linux-kernel - Re: [patch -mmotm] mm: invoke oom killer for __GFP

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Message-ID: <alpine.DEB.2.00.0905110138160.24726@chino.kir.corp.google.com>
Date:	Mon, 11 May 2009 01:40:50 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Minchan Kim <minchan.kim@...il.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Nick Piggin <npiggin@...e.de>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [patch -mmotm] mm: invoke oom killer for __GFP_NOFAIL

On Mon, 11 May 2009, Minchan Kim wrote:

> Hmm.. if __alloc_pages_may_oom fail to allocate free page due to order > PAGE_ALLOC_COSTRY_ORDER,
> 
> It will go to nopage label in __alloc_pages_slowpath.
> Then it will show the page allocation failure warning and will return. 
> Retrying depends on caller. 
> 

Correct.

> So, I think it won't loop forever. 
> Do I miss something ?
> 

__GFP_NOFAIL allocations shouldn't fail, that's the point of the gfp flag.  
So failing without attempting to free some memory is the wrong thing to 
do.

> In addition, the OOM killer can help for getting the high order pages ?
>  

Sure, if it selects a task that will free a lot of memory, which is it's 
goal.
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