8 Comm: rcu_preempt Not tainted 4.14.0-rc4+ #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
task: ffff902ede9daf00 task.stack: ffff96c50010c000
RIP: 0010:native_smp_send_reschedule+0x37/0x40
RSP: 0018:ffff96c50010fdb8 EFLAGS: 00010096
RAX: 000000000000002e RBX: ffff902edaab4680 RCX: 0000000000000003
RDX: 0000000080000003 RSI: 0000000000000000 RDI: 00000000ffffffff
RBP: ffff96c50010fdb8 R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000000 R11: 00000000299f36ae R12: 0000000000000001
R13: ffffffff9de64240 R14: 0000000000000001 R15: ffffffff9de64240
FS: 0000000000000000(0000) GS:ffff902edfc80000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000f7d4c642 CR3: 000000001e0e2000 CR4: 00000000000006e0
Call Trace:
resched_curr+0x8f/0x1c0
resched_cpu+0x2c/0x40
rcu_implicit_dynticks_qs+0x152/0x220
force_qs_rnp+0x147/0x1d0
? sync_rcu_exp_select_cpus+0x450/0x450
rcu_gp_kthread+0x5a9/0x950
kthread+0x142/0x180
? force_qs_rnp+0x1d0/0x1d0
? kthread_create_on_node+0x40/0x40
ret_from_fork+0x27/0x40
Code: 14 01 0f 92 c0 84 c0 74 14 48 8b 05 14 4f f4 00 be fd 00 00 00 ff 90 a0 00 00 00 5d c3 89 fe 48 c7 c7 38 89 ca 9d e8 e5 56 08 00 <0f> ff 5d c3 0f 1f 44 00 00 8b 05 52 9e 37 02 85 c0 75 38 55 48
---[ end trace 26df9e5df4bba4ac ]---
This splat cannot be generated by expedited grace periods because they
always invoke resched_cpu() on the current CPU, which is good because
expedited grace periods require that resched_cpu() unconditionally
succeed. However, other parts of RCU can tolerate resched_cpu() acting
as a no-op, at least as long as it doesn't happen too often.
This commit therefore makes resched_cpu() invoke resched_curr() only if
the CPU is either online or is the current CPU.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Pull compat and uaccess updates from Al Viro:
- {get,put}_compat_sigset() series
- assorted compat ioctl stuff
- more set_fs() elimination
- a few more timespec64 conversions
- several removals of pointless access_ok() in places where it was
followed only by non-__ variants of primitives
* 'misc.compat' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (24 commits)
coredump: call do_unlinkat directly instead of sys_unlink
fs: expose do_unlinkat for built-in callers
ext4: take handling of EXT4_IOC_GROUP_ADD into a helper, get rid of set_fs()
ipmi: get rid of pointless access_ok()
pi433: sanitize ioctl
cxlflash: get rid of pointless access_ok()
mtdchar: get rid of pointless access_ok()
r128: switch compat ioctls to drm_ioctl_kernel()
selection: get rid of field-by-field copyin
VT_RESIZEX: get rid of field-by-field copyin
i2c compat ioctls: move to ->compat_ioctl()
sched_rr_get_interval(): move compat to native, get rid of set_fs()
mips: switch to {get,put}_compat_sigset()
sparc: switch to {get,put}_compat_sigset()
s390: switch to {get,put}_compat_sigset()
ppc: switch to {get,put}_compat_sigset()
parisc: switch to {get,put}_compat_sigset()
get_compat_sigset()
get rid of {get,put}_compat_itimerspec()
io_getevents: Use timespec64 to represent timeouts
...
Pull cgroup updates from Tejun Heo:
"Cgroup2 cpu controller support is finally merged.
- Basic cpu statistics support to allow monitoring by default without
the CPU controller enabled.
- cgroup2 cpu controller support.
- /sys/kernel/cgroup files to help dealing with new / optional
features"
* 'for-4.15' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup: export list of cgroups v2 features using sysfs
cgroup: export list of delegatable control files using sysfs
cgroup: mark @cgrp __maybe_unused in cpu_stat_show()
MAINTAINERS: relocate cpuset.c
cgroup, sched: Move basic cpu stats from cgroup.stat to cpu.stat
sched: Implement interface for cgroup unified hierarchy
sched: Misc preps for cgroup unified hierarchy interface
sched/cputime: Add dummy cputime_adjust() implementation for CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
cgroup: statically initialize init_css_set->dfl_cgrp
cgroup: Implement cgroup2 basic CPU usage accounting
cpuacct: Introduce cgroup_account_cputime[_field]()
sched/cputime: Expose cputime_adjust()
Pull scheduler updates from Ingo Molnar:
"The main updates in this cycle were:
- Group balancing enhancements and cleanups (Brendan Jackman)
- Move CPU isolation related functionality into its separate
kernel/sched/isolation.c file, with related 'housekeeping_*()'
namespace and nomenclature et al. (Frederic Weisbecker)
- Improve the interactive/cpu-intense fairness calculation (Josef
Bacik)
- Improve the PELT code and related cleanups (Peter Zijlstra)
- Improve the logic of pick_next_task_fair() (Uladzislau Rezki)
- Improve the RT IPI based balancing logic (Steven Rostedt)
- Various micro-optimizations:
- better !CONFIG_SCHED_DEBUG optimizations (Patrick Bellasi)
- better idle loop (Cheng Jian)
- ... plus misc fixes, cleanups and updates"
* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (54 commits)
sched/core: Optimize sched_feat() for !CONFIG_SCHED_DEBUG builds
sched/sysctl: Fix attributes of some extern declarations
sched/isolation: Document isolcpus= boot parameter flags, mark it deprecated
sched/isolation: Add basic isolcpus flags
sched/isolation: Move isolcpus= handling to the housekeeping code
sched/isolation: Handle the nohz_full= parameter
sched/isolation: Introduce housekeeping flags
sched/isolation: Split out new CONFIG_CPU_ISOLATION=y config from CONFIG_NO_HZ_FULL
sched/isolation: Rename is_housekeeping_cpu() to housekeeping_cpu()
sched/isolation: Use its own static key
sched/isolation: Make the housekeeping cpumask private
sched/isolation: Provide a dynamic off-case to housekeeping_any_cpu()
sched/isolation, watchdog: Use housekeeping_cpumask() instead of ad-hoc version
sched/isolation: Move housekeeping related code to its own file
sched/idle: Micro-optimize the idle loop
sched/isolcpus: Fix "isolcpus=" boot parameter handling when !CONFIG_CPUMASK_OFFSTACK
x86/tsc: Append the 'tsc=' description for the 'tsc=unstable' boot parameter
sched/rt: Simplify the IPI based RT balancing logic
block/ioprio: Use a helper to check for RT prio
sched/rt: Add a helper to test for a RT task
...
