From: Minchan Kim <minchan.kim@gmail.com>
To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: mgorman@suse.de, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, cl@linux.com
Subject: Re: [PATCH 1/3] mm: vmscan: Do use use PF_SWAPWRITE from zone_reclaim
Date: Tue, 12 Jul 2011 18:55:58 +0900 [thread overview]
Message-ID: <CAEwNFnAprEuZJucDSMgnUHGePyxgyRqNCWOsG0-K2nTjmKcUug@mail.gmail.com> (raw)
In-Reply-To: <4E1C1684.4090706@jp.fujitsu.com>
Hi KOSAKi,
On Tue, Jul 12, 2011 at 6:40 PM, KOSAKI Motohiro
<kosaki.motohiro@jp.fujitsu.com> wrote:
> (2011/07/12 18:27), Minchan Kim wrote:
>> Hi Mel,
>>
>> On Mon, Jul 11, 2011 at 10:01 PM, Mel Gorman <mgorman@suse.de> wrote:
>>> Zone reclaim is similar to direct reclaim in a number of respects.
>>> PF_SWAPWRITE is used by kswapd to avoid a write-congestion check
>>> but it's set also set for zone_reclaim which is inappropriate.
>>> Setting it potentially allows zone_reclaim users to cause large IO
>>> stalls which is worse than remote memory accesses.
>>
>> As I read zone_reclaim_mode in vm.txt, I think it's intentional.
>> It has meaning of throttle the process which are writing large amounts
>> of data. The point is to prevent use of remote node's free memory.
>>
>> And we has still the comment. If you're right, you should remove comment.
>> " * and we also need to be able to write out pages for RECLAIM_WRITE
>> * and RECLAIM_SWAP."
>>
>>
>> And at least, we should Cc Christoph and KOSAKI.
>
> Of course, I'll take full ack this. Do you remember I posted the same patch
> about one year ago. At that time, Mel disagreed me and I'm glad to see he changed
> the mind. :)
I remember that but I don't know why Mel didn't ack at that time.
http://lkml.org/lkml/2010/8/5/44
Anyway, Hannes's bd2f6199cf is to introduce lumpy reclaim of
zone_reclaim so it's natural to increase latency for getting big order
pages(ie, it's a trade-off).
And as I read about zone_reclaim_mode in Documentation/sysctl/vm.txt,
I think big latency(ie, throttling of the process) is intentional to
prevent stealing pages for other nodes.
If I am not against this patch, at least, we need agreement of
Christoph and others and if we agree this change, we changes vm.txt,
too.
--
Kind regards,
Minchan Kim
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next prev parent reply other threads:[~2011-07-12 9:56 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-11 13:01 [RFC PATCH 0/3] Reduce frequency of stalls due to zone_reclaim() on NUMA Mel Gorman
2011-07-11 13:01 ` [PATCH 1/3] mm: vmscan: Do use use PF_SWAPWRITE from zone_reclaim Mel Gorman
2011-07-12 9:27 ` Minchan Kim
2011-07-12 9:40 ` KOSAKI Motohiro
2011-07-12 9:55 ` Minchan Kim [this message]
2011-07-12 15:43 ` Christoph Lameter
2011-07-13 10:40 ` Mel Gorman
2011-07-12 10:14 ` Mel Gorman
2011-07-13 0:34 ` KOSAKI Motohiro
2011-07-11 13:01 ` [PATCH 2/3] mm: page allocator: Initialise ZLC for first zone eligible for zone_reclaim Mel Gorman
2011-07-13 1:15 ` KOSAKI Motohiro
2011-07-13 11:02 ` Mel Gorman
2011-07-14 1:20 ` KOSAKI Motohiro
2011-07-14 6:11 ` Mel Gorman
2011-07-11 13:01 ` [PATCH 3/3] mm: page allocator: Reconsider zones for allocation after direct reclaim Mel Gorman
2011-07-13 0:42 ` KOSAKI Motohiro
2011-07-13 11:10 ` Mel Gorman
2011-07-14 3:20 ` KOSAKI Motohiro
2011-07-14 6:10 ` Mel Gorman
2011-07-21 9:35 ` KOSAKI Motohiro
2011-07-21 10:31 ` Mel Gorman
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