> > Kashyap, I've also attached an updated patch for the elevator_count > > patch; if you agree John can include it in the next version. > > Hannes - Patch looks good. Header does not include problem statement. > How about adding below in header ? > > High CPU utilization on "native_queued_spin_lock_slowpath" due to lock > contention is possible in mq-deadline and bfq io scheduler when > nr_hw_queues is more than one. > It is because kblockd work queue can submit IO from all online CPUs > (through > blk_mq_run_hw_queues) even though only one hctx has pending commands. > Elevator callback "has_work" for mq-deadline and bfq scheduler consider > pending work if there are any IOs on request queue and it does not account > hctx context. Hannes/John - We need one more correction for below patch - https://github.com/hisilicon/kernel-dev/commit/ff631eb80aa0449eaeb78a282fd7eff2a9e42f77 I noticed - that elevator_queued count goes negative mainly because there are some case where IO was submitted from dispatch queue(not scheduler queue) and request still has "RQF_ELVPRIV" flag set. In such cases " dd_finish_request" is called without " dd_insert_request". I think it is better to decrement counter once it is taken out from dispatched queue. (Ming proposed to use dispatch path for decrementing counter, but I somehow did not accounted assuming RQF_ELVPRIV will be set only if IO is submitted from scheduler queue.) Below is additional change. Can you merge this ? diff --git a/block/mq-deadline.c b/block/mq-deadline.c index 9d75374..bc413dd 100644 --- a/block/mq-deadline.c +++ b/block/mq-deadline.c @@ -385,6 +385,8 @@ static struct request *dd_dispatch_request(struct blk_mq_hw_ctx *hctx) spin_lock(&dd->lock); rq = __dd_dispatch_request(dd); + if (rq) + atomic_dec(&rq->mq_hctx->elevator_queued); spin_unlock(&dd->lock); return rq; @@ -574,7 +576,6 @@ static void dd_finish_request(struct request *rq) blk_mq_sched_mark_restart_hctx(rq->mq_hctx); spin_unlock_irqrestore(&dd->zone_lock, flags); } - atomic_dec(&rq->mq_hctx->elevator_queued); } static bool dd_has_work(struct blk_mq_hw_ctx *hctx) -- 2.9.5 Kashyap
