Messages in this thread Patch in this message | | | From | KOSAKI Motohiro <> | Subject | Re: [PATCH v3] cpuacct: VIRT_CPU_ACCOUNTING don't prevent percpu cputime count | Date | Sat, 9 May 2009 19:14:58 +0900 (JST) |
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> > On Sat, 2009-05-09 at 18:26 +0900, KOSAKI Motohiro wrote: > > > > > > Index: b/kernel/sched.c > > > =================================================================== > > > --- a/kernel/sched.c 2009-05-09 16:48:08.000000000 +0900 > > > +++ b/kernel/sched.c 2009-05-09 18:16:00.000000000 +0900 > > > @@ -824,8 +824,12 @@ static struct file_operations sched_feat > > > .release = single_release, > > > }; > > > > > > +static __read_mostly s32 cpuacct_batch; > > > + > > > static __init int sched_init_debug(void) > > > { > > > + cpuacct_batch = jiffies_to_cputime(percpu_counter_batch); > > > + > > > debugfs_create_file("sched_features", 0644, NULL, NULL, > > > &sched_feat_fops); > > > > I'm pretty user you can select cpu accounting without SCHED_DEBUG... > > Grr, yes, it's idiot ;) > I'll fix it soon.
Done.
Changelog: since V4 - move cpuacct_batch initialization into sched_init()
since V3 - rewirte patch description (thanks Bharata!) - append read_mostly to cpuacct_batch - cpuacct_batch is initialized by sched_init_debug()
since v2 - revert using percpu_counter_sum()
since v1 - use percpu_counter_sum() instead percpu_counter_read()
--------------------------------------------------------- Subject: [PATCH v5] cpuacct: Use bigger percpu counter batch values for stats counters on archs that have VIRT_CPU_ACCOUNTING=y
percpu counters used to accumulate statistics in cpuacct controller use the default batch value [max(2*nr_cpus, 32)] which can be too small for archs that define VIRT_CPU_ACCOUNTING. In such archs, a tick could result in cputime updates in the range of thousands. As a result, cpuacct_update_stats() would end up acquiring the percpu counter spinlock on every tick which is not good for performance.
Let those architectures to have a bigger batch threshold so that percpu counter spinlock isn't taken on every tick. This change doesn't affect the archs which don't define VIRT_CPU_ACCOUNTING and they continue to have the default percpu counter batch value.
Cc: Balaji Rao <balajirrao@gmail.com> Cc: Dhaval Giani <dhaval@linux.vnet.ibm.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Balbir Singh <balbir@linux.vnet.ibm.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> --- kernel/sched.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
Index: b/kernel/sched.c =================================================================== --- a/kernel/sched.c 2009-05-09 16:48:08.000000000 +0900 +++ b/kernel/sched.c 2009-05-09 18:57:35.000000000 +0900 @@ -870,6 +870,8 @@ static __read_mostly int scheduler_runni */ int sysctl_sched_rt_runtime = 950000; +static __read_mostly s32 cpuacct_batch; + static inline u64 global_rt_period(void) { return (u64)sysctl_sched_rt_period * NSEC_PER_USEC; @@ -9284,6 +9286,8 @@ void __init sched_init(void) perf_counter_init(); + cpuacct_batch = jiffies_to_cputime(percpu_counter_batch); + scheduler_running = 1; } @@ -10457,7 +10461,8 @@ static void cpuacct_update_stats(struct ca = task_ca(tsk); do { - percpu_counter_add(&ca->cpustat[idx], val); + __percpu_counter_add(&ca->cpustat[idx], val, cpuacct_batch); + ca = ca->parent; } while (ca); rcu_read_unlock();
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