From: Rik van Riel <riel@redhat.com>
To: Johannes Weiner <hannes@cmpxchg.org>
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 16:30:12 -0500 [thread overview]
Message-ID: <4F0DFF64.4040704@redhat.com> (raw)
In-Reply-To: <20120111205041.GE24386@cmpxchg.org>
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 :)
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next prev parent reply other threads:[~2012-01-11 21:30 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-11 19:30 [PATCH v2 -mm] make swapin readahead skip over holes Rik van Riel
2012-01-11 21:10 ` Johannes Weiner
2012-01-11 21:30 ` Rik van Riel [this message]
2012-01-11 21:42 ` Johannes Weiner
2012-01-11 21:58 ` Rik van Riel
2012-01-12 14:53 ` Mel Gorman
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