diff options
| author | David Sterba <dsterba@suse.com> | 2019-10-24 19:31:10 +0200 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2019-10-25 14:12:50 -0600 |
| commit | 993e4cdebb5a53bc87f21cdd34d1dc42225de43d (patch) | |
| tree | f43b27d721fd2d6a97a38a08942a5bdecfd43136 | |
| parent | f7e76dbc24df695f1b8e88ed3201be22215ec969 (diff) | |
block: reorder bio::__bi_remaining for better packing
Simple reordering of __bi_remaining can reduce bio size by 8 bytes that
are now wasted on padding (measured on x86_64):
struct bio {
struct bio * bi_next; /* 0 8 */
struct gendisk * bi_disk; /* 8 8 */
unsigned int bi_opf; /* 16 4 */
short unsigned int bi_flags; /* 20 2 */
short unsigned int bi_ioprio; /* 22 2 */
short unsigned int bi_write_hint; /* 24 2 */
blk_status_t bi_status; /* 26 1 */
u8 bi_partno; /* 27 1 */
/* XXX 4 bytes hole, try to pack */
struct bvec_iter bi_iter; /* 32 24 */
/* XXX last struct has 4 bytes of padding */
atomic_t __bi_remaining; /* 56 4 */
/* XXX 4 bytes hole, try to pack */
[...]
/* size: 104, cachelines: 2, members: 19 */
/* sum members: 96, holes: 2, sum holes: 8 */
/* paddings: 1, sum paddings: 4 */
/* last cacheline: 40 bytes */
};
Now becomes:
struct bio {
struct bio * bi_next; /* 0 8 */
struct gendisk * bi_disk; /* 8 8 */
unsigned int bi_opf; /* 16 4 */
short unsigned int bi_flags; /* 20 2 */
short unsigned int bi_ioprio; /* 22 2 */
short unsigned int bi_write_hint; /* 24 2 */
blk_status_t bi_status; /* 26 1 */
u8 bi_partno; /* 27 1 */
atomic_t __bi_remaining; /* 28 4 */
struct bvec_iter bi_iter; /* 32 24 */
/* XXX last struct has 4 bytes of padding */
[...]
/* size: 96, cachelines: 2, members: 19 */
/* paddings: 1, sum paddings: 4 */
/* last cacheline: 32 bytes */
};
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | include/linux/blk_types.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h index d688b96d1d63..1e7eeec16458 100644 --- a/include/linux/blk_types.h +++ b/include/linux/blk_types.h @@ -153,10 +153,10 @@ struct bio { unsigned short bi_write_hint; blk_status_t bi_status; u8 bi_partno; + atomic_t __bi_remaining; struct bvec_iter bi_iter; - atomic_t __bi_remaining; bio_end_io_t *bi_end_io; void *bi_private; |