Messages in this thread | | | Date | Thu, 30 Apr 2009 11:48:06 +0530 | From | Balbir Singh <> | Subject | Re: [PATCH v2] cpuacct: VIRT_CPU_ACCOUNTING don't prevent percpu cputime count |
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* KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> [2009-04-30 15:11:15]:
> > Changelog: > since v1 > - use percpu_counter_sum() instead percpu_counter_read() > > > ------------------------------------- > Subject: [PATCH v2] cpuacct: VIRT_CPU_ACCOUNTING don't prevent percpu cputime count > > cpuacct_update_stats() is called at every tick updating. and it use percpu_counter > for avoiding performance degression. > > For archs which define VIRT_CPU_ACCOUNTING, every tick would result > in >1000 units of cputime updates and since this is much much greater > than percpu_batch_counter, we end up taking spinlock on every tick. > > This patch change batch rule. now, any cpu can store "percpu_counter_bach * jiffies" > cputime in per-cpu cache. > it mean this patch don't have behavior change if VIRT_CPU_ACCOUNTING=n. > > Cc: Bharata B Rao <bharata@linux.vnet.ibm.com> > 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: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> > --- > kernel/sched.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > Index: b/kernel/sched.c > =================================================================== > --- a/kernel/sched.c 2009-04-30 11:37:47.000000000 +0900 > +++ b/kernel/sched.c 2009-04-30 14:17:00.000000000 +0900 > @@ -10221,6 +10221,7 @@ struct cpuacct { > }; > > struct cgroup_subsys cpuacct_subsys; > +static s32 cpuacct_batch; > > /* return cpu accounting group corresponding to this container */ > static inline struct cpuacct *cgroup_ca(struct cgroup *cgrp) > @@ -10250,6 +10251,9 @@ static struct cgroup_subsys_state *cpuac > if (!ca->cpuusage) > goto out_free_ca; > > + if (!cpuacct_batch) > + cpuacct_batch = jiffies_to_cputime(percpu_counter_batch); > + > for (i = 0; i < CPUACCT_STAT_NSTATS; i++) > if (percpu_counter_init(&ca->cpustat[i], 0)) > goto out_free_counters; > @@ -10376,7 +10380,7 @@ static int cpuacct_stats_show(struct cgr > int i; > > for (i = 0; i < CPUACCT_STAT_NSTATS; i++) { > - s64 val = percpu_counter_read(&ca->cpustat[i]); > + s64 val = percpu_counter_sum(&ca->cpustat[i]); > val = cputime64_to_clock_t(val); > cb->fill(cb, cpuacct_stat_desc[i], val); > } > @@ -10446,7 +10450,7 @@ 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(); > >
What do the test results look like with this? I'll see if I can find some time to test this patch. On a patch read level this seems much better to me, Peter?
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
-- Balbir
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