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    Subject[PATCH 0/3 v5][RFC] ext3/4: enhance fsync performance when using CFQ
    Date
    Hi,

    Running iozone with the fsync flag, or fs_mark, the performance of CFQ is
    far worse than that of deadline for enterprise class storage when dealing
    with file sizes of 8MB or less. I used the following command line as a
    representative test case:

    fs_mark -S 1 -D 10000 -N 100000 -d /mnt/test/fs_mark -s 65536 -t 1 -w 4096 -F

    When run using the deadline I/O scheduler, an average of the first 5 numbers
    will give you 448.4 files / second. CFQ will yield only 106.7. With
    this patch series applied (and the two patches I sent yesterday), CFQ now
    achieves 462.5 files / second.

    This patch set is still an RFC. I'd like to make it perform better when
    there is a competing sequential reader present. For now, I've addressed
    the concerns voiced about the previous posting.

    Review and testing would be greatly appreciated.

    Thanks!
    Jeff

    ---

    New from the last round:

    - removed the think time calculation I added for the sync-noidle service tree
    - replaced above with a suggestion from Vivek to only guard against currently
    active sequential readers when determining if we can preempt the sync-noidle
    service tree.
    - bug fixes

    Over all, I think it's simpler now thanks to the suggestions from Jens and
    Vivek.

    [PATCH 1/3] block: Implement a blk_yield function to voluntarily give up the I/O scheduler.
    [PATCH 2/3] jbd: yield the device queue when waiting for commits
    [PATCH 3/3] jbd2: yield the device queue when waiting for journal commits


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