dm: eliminate some holes data structures

Eliminate a 4-byte hole in 'struct dm_io_memory' by moving 'offset' above the 'ptr' to which it applies (size reduced from 24 to 16 bytes). And by association, 1-4 byte hole is eliminated in 'struct dm_io_request' (size reduced from 56 to 48 bytes). Eliminate all 6 4-byte holes and 1 cache-line in 'struct dm_snapshot' (size reduced from 392 to 368 bytes). Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>

dm: eliminate some holes data structures
Eliminate a 4-byte hole in 'struct dm_io_memory' by moving 'offset' above the 'ptr' to which it applies (size reduced from 24 to 16 bytes). And by association, 1-4 byte hole is eliminated in 'struct dm_io_request' (size reduced from 56 to 48 bytes). Eliminate all 6 4-byte holes and 1 cache-line in 'struct dm_snapshot' (size reduced from 392 to 368 bytes). Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Mike Snitzer · Alasdair G Kergon
1 parent 3abf85b5b5
Showing 2 changed files with 15 additions and 15 deletions Side-by-side Diff
drivers/md/dm-snap.c
include/linux/dm-io.h
@@ -83,10 +83,10 @@
 	/* Whether or not owning mapped_device is suspended */
 	int suspended;
  
-	mempool_t *pending_pool;
-
 	atomic_t pending_exceptions_count;
  
+	mempool_t *pending_pool;
+
 	struct dm_exception_table pending;
 	struct dm_exception_table complete;
  
@@ -96,6 +96,11 @@
 	 */
 	spinlock_t pe_lock;
  
+	/* Chunks with outstanding reads */
+	spinlock_t tracked_chunk_lock;
+	mempool_t *tracked_chunk_pool;
+	struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE];
+
 	/* The on disk metadata handler */
 	struct dm_exception_store *store;
  
  
@@ -105,11 +110,13 @@
 	struct bio_list queued_bios;
 	struct work_struct queued_bios_work;
  
-	/* Chunks with outstanding reads */
-	mempool_t *tracked_chunk_pool;
-	spinlock_t tracked_chunk_lock;
-	struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE];
+	/* Wait for events based on state_bits */
+	unsigned long state_bits;
  
+	/* Range of chunks currently being merged. */
+	chunk_t first_merging_chunk;
+	int num_merging_chunks;
+
 	/*
 	 * The merge operation failed if this flag is set.
 	 * Failure modes are handled as follows:
@@ -124,13 +131,6 @@
 	 *	=> stop merging; set merge_failed; process I/O normally.
 	 */
 	int merge_failed;
-
-	/* Wait for events based on state_bits */
-	unsigned long state_bits;
-
-	/* Range of chunks currently being merged. */
-	chunk_t first_merging_chunk;
-	int num_merging_chunks;
  
 	/*
 	 * Incoming bios that overlap with chunks being merged must wait
@@ -37,14 +37,14 @@
 struct dm_io_memory {
 	enum dm_io_mem_type type;
  
+	unsigned offset;
+
 	union {
 		struct page_list *pl;
 		struct bio_vec *bvec;
 		void *vma;
 		void *addr;
 	} ptr;
-
-	unsigned offset;
 };
  
 struct dm_io_notify {
...	...	@@ -83,10 +83,10 @@
83	83	/* Whether or not owning mapped_device is suspended */
84	84	int suspended;
85	85
86		- mempool_t *pending_pool;
87		-
88	86	atomic_t pending_exceptions_count;
89	87
	88	+ mempool_t *pending_pool;
	89	+
90	90	struct dm_exception_table pending;
91	91	struct dm_exception_table complete;
92	92
...	...	@@ -96,6 +96,11 @@
96	96	*/
97	97	spinlock_t pe_lock;
98	98
	99	+ /* Chunks with outstanding reads */
	100	+ spinlock_t tracked_chunk_lock;
	101	+ mempool_t *tracked_chunk_pool;
	102	+ struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE];
	103	+
99	104	/* The on disk metadata handler */
100	105	struct dm_exception_store *store;
101	106
102	107
...	...	@@ -105,11 +110,13 @@
105	110	struct bio_list queued_bios;
106	111	struct work_struct queued_bios_work;
107	112
108		- /* Chunks with outstanding reads */
109		- mempool_t *tracked_chunk_pool;
110		- spinlock_t tracked_chunk_lock;
111		- struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE];
	113	+ /* Wait for events based on state_bits */
	114	+ unsigned long state_bits;
112	115
	116	+ /* Range of chunks currently being merged. */
	117	+ chunk_t first_merging_chunk;
	118	+ int num_merging_chunks;
	119	+
113	120	/*
114	121	* The merge operation failed if this flag is set.
115	122	* Failure modes are handled as follows:
...	...	@@ -124,13 +131,6 @@
124	131	* => stop merging; set merge_failed; process I/O normally.
125	132	*/
126	133	int merge_failed;
127		-
128		- /* Wait for events based on state_bits */
129		- unsigned long state_bits;
130		-
131		- /* Range of chunks currently being merged. */
132		- chunk_t first_merging_chunk;
133		- int num_merging_chunks;
134	134
135	135	/*
136	136	* Incoming bios that overlap with chunks being merged must wait
...	...	@@ -37,14 +37,14 @@
37	37	struct dm_io_memory {
38	38	enum dm_io_mem_type type;
39	39
	40	+ unsigned offset;
	41	+
40	42	union {
41	43	struct page_list *pl;
42	44	struct bio_vec *bvec;
43	45	void *vma;
44	46	void *addr;
45	47	} ptr;
46		-
47		- unsigned offset;
48	48	};
49	49
50	50	struct dm_io_notify {