From: Mel Gorman <mel@csn.ul.ie>
To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Rik van Riel <riel@redhat.com>,
Johannes Weiner <hannes@cmpxchg.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/3] mm,vmscan: Reclaim order-0 and compact instead of lumpy reclaim when under light pressure
Date: Mon, 15 Nov 2010 09:22:56 +0000 [thread overview]
Message-ID: <20101115092256.GE27362@csn.ul.ie> (raw)
In-Reply-To: <20101114150039.E028.A69D9226@jp.fujitsu.com>
On Sun, Nov 14, 2010 at 03:02:03PM +0900, KOSAKI Motohiro wrote:
> > On Thu, Nov 11, 2010 at 07:07:04PM +0000, Mel Gorman wrote:
> > > + if (COMPACTION_BUILD)
> > > + sc->lumpy_reclaim_mode = LUMPY_MODE_COMPACTION;
> > > + else
> > > + sc->lumpy_reclaim_mode = LUMPY_MODE_CONTIGRECLAIM;
> > >
> >
> > Gack, I posted the slightly wrong version. This version prevents lumpy
> > reclaim ever being used. The figures I posted were for a patch where
> > this condition looked like
> >
> > if (COMPACTION_BUILD && priority > DEF_PRIORITY - 2)
> > sc->lumpy_reclaim_mode = LUMPY_MODE_COMPACTION;
> > else
> > sc->lumpy_reclaim_mode = LUMPY_MODE_CONTIGRECLAIM;
>
> Can you please tell us your opinition which is better 1) automatically turn lumby on
> by priority (this approach) 2) introduce GFP_LUMPY (andrea proposed). I'm not
> sure which is better, then I'd like to hear both pros/cons concern.
>
That's a very good question!
The main "pro" of using lumpy reclaim is that it has been tested. It's known
to be very heavy and disrupt the system but it's also known to work. Lumpy
reclaim is also less suspectible to allocation races than compaction is
i.e. if memory is low, compaction requires that X number of pages be free
where as lumpy frees the pages it requires.
GFP_LUMPY is something else and is only partially related. Transparent Huge
Pages (THP) does not want to hit lumpy reclaim no matter what the circumstances
are - It is always better for THP to not use lumpy reclaim. It's debatable
whether it should even reclaim order-0 pages for compaction so even with
this series, THP might still introduce GFP_LUMPY.
Does this answer your question?
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
next prev parent reply other threads:[~2010-11-15 9:23 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-11 19:07 [RFC PATCH 0/3] Use compaction to reduce a dependency on lumpy reclaim Mel Gorman
2010-11-11 19:07 ` [PATCH 1/3] mm,vmscan: Convert lumpy_mode into a bitmask Mel Gorman
2010-11-14 5:40 ` KOSAKI Motohiro
2010-11-15 9:16 ` Mel Gorman
2010-11-11 19:07 ` [PATCH 2/3] mm,compaction: Add COMPACTION_BUILD Mel Gorman
2010-11-14 5:45 ` KOSAKI Motohiro
2010-11-15 9:26 ` Mel Gorman
2010-11-11 19:07 ` [PATCH 3/3] mm,vmscan: Reclaim order-0 and compact instead of lumpy reclaim when under light pressure Mel Gorman
2010-11-12 9:37 ` Mel Gorman
2010-11-14 5:43 ` KOSAKI Motohiro
2010-11-15 9:17 ` Mel Gorman
2010-11-14 6:02 ` KOSAKI Motohiro
2010-11-15 9:22 ` Mel Gorman [this message]
2010-11-15 15:23 ` Andrea Arcangeli
2010-11-14 5:59 ` KOSAKI Motohiro
2010-11-15 9:25 ` Mel Gorman
2010-11-14 5:31 ` [RFC PATCH 0/3] Use compaction to reduce a dependency on lumpy reclaim KOSAKI Motohiro
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=20101115092256.GE27362@csn.ul.ie \
--to=mel@csn.ul.ie \
--cc=aarcange@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=hannes@cmpxchg.org \
--cc=kosaki.motohiro@jp.fujitsu.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=riel@redhat.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).