reduce mballoc stack usage with noinline

mballoc.c is a whole lot of static functions, which gcc seems to really like to inline.

With the changes below, on x86, I can at least get from:

432 ext4_mb_new_blocks
240 ext4_mb_free_blocks
208 ext4_mb_discard_group_preallocations
188 ext4_mb_seq_groups_show
164 ext4_mb_init_cache
152 ext4_mb_release_inode_pa
136 ext4_mb_seq_history_show
...

to

220 ext4_mb_free_blocks
188 ext4_mb_seq_groups_show
176 ext4_mb_regular_allocator
164 ext4_mb_init_cache
156 ext4_mb_new_blocks
152 ext4_mb_release_inode_pa
136 ext4_mb_seq_history_show
124 ext4_mb_release_group_pa
...

which still has some big functions in there, but not 432 bytes!

I wonder if a zone would make sense for struct ext4_allocation_context, it's 108 bytes by itself.

I haven't honestly done any investigation of any performance impact of the noinlines; FWIW xfs just took control of inlining, and marked almost every non-trivial function as noinline, (although the xfs situation was a little more dire) and I don't think they had any noticeable performance impact.

Signed-off-by Eric Sandeen <[email protected]>

---

Index: linux-2.6.24-git9/fs/ext4/mballoc.c
===================================================================

fs/ext4/mballoc.c +14 -15

@@ -1146,7 +1146,7 @@ out:
 	return err;
 }
 
-static int ext4_mb_load_buddy(struct super_block *sb, ext4_group_t group,
+static noinline int ext4_mb_load_buddy(struct super_block *sb, ext4_group_t group,
 		struct ext4_buddy *e4b)
 {
 	struct ext4_sb_info *sbi = EXT4_SB(sb);

@@ -1926,7 +1926,7 @@ static int ext4_mb_good_group(struct ext
 	return 0;
 }
 
-static int ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
+static noinline int ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
 {
 	ext4_group_t group;
 	ext4_group_t i;

@@ -2433,7 +2433,7 @@ static void ext4_mb_history_init(struct 
 	/* if we can't allocate history, then we simple won't use it */
 }
 
-static void ext4_mb_store_history(struct ext4_allocation_context *ac)
+static noinline void ext4_mb_store_history(struct ext4_allocation_context *ac)
 {
 	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
 	struct ext4_mb_history h;

@@ -2769,7 +2769,7 @@ int ext4_mb_release(struct super_block *
 	return 0;
 }
 
-static void ext4_mb_free_committed_blocks(struct super_block *sb)
+static noinline void ext4_mb_free_committed_blocks(struct super_block *sb)
 {
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
 	int err;

@@ -2982,7 +2982,7 @@ void exit_ext4_mballoc(void)
  * Check quota and mark choosed space (ac->ac_b_ex) non-free in bitmaps
  * Returns 0 if success or error code
  */
-static int ext4_mb_mark_diskspace_used(struct ext4_allocation_context *ac,
+static noinline int ext4_mb_mark_diskspace_used(struct ext4_allocation_context *ac,
 				handle_t *handle)
 {
 	struct buffer_head *bitmap_bh = NULL;

@@ -3099,7 +3099,7 @@ static void ext4_mb_normalize_group_requ
  * Normalization means making request better in terms of
  * size and alignment
  */
-static void ext4_mb_normalize_request(struct ext4_allocation_context *ac,
+static noinline void ext4_mb_normalize_request(struct ext4_allocation_context *ac,
 				struct ext4_allocation_request *ar)
 {
 	int bsbits, max;

@@ -3368,7 +3368,7 @@ static void ext4_mb_use_group_pa(struct 
 /*
  * search goal blocks in preallocated space
  */
-static int ext4_mb_use_preallocated(struct ext4_allocation_context *ac)
+static noinline int ext4_mb_use_preallocated(struct ext4_allocation_context *ac)
 {
 	struct ext4_inode_info *ei = EXT4_I(ac->ac_inode);
 	struct ext4_locality_group *lg;

@@ -3535,7 +3535,7 @@ static void ext4_mb_put_pa(struct ext4_a
 /*
  * creates new preallocated space for given inode
  */
-static int ext4_mb_new_inode_pa(struct ext4_allocation_context *ac)
+static noinline int ext4_mb_new_inode_pa(struct ext4_allocation_context *ac)
 {
 	struct super_block *sb = ac->ac_sb;
 	struct ext4_prealloc_space *pa;

@@ -3622,7 +3622,7 @@ static int ext4_mb_new_inode_pa(struct e
 /*
  * creates new preallocated space for locality group inodes belongs to
  */
-static int ext4_mb_new_group_pa(struct ext4_allocation_context *ac)
+static noinline int ext4_mb_new_group_pa(struct ext4_allocation_context *ac)
 {
 	struct super_block *sb = ac->ac_sb;
 	struct ext4_locality_group *lg;

@@ -3695,7 +3695,7 @@ static int ext4_mb_new_preallocation(str
  * the caller MUST hold group/inode locks.
  * TODO: optimize the case when there are no in-core structures yet
  */
-static int ext4_mb_release_inode_pa(struct ext4_buddy *e4b,
+static noinline int ext4_mb_release_inode_pa(struct ext4_buddy *e4b,
 				struct buffer_head *bitmap_bh,
 				struct ext4_prealloc_space *pa)
 {

@@ -3755,7 +3755,7 @@ static int ext4_mb_release_inode_pa(stru
 	return err;
 }
 
-static int ext4_mb_release_group_pa(struct ext4_buddy *e4b,
+static noinline int ext4_mb_release_group_pa(struct ext4_buddy *e4b,
 				struct ext4_prealloc_space *pa)
 {
 	struct ext4_allocation_context ac;

@@ -3791,7 +3791,7 @@ static int ext4_mb_release_group_pa(stru
  * - how many do we discard
  *   1) how many requested
  */
-static int ext4_mb_discard_group_preallocations(struct super_block *sb,
+static noinline int ext4_mb_discard_group_preallocations(struct super_block *sb,
 					ext4_group_t group, int needed)
 {
 	struct ext4_group_info *grp = ext4_get_group_info(sb, group);

@@ -4113,7 +4113,7 @@ static void ext4_mb_group_or_file(struct
 	mutex_lock(&ac->ac_lg->lg_mutex);
 }
 
-static int ext4_mb_initialize_context(struct ext4_allocation_context *ac,
+static noinline int ext4_mb_initialize_context(struct ext4_allocation_context *ac,
 				struct ext4_allocation_request *ar)
 {
 	struct super_block *sb = ar->inode->i_sb;

@@ -4337,7 +4337,7 @@ static void ext4_mb_poll_new_transaction
 	ext4_mb_free_committed_blocks(sb);
 }
 
-static int ext4_mb_free_metadata(handle_t *handle, struct ext4_buddy *e4b,
+static noinline int ext4_mb_free_metadata(handle_t *handle, struct ext4_buddy *e4b,
 			  ext4_group_t group, ext4_grpblk_t block, int count)
 {
 	struct ext4_group_info *db = e4b->bd_info;
 
-

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