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null_blk: unalign call_single_data

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Commit 966a967116 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: 966a967116 ("smp: Avoid using two cache lines for struct call_single_data")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2017-12-20 13:14:42 -07:00
parent 4ccafe0320
commit 0864fe09ab
1 changed files with 2 additions and 2 deletions
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4
drivers/block/null_blk.c
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@ -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 {