Paul E. McKenney ef631b0ca0 rcu: Make hierarchical RCU less IPI-happy ... This patch fixes a hierarchical-RCU performance bug located by Anton Blanchard. The problem stems from a misguided attempt to provide a work-around for jiffies-counter failure. This work-around uses a per-CPU n_rcu_pending counter, which is incremented on each call to rcu_pending(), which in turn is called from each scheduling-clock interrupt. Each CPU then treats this counter as a surrogate for the jiffies counter, so that if the jiffies counter fails to advance, the per-CPU n_rcu_pending counter will cause RCU to invoke force_quiescent_state(), which in turn will (among other things) send resched IPIs to CPUs that have thus far failed to pass through an RCU quiescent state. Unfortunately, each CPU resets only its own counter after sending a batch of IPIs. This means that the other CPUs will also (needlessly) send -another- round of IPIs, for a full N-squared set of IPIs in the worst case every three scheduler-clock ticks until the grace period finally ends. It is not reasonable for a given CPU to reset each and every n_rcu_pending for all the other CPUs, so this patch instead simply disables the jiffies-counter "training wheels", thus eliminating the excessive IPIs. Note that the jiffies-counter IPIs do not have this problem due to the fact that the jiffies counter is global, so that the CPU sending the IPIs can easily reset things, thus preventing the other CPUs from sending redundant IPIs. Note also that the n_rcu_pending counter remains, as it will continue to be used for tracing. It may also see use to update the jiffies counter, should an appropriate kick-the-jiffies-counter API appear. Located-by: Anton Blanchard <anton@au1.ibm.com> Tested-by: Anton Blanchard <anton@au1.ibm.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: anton@samba.org Cc: akpm@linux-foundation.org Cc: dipankar@in.ibm.com Cc: manfred@colorfullife.com Cc: cl@linux-foundation.org Cc: josht@linux.vnet.ibm.com Cc: schamp@sgi.com Cc: niv@us.ibm.com Cc: dvhltc@us.ibm.com Cc: ego@in.ibm.com Cc: laijs@cn.fujitsu.com Cc: rostedt@goodmis.org Cc: peterz@infradead.org Cc: penberg@cs.helsinki.fi Cc: andi@firstfloor.org Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> LKML-Reference: <12396834793575-git-send-email-> Signed-off-by: Ingo Molnar <mingo@elte.hu>		2009-04-14 11:31:50 +02:00
..
irq	Merge branches 'core-fixes-for-linus', 'irq-fixes-for-linus' and 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip	2009-04-09 10:35:30 -07:00
power	PM/Hibernate: Wait for SCSI devices scan to complete during resume	2009-04-13 11:37:07 -07:00
time	Merge branch 'timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip	2009-03-26 16:05:42 -07:00
trace	tracing/filters: return proper error code when writing filter file	2009-04-12 11:59:29 +02:00
.gitignore
acct.c	[CVE-2009-0029] System call wrappers part 04	2009-01-14 14:15:19 +01:00
async.c	async: remove the temporary (2.6.29) "async is off by default" code	2009-03-28 13:05:30 -07:00
audit.c	Audit: remove spaces from audit_log_d_path	2009-04-05 13:49:04 -04:00
audit.h
audit_tree.c	audit: incorrect ref counting in audit tree tag_chunk	2009-04-05 13:48:26 -04:00
auditfilter.c	make the e->rule.xxx shorter in kernel auditfilter.c	2009-04-05 13:40:33 -04:00
auditsc.c	Audit: remove spaces from audit_log_d_path	2009-04-05 13:49:04 -04:00
backtracetest.c
bounds.c
capability.c	[CVE-2009-0029] System call wrappers part 04	2009-01-14 14:15:19 +01:00
cgroup.c	memcg: fix OOM killer under memcg	2009-04-02 19:04:55 -07:00
cgroup_debug.c	debug cgroup: remove unneeded cgroup_lock	2009-04-02 19:04:54 -07:00
cgroup_freezer.c
compat.c
configs.c
cpu.c	cpumask: use set_cpu_active in init/main.c	2009-03-30 22:05:12 +10:30
