linux-kernel - Re: [bug] SLUB + mm/slab.c boot crash in -rc9

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Message-ID: <48051DB1.8080102@sgi.com>
Date:	Tue, 15 Apr 2008 14:27:13 -0700
From:	Mike Travis <travis@....com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Christoph Lameter <clameter@....com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	linux-kernel@...r.kernel.org, Mel Gorman <mel@....ul.ie>,
	Nick Piggin <npiggin@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Yinghai.Lu@....com,
	apw@...dowen.org,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [bug] SLUB + mm/slab.c boot crash in -rc9

Ingo Molnar wrote:
> * Christoph Lameter <clameter@....com> wrote:
> 
>> On Tue, 15 Apr 2008, Ingo Molnar wrote:
>>
>>> and the bug pattern seems to be memory corruption - not memory 
>>> exhaustion.
>> SLUB does not do a memory allocation where it fails here but simply 
>> accesses per cpu information that is expected to be already zeroed.
>>
>>> i.e. we allocated RAM but it got corrupted after allocation.
>> In some situations we are screwing up the per cpu data handling on 32 
>> bit x86? Adding Mike. This looks like the per cpu area overlaps with 
>> something else?
> 
> yep, that was my other theory - and i doubled CONFIG_NR_CPUS to reduce 
> that chance.
> 
> in hindsight ... that wont save us from any overlap, right?
> 
> what's the best way to artificially increase the size of the allocated 
> per cpu area? (say double it)
> 
> 	Ingo

I don't know that there is a boot option.  If modules are defined it
adds an extra 8k.  The size is defined in include/linux/percpu.h 
(PERCPU_ENOUGH_ROOM).

Otherwise define a really large per_cpu variable...?

-Mike
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