@@ -473,6 +473,7 @@ enum hctx_type {
/**
* struct blk_mq_tag_set - tag set that can be shared between request queues
+ * @ops: Pointers to functions that implement block driver behavior.
* @map: One or more ctx -> hctx mappings. One map exists for each
* hardware queue type (enum hctx_type) that the driver wishes
* to support. There are no restrictions on maps being of the
@@ -480,7 +481,6 @@ enum hctx_type {
* types.
* @nr_maps: Number of elements in the @map array. A number in the range
* [1, HCTX_MAX_TYPES].
- * @ops: Pointers to functions that implement block driver behavior.
* @nr_hw_queues: Number of hardware queues supported by the block driver that
* owns this data structure.
* @queue_depth: Number of tags per hardware queue, reserved tags included.
@@ -505,9 +505,9 @@ enum hctx_type {
* (BLK_MQ_F_BLOCKING).
*/
struct blk_mq_tag_set {
+ const struct blk_mq_ops *ops;
struct blk_mq_queue_map map[HCTX_MAX_TYPES];
unsigned int nr_maps;
- const struct blk_mq_ops *ops;
unsigned int nr_hw_queues;
unsigned int queue_depth;
unsigned int reserved_tags;
Group some variables based on their sizes to reduce hole and avoid padding. On x86_64, this shrinks the size of 'struct blk_mq_tag_set' from 304 to 296 bytes. Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr> --- Using pahole Before: ====== struct blk_mq_tag_set { struct blk_mq_queue_map map[3]; /* 0 48 */ unsigned int nr_maps; /* 48 4 */ /* XXX 4 bytes hole, try to pack */ const struct blk_mq_ops * ops; /* 56 8 */ /* --- cacheline 1 boundary (64 bytes) --- */ unsigned int nr_hw_queues; /* 64 4 */ unsigned int queue_depth; /* 68 4 */ unsigned int reserved_tags; /* 72 4 */ unsigned int cmd_size; /* 76 4 */ int numa_node; /* 80 4 */ unsigned int timeout; /* 84 4 */ unsigned int flags; /* 88 4 */ /* XXX 4 bytes hole, try to pack */ void * driver_data; /* 96 8 */ struct blk_mq_tags * * tags; /* 104 8 */ struct blk_mq_tags * shared_tags; /* 112 8 */ struct mutex tag_list_lock; /* 120 160 */ /* --- cacheline 4 boundary (256 bytes) was 24 bytes ago --- */ struct list_head tag_list; /* 280 16 */ struct srcu_struct * srcu; /* 296 8 */ /* size: 304, cachelines: 5, members: 16 */ /* sum members: 296, holes: 2, sum holes: 8 */ /* last cacheline: 48 bytes */ }; After: ===== struct blk_mq_tag_set { const struct blk_mq_ops * ops; /* 0 8 */ struct blk_mq_queue_map map[3]; /* 8 48 */ unsigned int nr_maps; /* 56 4 */ unsigned int nr_hw_queues; /* 60 4 */ /* --- cacheline 1 boundary (64 bytes) --- */ unsigned int queue_depth; /* 64 4 */ unsigned int reserved_tags; /* 68 4 */ unsigned int cmd_size; /* 72 4 */ int numa_node; /* 76 4 */ unsigned int timeout; /* 80 4 */ unsigned int flags; /* 84 4 */ void * driver_data; /* 88 8 */ struct blk_mq_tags * * tags; /* 96 8 */ struct blk_mq_tags * shared_tags; /* 104 8 */ struct mutex tag_list_lock; /* 112 160 */ /* --- cacheline 4 boundary (256 bytes) was 16 bytes ago --- */ struct list_head tag_list; /* 272 16 */ struct srcu_struct * srcu; /* 288 8 */ /* size: 296, cachelines: 5, members: 16 */ /* last cacheline: 40 bytes */ }; --- include/linux/blk-mq.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)