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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: mgorman@suse.de
Cc: minchan.kim@gmail.com, abarry@cray.com,
	akpm@linux-foundation.org, linux-mm@kvack.org, riel@redhat.com,
	hannes@cmpxchg.org, linux-kernel@vger.kernel.org
Subject: Re: Unending loop in __alloc_pages_slowpath following OOM-kill; rfc: patch.
Date: Tue, 24 May 2011 18:40:31 +0900	[thread overview]
Message-ID: <4DDB7D0F.3060204@jp.fujitsu.com> (raw)
In-Reply-To: <20110524091611.GD5279@suse.de>

(2011/05/24 18:16), Mel Gorman wrote:
> On Tue, May 24, 2011 at 06:05:59PM +0900, KOSAKI Motohiro wrote:
>>>>> Why?
>>>>
>>>> Otherwise, we don't have good PCP dropping trigger. Big machine might have
>>>> big pcp cache.
>>>>
>>>
>>> Big machines also have a large cost for sending IPIs.
>>
>> Yes. But it's only matter if IPIs are frequently happen.
>> But, drain_all_pages() is NOT only IPI source. some vmscan function (e.g.
>> try_to_umap) makes a lot of IPIs.
>>
>> Then, it's _relatively_ not costly. I have a question. Do you compare which
>> operation and drain_all_pages()? IOW, your "costly" mean which scenario suspect?
>>
> 
> I am concerned that if the machine gets into trouble and we are failing
> to reclaim that sending more IPIs is not going to help any. There is no
> evidence at the moment that sending extra IPIs here will help anything.

In old days, we always call drain_all_pages() if did_some_progress!=0. But
current kernel only call it when get_page_from_freelist() fail. So,
wait_iff_congested() may help but no guarantee to help us.

If you still strongly worry about IPI cost, I'm concern to move drain_all_pages()
to more unfrequently point. but to ignore pcp makes less sense, IMHO.




WARNING: multiple messages have this Message-ID (diff)
From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: mgorman@suse.de
Cc: minchan.kim@gmail.com, abarry@cray.com,
	akpm@linux-foundation.org, linux-mm@kvack.org, riel@redhat.com,
	hannes@cmpxchg.org, linux-kernel@vger.kernel.org
Subject: Re: Unending loop in __alloc_pages_slowpath following OOM-kill; rfc: patch.
Date: Tue, 24 May 2011 18:40:31 +0900	[thread overview]
Message-ID: <4DDB7D0F.3060204@jp.fujitsu.com> (raw)
In-Reply-To: <20110524091611.GD5279@suse.de>

(2011/05/24 18:16), Mel Gorman wrote:
> On Tue, May 24, 2011 at 06:05:59PM +0900, KOSAKI Motohiro wrote:
>>>>> Why?
>>>>
>>>> Otherwise, we don't have good PCP dropping trigger. Big machine might have
>>>> big pcp cache.
>>>>
>>>
>>> Big machines also have a large cost for sending IPIs.
>>
>> Yes. But it's only matter if IPIs are frequently happen.
>> But, drain_all_pages() is NOT only IPI source. some vmscan function (e.g.
>> try_to_umap) makes a lot of IPIs.
>>
>> Then, it's _relatively_ not costly. I have a question. Do you compare which
>> operation and drain_all_pages()? IOW, your "costly" mean which scenario suspect?
>>
> 
> I am concerned that if the machine gets into trouble and we are failing
> to reclaim that sending more IPIs is not going to help any. There is no
> evidence at the moment that sending extra IPIs here will help anything.

In old days, we always call drain_all_pages() if did_some_progress!=0. But
current kernel only call it when get_page_from_freelist() fail. So,
wait_iff_congested() may help but no guarantee to help us.

If you still strongly worry about IPI cost, I'm concern to move drain_all_pages()
to more unfrequently point. but to ignore pcp makes less sense, IMHO.



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  reply	other threads:[~2011-05-24  9:40 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-05-13 21:31 Unending loop in __alloc_pages_slowpath following OOM-kill; rfc: patch Andrew Barry
2011-05-17 10:34 ` Minchan Kim
2011-05-17 11:34   ` Mel Gorman
2011-05-17 15:49   ` Andrew Barry
2011-05-18 22:29     ` Minchan Kim
2011-05-20 16:49       ` Minchan Kim
2011-05-20 16:49         ` Minchan Kim
2011-05-20 17:16         ` Rik van Riel
2011-05-20 17:16           ` Rik van Riel
2011-05-20 17:23         ` Mel Gorman
2011-05-20 17:23           ` Mel Gorman
2011-05-24  4:54         ` KOSAKI Motohiro
2011-05-24  4:54           ` KOSAKI Motohiro
2011-05-24  5:45           ` KOSAKI Motohiro
2011-05-24  5:45             ` KOSAKI Motohiro
2011-05-24  8:30           ` Mel Gorman
2011-05-24  8:30             ` Mel Gorman
2011-05-24  8:36             ` KOSAKI Motohiro
2011-05-24  8:36               ` KOSAKI Motohiro
2011-05-24  8:49               ` Mel Gorman
2011-05-24  8:49                 ` Mel Gorman
2011-05-24  9:05                 ` KOSAKI Motohiro
2011-05-24  9:05                   ` KOSAKI Motohiro
2011-05-24  9:16                   ` Mel Gorman
2011-05-24  9:16                     ` Mel Gorman
2011-05-24  9:40                     ` KOSAKI Motohiro [this message]
2011-05-24  9:40                       ` KOSAKI Motohiro
2011-05-24 10:57                       ` Mel Gorman
2011-05-24 10:57                         ` Mel Gorman
2011-05-24 23:53                         ` KOSAKI Motohiro
2011-05-24 23:53                           ` KOSAKI Motohiro
2011-05-24  8:34           ` Minchan Kim
2011-05-24  8:34             ` Minchan Kim
2011-05-24  8:41             ` KOSAKI Motohiro
2011-05-24  8:41               ` KOSAKI Motohiro
2011-05-24  8:57               ` Minchan Kim
2011-05-24  8:57                 ` Minchan Kim
2011-05-24  9:36                 ` KOSAKI Motohiro
2011-05-24  9:36                   ` KOSAKI Motohiro

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