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    blk-mq: use sparser tag layout for lower queue depth · 59d13bf5
    Jens Axboe 提交于
    For best performance, spreading tags over multiple cachelines
    makes the tagging more efficient on multicore systems. But since
    we have 8 * sizeof(unsigned long) tags per cacheline, we don't
    always get a nice spread.
    
    Attempt to spread the tags over at least 4 cachelines, using fewer
    number of bits per unsigned long if we have to. This improves
    tagging performance in setups with 32-128 tags. For higher depths,
    the spread is the same as before (BITS_PER_LONG tags per cacheline).
    Signed-off-by: NJens Axboe <axboe@fb.com>
    59d13bf5
blk-mq-tag.c 10.2 KB