Re: [PATCH -mm] make swapin readahead skip over holes

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(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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