cpuset.c	cpusets: prevent PF_THREAD_BOUND tasks from attaching to non-root cpusets	2009-04-02 19:04:57 -07:00
cred-internals.h
cred.c
delayacct.c
dma-coherent.c	dma-coherent: Restore dma_alloc_from_coherent() large alloc fall back policy.	2009-01-21 18:51:53 +09:00
dma.c
exec_domain.c	Get rid of indirect include of fs_struct.h	2009-03-31 23:00:27 -04:00
exit.c	Merge branch 'irq/threaded' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip	2009-04-07 14:07:52 -07:00
extable.c	Merge branch 'tracing-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip	2009-04-05 11:04:19 -07:00
fork.c	Merge branches 'core-fixes-for-linus', 'irq-fixes-for-linus' and 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip	2009-04-09 10:35:30 -07:00
freezer.c
futex.c	futex: comment requeue key reference semantics	2009-04-02 23:39:53 +02:00
futex_compat.c
hrtimer.c	hrtimer: fix rq->lock inversion (again)	2009-03-31 14:52:52 +02:00
hung_task.c	softlockup: ensure the task has been switched out once	2009-02-11 11:04:16 +01:00
itimer.c	timers: split process wide cpu clocks/timers	2009-02-05 13:04:33 +01:00
kallsyms.c	Ksplice: Add functions for walking kallsyms symbols	2009-03-31 13:05:32 +10:30
Kconfig.freezer
Kconfig.hz
Kconfig.preempt
kexec.c	kexec: vmcoreinfo_data[] can become static	2009-04-02 19:05:04 -07:00
kfifo.c
kgdb.c
kmod.c	module: create a request_module_nowait()	2009-03-31 13:05:35 +10:30
kprobes.c	kprobes: support per-kprobe disabling	2009-04-07 08:31:08 -07:00
ksysfs.c
kthread.c	kthread: move sched-realeted initialization from kthreadd context	2009-04-09 09:50:37 +09:30
latencytop.c	sched, latencytop: incorporate review feedback from Andrew Morton	2009-02-11 10:18:04 +01:00
lockdep.c	Merge branch 'locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip	2009-04-06 13:37:30 -07:00
lockdep_internals.h	lockdep: get_user_chars() redo	2009-02-14 23:28:22 +01:00
lockdep_proc.c	lockstat: warn about disabled lock debugging	2009-02-14 23:28:28 +01:00
lockdep_states.h	lockdep: move state bit definitions around	2009-02-14 23:27:59 +01:00
Makefile	Merge branch 'linus' into core/softlockup	2009-04-07 11:15:40 +02:00
marker.c
module.c	async: Fix module loading async-work regression	2009-04-11 12:44:49 -07:00
mutex-debug.c	mutex: implement adaptive spinning	2009-01-14 18:09:02 +01:00
mutex-debug.h	mutex: implement adaptive spinning	2009-01-14 18:09:02 +01:00
mutex.c	mutex: have non-spinning mutexes on s390 by default	2009-04-09 19:28:24 +02:00
mutex.h	mutex: implement adaptive spinning	2009-01-14 18:09:02 +01:00
notifier.c
ns_cgroup.c	cgroups: relax ns_can_attach checks to allow attaching to grandchild cgroups	2009-04-02 19:04:53 -07:00
nsproxy.c
panic.c	lockdep: continue lock debugging despite some taints	2009-04-12 16:10:52 +02:00
params.c	param: fix charp parameters set via sysfs	2009-03-31 13:05:30 +10:30
pid.c	pids: refactor vnr/nr_ns helpers to make them safe	2009-04-02 19:05:02 -07:00
pid_namespace.c	signals: zap_pid_ns_process() should use force_sig()	2009-04-02 19:04:58 -07:00
pm_qos_params.c
posix-cpu-timers.c	Merge branch 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip	2009-04-09 10:37:28 -07:00
posix-timers.c	[CVE-2009-0029] System call wrappers part 05	2009-01-14 14:15:20 +01:00
printk.c	Merge branch 'printk-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip	2009-04-05 10:23:25 -07:00
profile.c	profiling: fix broken profiling regression	2009-02-10 00:50:37 +01:00
ptrace.c	ptrace: fix exit_ptrace() vs ptrace_traceme() race	2009-04-13 15:04:31 -07:00
rcuclassic.c	kmemtrace, rcu: fix linux/rcutree.h and linux/rcuclassic.h dependencies	2009-04-03 12:23:02 +02:00
rcupdate.c	rcu: rcu_barrier VS cpu_hotplug: Ensure callbacks in dead cpu are migrated to online cpu	2009-03-31 00:09:37 +02:00
