From: Johannes Weiner <hannes@cmpxchg.org>
To: Ric Mason <ric.masonn@gmail.com>
Cc: Raymond Jennings <shentino@gmail.com>,
Linux Memory Management List <linux-mm@kvack.org>
Subject: Re: Swap defragging
Date: Tue, 12 Mar 2013 12:53:47 -0400 [thread overview]
Message-ID: <20130312165347.GC1953@cmpxchg.org> (raw)
In-Reply-To: <513D4768.8050703@gmail.com>
On Mon, Mar 11, 2013 at 10:54:32AM +0800, Ric Mason wrote:
> Hi Johannes,
> On 03/08/2013 10:35 AM, Johannes Weiner wrote:
> >On Thu, Mar 07, 2013 at 06:07:23PM -0800, Raymond Jennings wrote:
> >>Just a two cent question, but is there any merit to having the kernel
> >>defragment swap space?
> >That is a good question.
> >
> >Swap does fragment quite a bit, and there are several reasons for
> >that.
> >
> >We swap pages in our LRU list order, but this list is sorted by first
> >access, not by access frequency (not quite that cookie cutter, but the
> >ordering is certainly fairly coarse). This means that the pages may
> >already be in suboptimal order for swap in at the time of swap out.
> >
> >Once written to disk, the layout tends to stick. One reason is that
> >we actually try to not free swap slots unless there is a shortage of
>
> If all the swap slots will be freed when swapoff?
Well, yeah, but that's hardly an interesting case, is it?
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next prev parent reply other threads:[~2013-03-12 16:53 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-08 2:07 Raymond Jennings
2013-03-08 2:35 ` Johannes Weiner
2013-03-08 3:01 ` Raymond Jennings
2013-03-09 2:00 ` Will Huck
2013-03-12 16:52 ` Johannes Weiner
2013-03-13 0:46 ` Will Huck
2013-03-13 1:31 ` Will Huck
2013-03-11 2:54 ` Ric Mason
2013-03-12 16:53 ` Johannes Weiner [this message]
2013-03-11 3:11 ` Simon Jeons
2013-03-12 17:03 ` Johannes Weiner
2013-03-11 3:16 ` Jaegeuk Hanse
2013-03-12 17:08 ` Johannes Weiner
2013-03-13 3:47 ` Jaegeuk Hanse
2013-03-11 6:24 ` Will Huck
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