Date: Wed, 17 Oct 2012 15:32:29 -0400
From: Dave Jones <davej@redhat.com>
To: David Rientjes <rientjes@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        KOSAKI Motohiro <kosaki.motohiro@gmail.com>, bhutchings@solarflare.com,
        Konstantin Khlebnikov <khlebnikov@openvz.org>,
        Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
        Hugh Dickins <hughd@google.com>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [patch for-3.7] mm, mempolicy: fix printing stack contents in
 numa_maps
Message-ID: <20121017193229.GC16805@redhat.com>
Mail-Followup-To: Dave Jones <davej@redhat.com>,
	David Rientjes <rientjes@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@gmail.com>,
	bhutchings@solarflare.com,
	Konstantin Khlebnikov <khlebnikov@openvz.org>,
	Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
	Hugh Dickins <hughd@google.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org
References: <alpine.DEB.2.00.1210152055150.5400@chino.kir.corp.google.com>
 <CAHGf_=rLjQbtWQLDcbsaq5=zcZgjdveaOVdGtBgBwZFt78py4Q@mail.gmail.com>
 <alpine.DEB.2.00.1210152306320.9480@chino.kir.corp.google.com>
 <CAHGf_=pemT6rcbu=dBVSJE7GuGWwVFP+Wn-mwkcsZ_gBGfaOsg@mail.gmail.com>
 <alpine.DEB.2.00.1210161657220.14014@chino.kir.corp.google.com>
 <alpine.DEB.2.00.1210161714110.17278@chino.kir.corp.google.com>
 <20121017040515.GA13505@redhat.com>
 <alpine.DEB.2.00.1210162222100.26279@chino.kir.corp.google.com>
 <20121017181413.GA16805@redhat.com>
 <alpine.DEB.2.00.1210171219010.28214@chino.kir.corp.google.com>
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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@bitcrush: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@bitcrush: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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