rcupreempt.c	kmemtrace, rcu: fix rcupreempt.c data structure dependencies	2009-04-03 12:23:04 +02:00
rcupreempt_trace.c
rcutorture.c	cpumask: convert rcutorture.c	2009-03-30 22:05:16 +10:30
rcutree.c	rcu: Make hierarchical RCU less IPI-happy	2009-04-14 11:31:50 +02:00
rcutree.h	kmemtrace, rcu: fix rcu_tree_trace.c data structure dependencies	2009-04-03 12:23:03 +02:00
rcutree_trace.c	rcu: Make hierarchical RCU less IPI-happy	2009-04-14 11:31:50 +02:00
relay.c	Merge branch 'tracing-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip	2009-04-05 11:04:19 -07:00
res_counter.c
resource.c	resources: fix parameter name and kernel-doc	2009-01-15 16:39:38 -08:00
rtmutex-debug.c
rtmutex-debug.h
rtmutex-tester.c
rtmutex.c
rtmutex.h
rtmutex_common.h
rwsem.c
sched.c	Merge commit 'v2.6.30-rc1' into sched/urgent	2009-04-08 17:26:00 +02:00
sched_clock.c	Merge branch 'tracing/core-v2' into tracing-for-linus	2009-04-02 00:49:02 +02:00
sched_cpupri.c	sched_rt: don't allocate cpumask in fastpath	2009-04-01 13:24:51 +02:00
sched_cpupri.h	cpumask: remove cpumask_t from core	2009-03-30 22:05:17 +10:30
sched_debug.c	sched: remove unused fields from struct rq	2009-03-24 23:16:51 +01:00
sched_fair.c	Merge branch 'sched/urgent'; commit 'v2.6.29-rc5' into sched/core	2009-02-15 21:15:16 +01:00
sched_features.h	Merge branch 'locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip	2009-03-30 17:17:35 -07:00
sched_idletask.c
sched_rt.c	Merge commit 'v2.6.30-rc1' into sched/urgent	2009-04-08 17:26:00 +02:00
sched_stats.h	sched: remove unused fields from struct rq	2009-03-24 23:16:51 +01:00
seccomp.c	x86-64: seccomp: fix 32/64 syscall hole	2009-03-02 15:41:30 -08:00
semaphore.c
signal.c	signals: SI_USER: Masquerade si_pid when crossing pid ns boundary	2009-04-02 19:04:58 -07:00
slow-work.c	Document the slow work thread pool	2009-04-03 16:42:35 +01:00
smp.c	generic-ipi: eliminate WARN_ON()s during oops/panic	2009-03-13 10:47:34 +01:00
softirq.c	Merge branch 'locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip	2009-04-06 13:37:30 -07:00
softlockup.c	softlockup: decouple hung tasks check from softlockup detection	2009-01-16 14:06:04 +01:00
spinlock.c	Allow rwlocks to re-enable interrupts	2009-04-02 19:05:11 -07:00
srcu.c
stacktrace.c
stop_machine.c	cpumask: remove cpumask_t from core	2009-03-30 22:05:17 +10:30
sys.c	kernel/sys.c: clean up sys_shutdown exit path	2009-04-13 15:04:32 -07:00
sys_ni.c	[CVE-2009-0029] Make sys_syslog a conditional system call	2009-01-14 14:15:16 +01:00
sysctl.c	mm: move the scan_unevictable_pages sysctl to the vm table	2009-04-13 15:04:28 -07:00
sysctl_check.c	net: add ARP notify option for devices	2009-02-01 01:04:33 -08:00
taskstats.c
test_kprobes.c
time.c	[CVE-2009-0029] System call wrappers part 01	2009-01-14 14:15:18 +01:00
timeconst.pl
timer.c	Merge branches 'core-fixes-for-linus', 'irq-fixes-for-linus' and 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip	2009-04-09 10:35:30 -07:00
tracepoint.c	tracepoints: dont update zero-sized tracepoint sections	2009-03-18 19:55:00 +01:00
tsacct.c	Fix fixpoint divide exception in acct_update_integrals	2009-03-09 08:13:35 -07:00
uid16.c	[CVE-2009-0029] System call wrappers part 19	2009-01-14 14:15:26 +01:00
up.c	smp_call_function_single(): be slightly less stupid, fix #2	2009-01-12 16:04:37 +01:00
user.c	Merge branch 'master' into next	2009-03-24 10:52:46 +11:00
user_namespace.c	Fix recursive lock in free_uid()/free_user_ns()	2009-02-27 16:26:21 -08:00
utsname.c
utsname_sysctl.c	proc_sysctl: use CONFIG_PROC_SYSCTL around ipc and utsname proc_handlers	2009-04-02 19:05:01 -07:00
wait.c	wait: prevent exclusive waiter starvation	2009-02-05 12:56:48 -08:00
workqueue.c	work_on_cpu(): rewrite it to create a kernel thread on demand	2009-04-09 09:50:37 +09:30