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

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Message-ID: <28c262360905110212j9867b79wd8d90b16f6f196be@mail.gmail.com>
Date:	Mon, 11 May 2009 18:12:46 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	David Rientjes <rientjes@...gle.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, May 11, 2009 at 5:40 PM, David Rientjes <rientjes@...gle.com> wrote:
> 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.

Thanks for quick reply.
I was confused by your description.
I thought you suggested we have to prevent loop forever.

>
>> 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.
>

How do we know any task have a lot of memory ?
If we select wrong task and kill one ?

I have a concern about innocent task.

-- 
Kinds regards,
Minchan Kim
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