From: Pavel Begunkov <[email protected]> blk_stat_add() calls {get,put}_cpu_ptr() in a loop, which entails overhead of disabling/enabling preemption. The loop is under RCU (i.e.short) anyway, so do get_cpu() in advance.
Signed-off-by: Pavel Begunkov <[email protected]> --- block/blk-stat.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/block/blk-stat.c b/block/blk-stat.c index d892ad2cb938..4239954b0bce 100644 --- a/block/blk-stat.c +++ b/block/blk-stat.c @@ -75,7 +75,7 @@ void blk_stat_add(struct request *rq, u64 now) struct request_queue *q = rq->q; struct blk_stat_callback *cb; struct blk_rq_stat_staging *stat; - int bucket; + int bucket, cpu; u64 value; value = (now >= rq->io_start_time_ns) ? now - rq->io_start_time_ns : 0; @@ -83,6 +83,7 @@ void blk_stat_add(struct request *rq, u64 now) blk_throtl_stat_add(rq, value); rcu_read_lock(); + cpu = get_cpu(); list_for_each_entry_rcu(cb, &q->stats->callbacks, list) { if (!blk_stat_is_active(cb)) continue; @@ -91,10 +92,10 @@ void blk_stat_add(struct request *rq, u64 now) if (bucket < 0) continue; - stat = &get_cpu_ptr(cb->cpu_stat)[bucket]; + stat = &per_cpu_ptr(cb->cpu_stat, cpu)[bucket]; blk_rq_stat_add(stat, value); - put_cpu_ptr(cb->cpu_stat); } + put_cpu(); rcu_read_unlock(); } -- 2.23.0
