Commit 0864fe09 authored Dec 20, 2017 by Jens Axboe

null_blk: unalign call_single_data



Commit 966a9671 randomly added alignment to this structure, but
it's actually detrimental to performance of null_blk. Test case:

Running on both the home and remote node shows a ~5% degradation
in performance.

While in there, move blk_status_t to the hole after the integer tag
in the nullb_cmd structure. After this patch, we shrink the size
from 192 to 152 bytes.

Fixes: 966a9671 ("smp: Avoid using two cache lines for struct call_single_data")
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 4ccafe03

drivers/block/null_blk.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -35,13 +35,13 @@ static inline u64 mb_per_tick(int mbps)
		struct nullb_cmd {
		struct list_head list;
		struct llist_node ll_list;
		call_single_data_t csd;
		struct __call_single_data csd;
		struct request *rq;
		struct bio *bio;
		unsigned int tag;
		blk_status_t error;
		struct nullb_queue *nq;
		struct hrtimer timer;
		blk_status_t error;
		};

		struct nullb_queue {