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

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Date:	Mon, 11 May 2009 20:21:21 +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 6:12 PM, Minchan Kim <minchan.kim@...il.com> wrote:
> 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.

Now, I look over __out_of_memory.
For selecting better tasks in case of PAGE_ALLOC_COSTRY_ORDER, How
about increasing score of task which have VM_HUGETLB vma in badness ?

> --
> Kinds regards,
> Minchan Kim
>



-- 
Kinds regards,
Minchan Kim
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