• Jens Axboe's avatar
    block: attempt to merge with existing requests on plug flush · 5e84ea3a
    Jens Axboe authored
    One of the disadvantages of on-stack plugging is that we potentially
    lose out on merging since all pending IO isn't always visible to
    everybody. When we flush the on-stack plugs, right now we don't do
    any checks to see if potential merge candidates could be utilized.
    
    Correct this by adding a new insert variant, ELEVATOR_INSERT_SORT_MERGE.
    It works just ELEVATOR_INSERT_SORT, but first checks whether we can
    merge with an existing request before doing the insertion (if we fail
    merging).
    
    This fixes a regression with multiple processes issuing IO that
    can be merged.
    
    Thanks to Shaohua Li <shaohua.li@intel.com> for testing and fixing
    an accounting bug.
    Signed-off-by: default avatarJens Axboe <jaxboe@fusionio.com>
    5e84ea3a
blk-merge.c 11.1 KB