Commit 966a967116e6 randomly added alignment to this structure, but
it's actually detrimental to performance of null_blk. Test case:
# modprobe null_blk queue_mode=1 irqmode=1 home_node={0,1}
# echo noop > /sys/block/nullb0/queue/scheduler
# fio --name=csd --filename=/dev/nullb0 --numjobs=8 --direct=1 --rw=randread --norandommap --cpus_allowed=$(cat /sys/devices/system/node/node0/cpulist) --group_reporting=1
Running on both the home and remote node shows a ~5% degradation
in performance.
Fixes: 966a967116e69 ("smp: Avoid using two cache lines for struct call_single_data")
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
diff --git a/drivers/block/null_blk.c b/drivers/block/null_blk.c
index ccb9975a97fa..8c6912dd5142 100644
--- a/drivers/block/null_blk.c
+++ b/drivers/block/null_blk.c
@@ -35,7 +35,7 @@ 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;
--
Jens Axboe
