From: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: kosaki.motohiro@gmail.com, linux-kernel@vger.kernel.org,
linux-mm@kvack.org,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Mel Gorman <mgorman@suse.de>
Subject: Re: [PATCH] mm: __rmqueue_fallback() should respect pageblock type
Date: Thu, 31 Oct 2013 01:00:40 -0400 [thread overview]
Message-ID: <5271E3F8.80108@gmail.com> (raw)
In-Reply-To: <20131030213537.f346d751.akpm@linux-foundation.org>
(10/31/13 12:35 AM), Andrew Morton wrote:
> On Thu, 31 Oct 2013 00:24:49 -0400 kosaki.motohiro@gmail.com wrote:
>
>> When __rmqueue_fallback() don't find out a free block with the same size
>> of required, it splits a larger page and puts back rest peiece of the page
>> to free list.
>>
>> But it has one serious mistake. When putting back, __rmqueue_fallback()
>> always use start_migratetype if type is not CMA. However, __rmqueue_fallback()
>> is only called when all of start_migratetype queue are empty. That said,
>> __rmqueue_fallback always put back memory to wrong queue except
>> try_to_steal_freepages() changed pageblock type (i.e. requested size is
>> smaller than half of page block). Finally, antifragmentation framework
>> increase fragmenation instead of decrease.
>>
>> Mel's original anti fragmentation do the right thing. But commit 47118af076
>> (mm: mmzone: MIGRATE_CMA migration type added) broke it.
>>
>> This patch restores sane and old behavior.
>
> What are the user-visible runtime effects of this change?
Memory fragmentation may increase compaction rate. (And then system get unnecessary
slow down)
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next prev parent reply other threads:[~2013-10-31 5:00 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-31 4:24 [PATCH] mm: __rmqueue_fallback() should respect pageblock type kosaki.motohiro
2013-10-31 4:35 ` Andrew Morton
2013-10-31 5:00 ` KOSAKI Motohiro [this message]
2013-10-31 5:15 ` KOSAKI Motohiro
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