From: Johannes Weiner <hannes@cmpxchg.org>
To: Rik van Riel <riel@redhat.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
KOSAKI Motohiro <kosaki.motohiro@gmail.com>,
akpm@linux-foundation.org, mel@csn.ul.ie, minchan.kim@gmail.com
Subject: Re: [PATCH v2 -mm] make swapin readahead skip over holes
Date: Wed, 11 Jan 2012 22:42:42 +0100 [thread overview]
Message-ID: <20120111214242.GF24386@cmpxchg.org> (raw)
In-Reply-To: <4F0DFF64.4040704@redhat.com>
On Wed, Jan 11, 2012 at 04:30:12PM -0500, Rik van Riel wrote:
> On 01/11/2012 04:10 PM, Johannes Weiner wrote:
> >On Wed, Jan 11, 2012 at 02:30:44PM -0500, 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.
> >>
> >>The checks done in valid_swaphandles are already done in
> >>read_swap_cache_async as well, allowing us to remove a fair amount
> >>of code.
> >
> >__swap_duplicate() also checks for whether the offset is within the
> >swap device range. Do you think we could remove get_swap_cluster()
> >altogether and just try reading the aligned page_cluster range?
>
> That is how I implemented it originally, but we need
> to take the swap_lock so it is cleaner to implement
> a helper function in swapfile.c :)
AFAICS, it's only needed to validate the offset against si->max, but
this too is done in __swap_duplicate().
What's otherwise left is just rounding down swp_offset(entry) and
adding 1 << page_cluster to it, that shouldn't need the swap_lock?
Am I missing something?
--
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/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2012-01-11 21:42 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-11 19:30 Rik van Riel
2012-01-11 21:10 ` Johannes Weiner
2012-01-11 21:30 ` Rik van Riel
2012-01-11 21:42 ` Johannes Weiner [this message]
2012-01-11 21:58 ` Rik van Riel
2012-01-12 14:53 ` Mel Gorman
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=20120111214242.GF24386@cmpxchg.org \
--to=hannes@cmpxchg.org \
--cc=akpm@linux-foundation.org \
--cc=kosaki.motohiro@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mel@csn.ul.ie \
--cc=minchan.kim@gmail.com \
--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