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    SubjectRe: [PATCH]swap-zero-page-bug
    On Wed, 29 Oct 2008, Li Xiaodong wrote:

    > According to Documentation/filesystems/proc.txt, kernel should swap one page
    > as is 0, while it seems not like so in mm/swapfile.c:
    > ...
    > int our_page_cluster = page_cluster;
    > ...
    > if (!our_page_cluster) /* no readahead */
    > return 0;
    > ...
    > It is better to remove that checkpoint.

    No, page_cluster 0 allows swapin one page at a time, but disallows
    swapin readahead (better named readaround) i.e. disallows reading
    more than the one page actually requested.

    Compare with how valid_swaphandles() is used from swapin_readahead():
    there's actually one extra call to read_swap_cache_async() - because
    we must ignore failure on the readaround but not on the page requested.

    That "return 0" avoids the overhead of a pointlessly doubled
    read_swap_cache_async() when there's only one page to be read.

    Your patch might be needed if you'd found that swapin of one page
    was not working at all - but you'd be making a stronger case if
    you'd found that, I think!


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      Last update: 2008-11-01 11:37    [W:0.020 / U:11.912 seconds]
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