linux-kernel - Re: [patch 13/15] sched: add exports tracking cfs bandwidth control statistics

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Date:	Wed, 11 May 2011 02:09:05 -0700
From:	Paul Turner <pjt@...gle.com>
To:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Bharata B Rao <bharata@...ux.vnet.ibm.com>,
	Dhaval Giani <dhaval.giani@...il.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Pavel Emelyanov <xemul@...nvz.org>,
	Nikhil Rao <ncrao@...gle.com>
Subject: Re: [patch 13/15] sched: add exports tracking cfs bandwidth control statistics

On Wed, May 11, 2011 at 12:56 AM, Hidetoshi Seto
<seto.hidetoshi@...fujitsu.com> wrote:
> Oops, I found an issue here.
>
> (2011/05/03 18:28), Paul Turner wrote:
>> @@ -1628,6 +1631,12 @@ retry:
>>               raw_spin_unlock(&cfs_b->lock);
>>               goto retry;
>>       }
>> +
>> +     /* update throttled stats */
>> +     cfs_b->nr_periods += overrun;
>> +     if (throttled)
>> +             cfs_b->nr_throttled += overrun;
>> +
>>       cfs_b->runtime = runtime;
>>       cfs_b->idle = idle;
>>  out_unlock:
>
> Quoting from patch 09/15:
>
> +       if (!throttled || quota == RUNTIME_INF)
> +               goto out;
> +       idle = 0;
> +
> +retry:
> +       runtime = distribute_cfs_runtime(cfs_b, runtime, runtime_expires);
> +
> +       raw_spin_lock(&cfs_b->lock);
> +       /* new new bandwidth may have been set */
> +       if (unlikely(runtime_expires != cfs_b->runtime_expires))
> +               goto out_unlock;
> +       /*
> +        * make sure no-one was throttled while we were handing out the new
> +        * runtime.
> +        */
> +       if (runtime > 0 && !list_empty(&cfs_b->throttled_cfs_rq)) {
> +               raw_spin_unlock(&cfs_b->lock);
> +               goto retry;
> +       }
> +       cfs_b->runtime = runtime;
> +       cfs_b->idle = idle;
> +out_unlock:
> +       raw_spin_unlock(&cfs_b->lock);
> +out:
>
> Since we skip distributing runtime (by "goto out") when !throttled,
> the new block inserted by this patch is passed only when throttled.
> So I see that nr_periods and nr_throttled look the same.
>
> Maybe we should move this block up like followings.
>

Yes, makes sense, incorporated -- thanks!

> Thanks,
> H.Seto
>
> ---
> --- a/kernel/sched_fair.c
> +++ b/kernel/sched_fair.c
> @@ -1620,6 +1620,12 @@ static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
>                idle = cfs_b->idle;
>                cfs_b->idle = 1;
>        }
> +
> +       /* update throttled stats */
> +       cfs_b->nr_periods += overrun;
> +       if (throttled)
> +               cfs_b->nr_throttled += overrun;
> +
>        raw_spin_unlock(&cfs_b->lock);
>
>        if (!throttled || quota == RUNTIME_INF)
> @@ -1642,11 +1648,6 @@ retry:
>                goto retry;
>        }
>
> -       /* update throttled stats */
> -       cfs_b->nr_periods += overrun;
> -       if (throttled)
> -               cfs_b->nr_throttled += overrun;
> -
>        cfs_b->runtime = runtime;
>        cfs_b->idle = idle;
>  out_unlock:
>
>
>
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