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    SubjectRe: [PATCH v2 -mm] make swapin readahead skip over holes
    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 :)

     \ /
      Last update: 2012-01-11 22:33    [W:0.036 / U:11.796 seconds]
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