From: Michal Hocko <mhocko@suse.cz>
To: Roman Gushchin <klamm@yandex-team.ru>
Cc: David Rientjes <rientjes@google.com>,
Christoph Lameter <cl@gentwo.org>,
penberg@kernel.org, mpm@selenic.com, akpm@linux-foundation.org,
mgorman@suse.de, 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: Mon, 17 Jun 2013 16:27:15 +0200 [thread overview]
Message-ID: <20130617142715.GB8853@dhcp22.suse.cz> (raw)
In-Reply-To: <51BF024F.2080609@yandex-team.ru>
On Mon 17-06-13 16:34:23, Roman Gushchin wrote:
> On 15.06.2013 00:26, David Rientjes wrote:
> >On Fri, 14 Jun 2013, Christoph Lameter wrote:
> >
> >>>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?
> >>
> >
> >I'm surprised you like this patch, it basically makes slub allocations to
> >be atomic and doesn't try memory compaction nor reclaim. Asynchronous
> >compaction certainly isn't aggressive enough to mimick the effects of the
> >old lumpy reclaim that would have resulted in less fragmented memory. If
> >slub is the only thing that is doing high-order allocations, it will start
> >falling back to the smallest page order much much more often.
> >
> >I agree that this doesn't seem like a slub issue at all but rather a page
> >allocator issue; if we have many simultaneous thp faults at the same time
> >and /sys/kernel/mm/transparent_hugepage/defrag is "always" then you'll get
> >the same problem if deferred compaction isn't helping.
> >
> >So I don't think we should be patching slub in any special way here.
> >
> >Roman, are you using the latest kernel? If so, what does
> >grep compact_ /proc/vmstat show after one or more of these events?
> >
>
> We're using 3.4. And the problem reveals when we moved from 3.2 to 3.4.
> It can be also reproduced on 3.5.
FWIW, there were some compaction locking related patches merged
around 3.7. See 2a1402aa044b55c2d30ab0ed9405693ef06fb07c and follow ups.
> I'll send the exact numbers as soon I'll reproduce it again.
> It can take up to 1 week.
>
> Thanks!
>
> Regards,
> Roman
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@kvack.org. For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2013-06-17 14:27 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
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 [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20130617142715.GB8853@dhcp22.suse.cz \
--to=mhocko@suse.cz \
--cc=akpm@linux-foundation.org \
--cc=cl@gentwo.org \
--cc=glommer@parallels.com \
--cc=hannes@cmpxchg.org \
--cc=jiang.liu@huawei.com \
--cc=klamm@yandex-team.ru \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mgorman@suse.de \
--cc=minchan@kernel.org \
--cc=mpm@selenic.com \
--cc=penberg@kernel.org \
--cc=rientjes@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).