From: Rik van Riel <riel@redhat.com>
To: David Rientjes <rientjes@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mgorman@suse.de>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Minchan Kim <minchan@kernel.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [patch] mm, thp: abort compaction if migration page cannot be charged to memcg
Date: Mon, 25 Jun 2012 16:40:45 -0400 [thread overview]
Message-ID: <4FE8CCCD.7080503@redhat.com> (raw)
In-Reply-To: <alpine.DEB.2.00.1206202351030.28770@chino.kir.corp.google.com>
On 06/21/2012 02:52 AM, David Rientjes wrote:
> If page migration cannot charge the new page to the memcg,
> migrate_pages() will return -ENOMEM. This isn't considered in memory
> compaction however, and the loop continues to iterate over all pageblocks
> trying in a futile attempt to continue migrations which are only bound to
> fail.
>
> This will short circuit and fail memory compaction if migrate_pages()
> returns -ENOMEM. COMPACT_PARTIAL is returned in case some migrations
> were successful so that the page allocator will retry.
The patch makes sense, however I wonder if it would make
more sense in the long run to allow migrate/compaction to
temporarily exceed the memcg memory limit for a cgroup,
because the original page will get freed again soon anyway.
That has the potential to improve compaction success, and
reduce compaction related CPU use.
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WARNING: multiple messages have this Message-ID (diff)
From: Rik van Riel <riel@redhat.com>
To: David Rientjes <rientjes@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mgorman@suse.de>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Minchan Kim <minchan@kernel.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [patch] mm, thp: abort compaction if migration page cannot be charged to memcg
Date: Mon, 25 Jun 2012 16:40:45 -0400 [thread overview]
Message-ID: <4FE8CCCD.7080503@redhat.com> (raw)
In-Reply-To: <alpine.DEB.2.00.1206202351030.28770@chino.kir.corp.google.com>
On 06/21/2012 02:52 AM, David Rientjes wrote:
> If page migration cannot charge the new page to the memcg,
> migrate_pages() will return -ENOMEM. This isn't considered in memory
> compaction however, and the loop continues to iterate over all pageblocks
> trying in a futile attempt to continue migrations which are only bound to
> fail.
>
> This will short circuit and fail memory compaction if migrate_pages()
> returns -ENOMEM. COMPACT_PARTIAL is returned in case some migrations
> were successful so that the page allocator will retry.
The patch makes sense, however I wonder if it would make
more sense in the long run to allow migrate/compaction to
temporarily exceed the memcg memory limit for a cgroup,
because the original page will get freed again soon anyway.
That has the potential to improve compaction success, and
reduce compaction related CPU use.
next prev parent reply other threads:[~2012-06-25 20:41 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-21 6:52 [patch] mm, thp: abort compaction if migration page cannot be charged to memcg David Rientjes
2012-06-21 6:52 ` David Rientjes
2012-06-21 8:11 ` Minchan Kim
2012-06-21 8:11 ` Minchan Kim
2012-06-21 8:30 ` David Rientjes
2012-06-21 8:30 ` David Rientjes
2012-06-21 9:01 ` David Rientjes
2012-06-21 9:01 ` David Rientjes
2012-06-21 10:05 ` Kamezawa Hiroyuki
2012-06-21 10:05 ` Kamezawa Hiroyuki
2012-06-21 10:16 ` David Rientjes
2012-06-21 10:16 ` David Rientjes
2012-06-21 9:32 ` Mel Gorman
2012-06-21 9:32 ` Mel Gorman
2012-06-21 9:57 ` David Rientjes
2012-06-21 9:57 ` David Rientjes
2012-06-25 20:40 ` Rik van Riel [this message]
2012-06-25 20:40 ` Rik van Riel
2012-06-26 0:32 ` David Rientjes
2012-06-26 0:32 ` David Rientjes
2012-06-26 3:11 ` Kamezawa Hiroyuki
2012-06-26 3:11 ` Kamezawa Hiroyuki
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