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    Subject[PATCH v2 3/3] blk-mq: optimise *end_request non-stat path
    Date
    We already have a blk_mq_need_time_stamp() check in
    __blk_mq_end_request() to get a timestamp, hide all the statistics
    accounting under it. It cuts some cycles for requests that don't need
    stats, and is free otherwise.

    Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
    ---
    block/blk-mq.c | 18 ++++++++----------
    1 file changed, 8 insertions(+), 10 deletions(-)

    diff --git a/block/blk-mq.c b/block/blk-mq.c
    index 38e6651d8b94..3dd3b22bc280 100644
    --- a/block/blk-mq.c
    +++ b/block/blk-mq.c
    @@ -572,20 +572,18 @@ void blk_mq_free_plug_rqs(struct blk_plug *plug)

    inline void __blk_mq_end_request(struct request *rq, blk_status_t error)
    {
    - u64 now = 0;
    + if (blk_mq_need_time_stamp(rq)) {
    + u64 now = ktime_get_ns();

    - if (blk_mq_need_time_stamp(rq))
    - now = ktime_get_ns();
    + if (rq->rq_flags & RQF_STATS) {
    + blk_mq_poll_stats_start(rq->q);
    + blk_stat_add(rq, now);
    + }

    - if (rq->rq_flags & RQF_STATS) {
    - blk_mq_poll_stats_start(rq->q);
    - blk_stat_add(rq, now);
    + blk_mq_sched_completed_request(rq, now);
    + blk_account_io_done(rq, now);
    }

    - blk_mq_sched_completed_request(rq, now);
    -
    - blk_account_io_done(rq, now);
    -
    if (rq->end_io) {
    rq_qos_done(rq->q, rq);
    rq->end_io(rq, error);
    --
    2.33.0
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