On Mon, Oct 18, 2021 at 09:08:57AM +0100, John Garry wrote: > On 13/10/2021 16:13, John Garry wrote: > > > diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c > > > index 72a2724a4eee..2a2ad6dfcc33 100644 > > > --- a/block/blk-mq-tag.c > > > +++ b/block/blk-mq-tag.c > > > @@ -232,8 +232,9 @@ static bool bt_iter(struct sbitmap *bitmap, > > > unsigned int bitnr, void *data) > > > if (!rq) > > > return true; > > > - if (rq->q == hctx->queue && rq->mq_hctx == hctx) > > > - ret = iter_data->fn(hctx, rq, iter_data->data, reserved); > > > + if (rq->q == hctx->queue && (rq->mq_hctx == hctx || > > > + blk_mq_is_shared_tags(hctx->flags))) > > > + ret = iter_data->fn(rq->mq_hctx, rq, iter_data->data, reserved); > > > blk_mq_put_rq_ref(rq); > > > return ret; > > > } > > > @@ -460,6 +461,9 @@ void blk_mq_queue_tag_busy_iter(struct > > > request_queue *q, busy_iter_fn *fn, > > > if (tags->nr_reserved_tags) > > > bt_for_each(hctx, &tags->breserved_tags, fn, priv, true); > > > bt_for_each(hctx, &tags->bitmap_tags, fn, priv, false); > > > + > > > + if (blk_mq_is_shared_tags(hctx->flags)) > > > + break; > > > } > > > blk_queue_exit(q); > > > } > > > > > > > I suppose that is ok, and means that we iter once. > > > > However, I have to ask, where is the big user of > > blk_mq_queue_tag_busy_iter() coming from? I saw this from Kashyap's > > mail: > > > > > 1.31% 1.31% kworker/57:1H-k [kernel.vmlinux] > > > native_queued_spin_lock_slowpath > > > ret_from_fork > > > kthread > > > worker_thread > > > process_one_work > > > blk_mq_timeout_work > > > blk_mq_queue_tag_busy_iter > > > bt_iter > > > blk_mq_find_and_get_req > > > _raw_spin_lock_irqsave > > > native_queued_spin_lock_slowpath > > > > How or why blk_mq_timeout_work()? > > Just some update: I tried hisi_sas with 10x SAS SSDs, megaraid sas with 1x > SATA HDD (that's all I have), and null blk with lots of devices, and I still > can't see high usage of blk_mq_queue_tag_busy_iter(). It should be triggered easily in case of heavy io accounting: while true; do cat /proc/diskstats; done > So how about we get this patch processed (to fix blk_mq_tagset_busy_iter()), > as it is independent of blk_mq_queue_tag_busy_iter()? And then wait for some > update or some more info from Kashyap regarding blk_mq_queue_tag_busy_iter() Looks fine: Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx> Thanks, Ming
