blk-mq: optimise rq sort function (7d30a621) · Commits · 戴 / test

Check "!=" in multi-layer comparisons. The same memory usage, fewer instructions, and 2 from 4 jumps are replaced with SETcc. Note, that list_sort() doesn't differ 0 and <0. Reviewed-by:

Nikolay Borisov <nborisov@suse.com> Signed-off-by:

Pavel Begunkov <asml.silence@gmail.com> Signed-off-by:

Jens Axboe <axboe@kernel.dk>

block/blk-mq.c

+4 −8

Original line number	Diff line number	Diff line
		@@ -1668,14 +1668,10 @@ static int plug_rq_cmp(void priv, struct list_head a, struct list_head *b)
		struct request *rqa = container_of(a, struct request, queuelist);
		struct request *rqb = container_of(b, struct request, queuelist);

		if (rqa->mq_ctx < rqb->mq_ctx)
		return -1;
		else if (rqa->mq_ctx > rqb->mq_ctx)
		return 1;
		else if (rqa->mq_hctx < rqb->mq_hctx)
		return -1;
		else if (rqa->mq_hctx > rqb->mq_hctx)
		return 1;
		if (rqa->mq_ctx != rqb->mq_ctx)
		return rqa->mq_ctx > rqb->mq_ctx;
		if (rqa->mq_hctx != rqb->mq_hctx)
		return rqa->mq_hctx > rqb->mq_hctx;

		return blk_rq_pos(rqa) > blk_rq_pos(rqb);
		}

Admin message