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

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Date:	Fri, 29 Apr 2011 22:14:50 +0200
From:	Bruno Prémont <bonbons@...ux-vserver.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	john stultz <johnstul@...ibm.com>, 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 Fri, 29 April 2011 Thomas Gleixner wrote:
> On Fri, 29 Apr 2011, Bruno Prémont wrote:
> > On Fri, 29 April 2011 Thomas Gleixner wrote:
> > > On Thu, 28 Apr 2011, john stultz wrote:
> > > > On Thu, 2011-04-28 at 23:04 +0200, Thomas Gleixner wrote:
> > > > > /me suspects hrtimer changes to be the real culprit.
> > > > 
> > > > I'm not seeing anything on right off, but it does smell like
> > > > e06383db9ec591696a06654257474b85bac1f8cb would be where such an issue
> > > > would crop up.
> > > > 
> > > > Bruno, could you try checking out e06383db9ec, confirming it still
> > > > occurs (and then maybe seeing if it goes away at e06383db9ec^1)?
> > > > 
> > > > I'll keep digging in the meantime.
> > > 
> > > I found the bug already. The problem is that sched_init() calls
> > > init_rt_bandwidth() which calls hrtimer_init() _BEFORE_
> > > hrtimers_init() is called.
> > > 
> > > That was unnoticed so far as the CLOCK id to hrtimer base conversion
> > > was hardcoded. Now we use a table which is set up at hrtimers_init(),
> > > so the bandwith hrtimer ends up on CLOCK_REALTIME because the table is
> > > in the bss.
> > > 
> > > The patch below fixes this, by providing the table statically rather
> > > than runtime initialized. Though that whole ordering wants to be
> > > revisited.
> > 
> > Works here as well (applied alone), /proc/$(pidof rcu_kthread)/sched shows
> > total runtime continuing to increase beyond 950 and slubs continue being
> > released!
> 
> Does the CPU time show up in top/ps as well now ?

Yes, it does (currently at 0:09 in ps for 9336.075 in
/proc/$(pidof rcu_kthread)/sched)

Thanks,
Bruno
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