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Subject: Re: [PATCH v3] cpuacct: VIRT_CPU_ACCOUNTING don't prevent percpu
 cputime count
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Ingo Molnar <mingo@elte.hu>, LKML <linux-kernel@vger.kernel.org>,
       Bharata B Rao <bharata@linux.vnet.ibm.com>,
       Balaji Rao <balajirrao@gmail.com>,
       Dhaval Giani <dhaval@linux.vnet.ibm.com>,
       KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
       Balbir Singh <balbir@linux.vnet.ibm.com>,
       Martin Schwidefsky <schwidefsky@de.ibm.com>
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Date: Sat, 09 May 2009 11:38:45 +0200
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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...

> @@ -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();
>