From: Christoph Lameter <cl@gentwo.org>
To: Roman Gushchin <klamm@yandex-team.ru>
Cc: penberg@kernel.org, mpm@selenic.com, akpm@linux-foundation.org,
mgorman@suse.de, rientjes@google.com, glommer@parallels.com,
hannes@cmpxchg.org, minchan@kernel.org, jiang.liu@huawei.com,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] slub: Avoid direct compaction if possible
Date: Fri, 14 Jun 2013 14:32:11 +0000 [thread overview]
Message-ID: <0000013f4319cb46-a5a3de58-1207-4037-ae39-574b58135ea2-000000@email.amazonses.com> (raw)
In-Reply-To: <51BB1802.8050108@yandex-team.ru>
On Fri, 14 Jun 2013, Roman Gushchin wrote:
> Slub tries to allocate contiguous pages even if memory is fragmented and
> there are no free contiguous pages. In this case it calls direct compaction
> to allocate contiguous page. Compaction requires the taking of some heavily
> contended locks (e.g. zone locks). So, running compaction (direct and using
> kswapd) simultaneously on several processors can cause serious performance
> issues.
The main thing that this patch does is to add a nocompact flag to the page
allocator. That needs to be a separate patch. Also fix the description.
Slub does not invoke compaction. The page allocator initiates compaction
under certain conditions.
> It's possible to avoid such problems (or at least to make them less probable)
> by avoiding direct compaction. If it's not possible to allocate a contiguous
> page without compaction, slub will fall back to order 0 page(s). In this case
> kswapd will be woken to perform asynchronous compaction. So, slub can return
> to default order allocations as soon as memory will be de-fragmented.
Sounds like a good idea. Do you have some numbers to show the effect of
this patch?
next prev parent reply other threads:[~2013-06-14 14:32 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-14 13:17 [PATCH] slub: Avoid direct compaction if possible Roman Gushchin
2013-06-14 14:32 ` Christoph Lameter [this message]
2013-06-14 15:17 ` Roman Gushchin
2013-06-14 16:08 ` Christoph Lameter
2013-06-14 16:52 ` Roman Gushchin
2013-06-14 20:26 ` David Rientjes
2013-06-17 12:34 ` Roman Gushchin
2013-06-17 14:27 ` Michal Hocko
2013-06-17 14:54 ` Roman Gushchin
2013-06-17 21:44 ` David Rientjes
2013-06-27 8:49 ` Roman Gushchin
2013-06-27 20:41 ` David Rientjes
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