• Dan Williams's avatar
    block: strict rq_affinity · 5757a6d7
    Dan Williams authored
    Some systems benefit from completions always being steered to the strict
    requester cpu rather than the looser "per-socket" steering that
    blk_cpu_to_group() attempts by default. This is because the first
    CPU in the group mask ends up being completely overloaded with work,
    while the others (including the original submitter) has power left
    to spare.
    
    Allow the strict mode to be set by writing '2' to the sysfs control
    file. This is identical to the scheme used for the nomerges file,
    where '2' is a more aggressive setting than just being turned on.
    
    echo 2 > /sys/block/<bdev>/queue/rq_affinity
    
    Cc: Christoph Hellwig <hch@infradead.org>
    Cc: Roland Dreier <roland@purestorage.com>
    Tested-by: default avatarDave Jiang <dave.jiang@intel.com>
    Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
    Signed-off-by: default avatarJens Axboe <jaxboe@fusionio.com>
    5757a6d7
blk-softirq.c 4.2 KB