From: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
To: Rik van Riel <riel@redhat.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
akpm@linux-foundation.org, Mel Gorman <mel@csn.ul.ie>,
Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [PATCH -mm] make swapin readahead skip over holes
Date: Mon, 09 Jan 2012 18:49:51 -0500 [thread overview]
Message-ID: <4F0B7D1F.7040802@gmail.com> (raw)
In-Reply-To: <20120109181023.7c81d0be@annuminas.surriel.com>
(1/9/12 6:10 PM), Rik van Riel wrote:
> Ever since abandoning the virtual scan of processes, for scalability
> reasons, swap space has been a little more fragmented than before.
> This can lead to the situation where a large memory user is killed,
> swap space ends up full of "holes" and swapin readahead is totally
> ineffective.
>
> On my home system, after killing a leaky firefox it took over an
> hour to page just under 2GB of memory back in, slowing the virtual
> machines down to a crawl.
>
> This patch makes swapin readahead simply skip over holes, instead
> of stopping at them. This allows the system to swap things back in
> at rates of several MB/second, instead of a few hundred kB/second.
If I understand correctly, this patch have
Pros
- increase IO throughput
Cons
- increase a risk to pick up unrelated swap entries by swap readahead
The changelog explained former but doesn't explained latter. I'm a bit
hesitate now.
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WARNING: multiple messages have this Message-ID (diff)
From: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
To: Rik van Riel <riel@redhat.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
akpm@linux-foundation.org, Mel Gorman <mel@csn.ul.ie>,
Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [PATCH -mm] make swapin readahead skip over holes
Date: Mon, 09 Jan 2012 18:49:51 -0500 [thread overview]
Message-ID: <4F0B7D1F.7040802@gmail.com> (raw)
In-Reply-To: <20120109181023.7c81d0be@annuminas.surriel.com>
(1/9/12 6:10 PM), Rik van Riel wrote:
> Ever since abandoning the virtual scan of processes, for scalability
> reasons, swap space has been a little more fragmented than before.
> This can lead to the situation where a large memory user is killed,
> swap space ends up full of "holes" and swapin readahead is totally
> ineffective.
>
> On my home system, after killing a leaky firefox it took over an
> hour to page just under 2GB of memory back in, slowing the virtual
> machines down to a crawl.
>
> This patch makes swapin readahead simply skip over holes, instead
> of stopping at them. This allows the system to swap things back in
> at rates of several MB/second, instead of a few hundred kB/second.
If I understand correctly, this patch have
Pros
- increase IO throughput
Cons
- increase a risk to pick up unrelated swap entries by swap readahead
The changelog explained former but doesn't explained latter. I'm a bit
hesitate now.
next prev parent reply other threads:[~2012-01-09 23:49 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-09 23:10 [PATCH -mm] make swapin readahead skip over holes Rik van Riel
2012-01-09 23:10 ` Rik van Riel
2012-01-09 23:49 ` KOSAKI Motohiro [this message]
2012-01-09 23:49 ` KOSAKI Motohiro
2012-01-10 3:09 ` Rik van Riel
2012-01-10 3:09 ` Rik van Riel
2012-01-11 7:14 ` KOSAKI Motohiro
2012-01-11 7:14 ` KOSAKI Motohiro
2012-01-11 8:01 ` KOSAKI Motohiro
2012-01-11 8:01 ` KOSAKI Motohiro
2012-01-11 8:05 ` KOSAKI Motohiro
2012-01-11 8:05 ` KOSAKI Motohiro
2012-01-11 14:11 ` John Stoffel
2012-01-11 14:11 ` John Stoffel
2012-01-11 19:17 ` Christoph Lameter
2012-01-11 19:17 ` Christoph Lameter
2012-01-11 21:03 ` John Stoffel
2012-01-11 21:03 ` John Stoffel
2012-01-11 22:25 ` KOSAKI Motohiro
2012-01-11 22:25 ` KOSAKI Motohiro
2012-01-11 23:15 ` Andrew Morton
2012-01-11 23:15 ` Andrew Morton
2012-01-11 16:51 ` Mel Gorman
2012-01-11 16:51 ` Mel Gorman
2012-01-11 19:23 ` Rik van Riel
2012-01-11 19:23 ` Rik van Riel
2012-01-12 14:33 ` Mel Gorman
2012-01-12 14:33 ` Mel Gorman
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