linux-kernel - Re: 2.6.39-rc4+: Kernel leaking memory during FS scanning, regression?

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Message-ID: <20110428222301.0b745a0a@neptune.home>
Date:	Thu, 28 Apr 2011 22:23:01 +0200
From:	Bruno Prémont <bonbons@...ux-vserver.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	sedat.dilek@...il.com, Mike Galbraith <efault@....de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Mike Frysinger <vapier.adi@...il.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
	linux-fsdevel@...r.kernel.org,
	"Paul E. McKenney" <paul.mckenney@...aro.org>,
	Pekka Enberg <penberg@...nel.org>
Subject: Re: 2.6.39-rc4+: Kernel leaking memory during FS scanning,
 regression?

On Thu, 28 April 2011 Thomas Gleixner <tglx@...utronix.de> wrote:
> On Thu, 28 Apr 2011, Sedat Dilek wrote:
> > On Thu, Apr 28, 2011 at 3:30 PM, Mike Galbraith <efault@....de> wrote:
> > rt_rq[0]:
> >   .rt_nr_running                 : 0
> >   .rt_throttled                  : 0
> 
> >   .rt_time                       : 888.893877
> 
> >   .rt_time                       : 950.005460
> 
> So rt_time is constantly accumulated, but never decreased. The
> decrease happens in the timer callback. Looks like the timer is not
> running for whatever reason.
> 
> Can you add the following patch as well ?
> 
> Thanks,
> 
> 	tglx
> 
> --- linux-2.6.orig/kernel/sched.c
> +++ linux-2.6/kernel/sched.c
> @@ -172,7 +172,7 @@ static enum hrtimer_restart sched_rt_per
>  		idle = do_sched_rt_period_timer(rt_b, overrun);
>  	}
>  
> -	return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
> +	return HRTIMER_RESTART;

This doesn't help here.
Be it applied on top of the others, full diff attached
or applied alone (with throttling printk).

Could it be that NO_HZ=y has some importance in this matter?


Extended throttling printk (Linus asked what exact values were looking
like):
[  401.000119] sched: RT throttling activated 950012539 > 950000000


Equivalent to what Sedat sees (/proc/sched_debug):
rt_rq[0]:
  .rt_nr_running                 : 2
  .rt_throttled                  : 1
  .rt_time                       : 950.012539
  .rt_runtime                    : 950.000000


/proc/$(pidof rcu_kthread)/sched captured at regular intervals:
Thu Apr 28 21:33:41 CEST 2011
rcu_kthread (6, #threads: 1)
---------------------------------------------------------
se.exec_start                      :             0.000000
se.vruntime                        :             0.000703
se.sum_exec_runtime                :           903.067982
nr_switches                        :                23752
nr_voluntary_switches              :                23751
nr_involuntary_switches            :                    1
se.load.weight                     :                 1024
policy                             :                    1
prio                               :                   98
clock-delta                        :                  912
Thu Apr 28 21:34:11 CEST 2011
rcu_kthread (6, #threads: 1)
---------------------------------------------------------
se.exec_start                      :             0.000000
se.vruntime                        :             0.000703
se.sum_exec_runtime                :           974.899495
nr_switches                        :                25721
nr_voluntary_switches              :                25720
nr_involuntary_switches            :                    1
se.load.weight                     :                 1024
policy                             :                    1
prio                               :                   98
clock-delta                        :                 1098
Thu Apr 28 21:34:41 CEST 2011
rcu_kthread (6, #threads: 1)
---------------------------------------------------------
se.exec_start                      :             0.000000
se.vruntime                        :             0.000703
se.sum_exec_runtime                :           974.899495
nr_switches                        :                25721
nr_voluntary_switches              :                25720
nr_involuntary_switches            :                    1
se.load.weight                     :                 1024
policy                             :                    1
prio                               :                   98
clock-delta                        :                 1126
Thu Apr 28 21:35:11 CEST 2011
rcu_kthread (6, #threads: 1)



>  }
>  
>  static

View attachment "sched_rt.diff" of type "text/x-patch" (2052 bytes)