From: Andrea Arcangeli <aarcange@redhat.com>
To: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Shaohua Li <shli@kernel.org>,
linux-mm@kvack.org
Subject: Re: [patch 1/2 v2]compaction: abort compaction loop if lock is contended or run too long
Date: Thu, 13 Sep 2012 19:11:27 +0200 [thread overview]
Message-ID: <20120913171127.GI3388@redhat.com> (raw)
In-Reply-To: <20120913163151.GC11266@suse.de>
On Thu, Sep 13, 2012 at 05:31:51PM +0100, Mel Gorman wrote:
> On Thu, Sep 13, 2012 at 06:04:32PM +0200, Andrea Arcangeli wrote:
> > On Thu, Sep 13, 2012 at 10:38:26AM +0100, Mel Gorman wrote:
> > > I agree with Minchan. Andrea's patch ignores the fact that free page
> > > isolation might have aborted due to lock contention. It's not necessarily
> > > going to be isolating the pages it needs for migration.
> >
> > Actually I thought of calling putback_lru_pages first, but then I
> > thought it was better to just complete the current slice.
> >
>
> Unfortunately that will end up calling compaction_alloc() ->
> isolate_freepages and probably end up contending again.
>
> > Note that putback_lru_pages can take the lru_lock immediately too when
>
> True, but in that case there is no choice in the matter. We can't just
> leak the pages.
This is why in that case (if the contention was generated by the
lru_lock) we would be better off to go ahead and do migrate_pages.
We could track contended_lru_lock and contended_zone_lock separately
to know if it's that case or not, but then I doubt it matters that much.
> To me, that will just contend more than we have to. We're aborting compaction
> and finishing off the current slice will not make any meaningful difference
> to whether tha allocation succeeds or not.
If you prefer the putback_lru_pages I'm fine, I only wanted to clarify
neither of the two solutions is going to do the optimal thing at all
times.
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next prev parent reply other threads:[~2012-09-13 17:11 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-10 1:18 [patch 1/2 v2]compaction: abort compaction loop if lock is contended or run too long Shaohua Li
2012-09-10 8:11 ` Mel Gorman
2012-09-11 1:45 ` Minchan Kim
2012-09-11 8:29 ` Shaohua Li
2012-09-11 8:40 ` Minchan Kim
2012-09-11 23:34 ` Andrew Morton
2012-09-12 0:48 ` Andrea Arcangeli
2012-09-12 21:20 ` Andrew Morton
2012-09-12 23:48 ` Andrea Arcangeli
2012-09-13 0:47 ` Minchan Kim
2012-09-13 2:49 ` Shaohua Li
2012-09-13 9:38 ` Mel Gorman
2012-09-13 10:13 ` Shaohua Li
2012-09-13 16:04 ` Andrea Arcangeli
2012-09-13 16:31 ` Mel Gorman
2012-09-13 17:11 ` Andrea Arcangeli [this message]
2012-09-13 10:03 ` Mel Gorman
2012-09-12 11:08 ` Mel Gorman
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