Messages in this thread Patch in this message | | | Date | Mon, 11 May 2009 12:36:29 GMT | From | tip-bot for KOSAKI Motohiro <> | Subject | [tip:sched/core] sched: cpuacct: Use bigger percpu counter batch values for stats counters |
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Commit-ID: 50fbed3bb72cbe38a665512771a91a96d028de46 Gitweb: http://git.kernel.org/tip/50fbed3bb72cbe38a665512771a91a96d028de46 Author: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> AuthorDate: Sat, 9 May 2009 19:14:58 +0900 Committer: Ingo Molnar <mingo@elte.hu> CommitDate: Mon, 11 May 2009 14:32:57 +0200
sched: cpuacct: Use bigger percpu counter batch values for stats counters
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.
v5: - move cpuacct_batch initialization into sched_init()
v4: - rewrite patch description (thanks Bharata!) - append read_mostly to cpuacct_batch - cpuacct_batch is initialized by sched_init_debug()
v3: - revert using percpu_counter_sum()
v2: - use percpu_counter_sum() instead percpu_counter_read()
Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Balaji Rao <balajirrao@gmail.com> Cc: Dhaval Giani <dhaval@linux.vnet.ibm.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Balbir Singh <balbir@linux.vnet.ibm.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> LKML-Reference: <20090509191430.3AD5.A69D9226@jp.fujitsu.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
--- kernel/sched.c | 7 ++++++- 1 files changed, 6 insertions(+), 1 deletions(-)
diff --git a/kernel/sched.c b/kernel/sched.c index 8908d19..873bc3b 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -872,6 +872,8 @@ static __read_mostly int scheduler_running; */ 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; @@ -9171,6 +9173,8 @@ void __init sched_init(void) */ current->sched_class = &fair_sched_class; + cpuacct_batch = jiffies_to_cputime(percpu_counter_batch); + /* Allocate the nohz_cpu_mask if CONFIG_CPUMASK_OFFSTACK */ alloc_bootmem_cpumask_var(&nohz_cpu_mask); #ifdef CONFIG_SMP @@ -10354,7 +10358,8 @@ static void cpuacct_update_stats(struct task_struct *tsk, 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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