When the kernel is compiled with !CONFIG_SCHED_DEBUG support, we expect that
all SCHED_FEAT are turned into compile time constants being propagated
to support compiler optimizations.
Specifically, we expect that code blocks like this:
if (sched_feat(FEATURE_NAME) [&& <other_conditions>]) {
/* FEATURE CODE */
}
are turned into dead-code in case FEATURE_NAME defaults to FALSE, and thus
being removed by the compiler from the finale image.
For this mechanism to properly work it's required for the compiler to
have full access, from each translation unit, to whatever is the value
defined by the sched_feat macro. This macro is defined as:
#define sched_feat(x) (sysctl_sched_features & (1UL << __SCHED_FEAT_##x))
and thus, the compiler can optimize that code only if the value of
sysctl_sched_features is visible within each translation unit.
Since:
029632fbb ("sched: Make separate sched*.c translation units")
the scheduler code has been split into separate translation units
however the definition of sysctl_sched_features is part of
kernel/sched/core.c while, for all the other scheduler modules, it is
visible only via kernel/sched/sched.h as an:
extern const_debug unsigned int sysctl_sched_features
Unfortunately, an extern reference does not allow the compiler to apply
constants propagation. Thus, on !CONFIG_SCHED_DEBUG kernel we still end up
with code to load a memory reference and (eventually) doing an unconditional
jump of a chunk of code.
This mechanism is unavoidable when sched_features can be turned on and off at
run-time. However, this is not the case for "production" kernels compiled with
!CONFIG_SCHED_DEBUG. In this case, sysctl_sched_features is just a constant value
which cannot be changed at run-time and thus memory loads and jumps can be
avoided altogether.
This patch fixes the case of !CONFIG_SCHED_DEBUG kernel by declaring a local version
of the sysctl_sched_features constant for each translation unit. This will
ultimately allow the compiler to perform constants propagation and dead-code
pruning.
Tests have been done, with !CONFIG_SCHED_DEBUG on a v4.14-rc8 with and without
the patch, by running 30 iterations of:
perf bench sched messaging --pipe --thread --group 4 --loop 50000
on a 40 cores Intel(R) Xeon(R) CPU E5-2690 v2 @ 3.00GHz using the
powersave governor to rule out variations due to frequency scaling.
Statistics on the reported completion time:
count mean std min 99% max
v4.14-rc8 30.0 15.7831 0.176032 15.442 16.01226 16.014
v4.14-rc8+patch 30.0 15.5033 0.189681 15.232 15.93938 15.962
... show a 1.8% speedup on average completion time and 0.5% speedup in the
99 percentile.
Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>
Signed-off-by: Chris Redpath <chris.redpath@arm.com>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Reviewed-by: Brendan Jackman <brendan.jackman@arm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Morten Rasmussen <morten.rasmussen@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Link: http://lkml.kernel.org/r/20171108184101.16006-1-patrick.bellasi@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
We want to centralize the isolation features, to be done by the housekeeping
subsystem and scheduler domain isolation is a significant part of it.
No intended behaviour change, we just reuse the housekeeping cpumask
and core code.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Link: http://lkml.kernel.org/r/1509072159-31808-11-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Before we implement isolcpus under housekeeping, we need the isolation
features to be more finegrained. For example some people want NOHZ_FULL
without the full scheduler isolation, others want full scheduler
isolation without NOHZ_FULL.
So let's cut all these isolation features piecewise, at the risk of
overcutting it right now. We can still merge some flags later if they
always make sense together.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Link: http://lkml.kernel.org/r/1509072159-31808-9-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Fit it into the housekeeping_*() namespace.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Link: http://lkml.kernel.org/r/1509072159-31808-7-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The housekeeping code is currently tied to the NOHZ code. As we are
planning to make housekeeping independent from it, start with moving
the relevant code to its own file.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Link: http://lkml.kernel.org/r/1509072159-31808-2-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The basic cpu stat is currently shown with "cpu." prefix in
cgroup.stat, and the same information is duplicated in cpu.stat when
cpu controller is enabled. This is ugly and not very scalable as we
want to expand the coverage of stat information which is always
available.
This patch makes cgroup core always create "cpu.stat" file and show
the basic cpu stat there and calls the cpu controller to show the
extra stats when enabled. This ensures that the same information
isn't presented in multiple places and makes future expansion of basic
stats easier.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
