blk-mq: complete polled requests directly (6aab1da6) · Commits · 戴 / test

Even for single queue devices there is no point in offloading a polled completion to the softirq, given that blk_mq_force_complete_rq is called from the polling thread in that case and thus there are no starvation issues. Reviewed-by:

Daniel Wagner <dwagner@suse.de> Signed-off-by:

Christoph Hellwig <hch@lst.de> Signed-off-by:

Jens Axboe <axboe@kernel.dk>

block/blk-mq.c

+11 −6

Original line number	Diff line number	Diff line
		@@ -703,6 +703,16 @@ void blk_mq_force_complete_rq(struct request *rq)
		int cpu;

		WRITE_ONCE(rq->state, MQ_RQ_COMPLETE);

		/*
		* For a polled request, always complete locallly, it's pointless
		* to redirect the completion.
		*/
		if (rq->cmd_flags & REQ_HIPRI) {
		q->mq_ops->complete(rq);
		return;
		}

		/*
		* Most of single queue controllers, there is only one irq vector
		* for handling IO completion, and the only irq's affinity is set
		@@ -717,12 +727,7 @@ void blk_mq_force_complete_rq(struct request *rq)
		return;
		}

		/*
		* For a polled request, always complete locallly, it's pointless
		* to redirect the completion.
		*/
		if ((rq->cmd_flags & REQ_HIPRI) \|\|
		!test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags)) {
		if (!test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags)) {
		q->mq_ops->complete(rq);
		return;
		}

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