From: Pavel Begunkov <asml.silence@gmail.com>
Date: Fri, 29 Nov 2019 00:11:53 +0300
Subject: [PATCH] blk-mq: optimise rq sort function
References: bsc#1175995,jsc#SLE-15608
Git-commit: 7d30a621028a22a9e8fbae5c5d8dc455869e4999
Patch-mainline: v5.6-rc1
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>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
block/blk-mq.c | 12 ++++--------
1 file changed, 4 insertions(+), 8 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 13cdaf9932a6..38026a66c812 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1672,14 +1672,10 @@ 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);
}
--
2.16.4