linux-kernel - Re: [patch 08/11 -mmotm] oom: invoke oom killer for __GFP

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Date:	Tue, 12 May 2009 20:36:38 +0900
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>, gregkh@...e.de,
	npiggin@...e.de, mel@....ul.ie, cl@...ux-foundation.org,
	dave@...ux.vnet.ibm.com, san@...roid.com, arve@...roid.com,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 08/11 -mmotm] oom: invoke oom killer for __GFP_NOFAIL

>> > Not sure it would help since the oom killer will be now be called for such
>> > an allocation and that dumps the stack (and will actually show the order
>> > and gfp flags as well).
>>
>> No, the intent of that warning is to find all call sites which use
>> __GFP_NOFAIL on order>0 so we can hunt down and eliminate them.
>>
>>
>> please review...
>
> Fully agreed, people should use banker's algorithm to guarantee
> progress, not create deadlocks with inf loops.
>
> Acked-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>

me too.

>
>> From: Andrew Morton <akpm@...ux-foundation.org>
>>
>> __GFP_NOFAIL is a bad fiction.  Allocations _can_ fail, and callers should
>> detect and suitably handle this (and not by lamely moving the infinite
>> loop up to the caller level either).
>>
>> Attempting to use __GFP_NOFAIL for a higher-order allocation is even
>> worse, so add a once-off runtime check for this to slap people around for
>> even thinking about trying it.
>>
>> Cc: David Rientjes <rientjes@...gle.com>
>> Cc: Mel Gorman <mel@....ul.ie>
>> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
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