linux-kernel - Re: [patch for-3.7] mm, mempolicy: fix printing stack contents in numa

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Message-ID: <20121017193229.GC16805@redhat.com>
Date:	Wed, 17 Oct 2012 15:32:29 -0400
From:	Dave Jones <davej@...hat.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	bhutchings@...arflare.com,
	Konstantin Khlebnikov <khlebnikov@...nvz.org>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Hugh Dickins <hughd@...gle.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch for-3.7] mm, mempolicy: fix printing stack contents in
 numa_maps

On Wed, Oct 17, 2012 at 12:21:10PM -0700, David Rientjes wrote:
 > On Wed, 17 Oct 2012, Dave Jones wrote:
 > 
 > > On Tue, Oct 16, 2012 at 10:24:32PM -0700, David Rientjes wrote:
 > >  > On Wed, 17 Oct 2012, Dave Jones wrote:
 > >  > 
 > >  > > BUG: sleeping function called from invalid context at kernel/mutex.c:269
 > >  > 
 > >  > Hmm, looks like we need to change the refcount semantics entirely.  We'll 
 > >  > need to make get_vma_policy() always take a reference and then drop it 
 > >  > accordingly.  This work sif get_vma_policy() can grab a reference while 
 > >  > holding task_lock() for the task policy fallback case.
 > >  > 
 > >  > Comments on this approach?
 > > 
 > > Seems to be surviving my testing at least..
 > > 
 > 
 > Sounds good.  Is it possible to verify that policy_cache isn't getting 
 > larger than normal in /proc/slabinfo, i.e. when all processes with a 
 > task mempolicy or shared vma policy have exited, are there still a 
 > significant number of active objects?

Killing the fuzzer caused it to drop dramatically.

Before:
(15:29:59:davej@...crush:trinity[master])$ sudo cat /proc/slabinfo  | grep policy
shared_policy_node   2931   2967    376   43    4 : tunables    0    0    0 : slabdata     69     69      0
numa_policy         2971   6545    464   35    4 : tunables    0    0    0 : slabdata    187    187      0

After:
(15:30:16:davej@...crush:trinity[master])$ sudo cat /proc/slabinfo  | grep policy
shared_policy_node      0    215    376   43    4 : tunables    0    0    0 : slabdata      5      5      0
numa_policy           15    175    464   35    4 : tunables    0    0    0 : slabdata      5      5      0


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