ext4: reduce mballoc stack usage with noinline From: Eric Sandeen 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 Signed-off-by: Mingming Cao Signed-off-by: "Theodore Ts'o" --- fs/ext4/mballoc.c | 36 +++++++++++++++++++++--------------- 1 file changed, 21 insertions(+), 15 deletions(-) Index: linux-2.6.25-rc3/fs/ext4/mballoc.c =================================================================== --- linux-2.6.25-rc3.orig/fs/ext4/mballoc.c 2008-03-03 15:52:01.000000000 -0800 +++ linux-2.6.25-rc3/fs/ext4/mballoc.c 2008-03-03 15:52:16.000000000 -0800 @@ -1168,8 +1168,9 @@ out: return err; } -static int ext4_mb_load_buddy(struct super_block *sb, ext4_group_t group, - struct ext4_buddy *e4b) +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); struct inode *inode = sbi->s_buddy_cache; @@ -1965,7 +1966,8 @@ 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; @@ -2472,7 +2474,7 @@ 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; @@ -2808,7 +2810,7 @@ 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; @@ -3029,7 +3031,8 @@ 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; @@ -3146,7 +3149,8 @@ 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; @@ -3412,7 +3416,7 @@ 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; @@ -3579,7 +3583,7 @@ 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; @@ -3666,7 +3670,7 @@ 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; @@ -3739,7 +3743,7 @@ 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) { @@ -3811,7 +3815,7 @@ 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; @@ -3853,7 +3857,7 @@ 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); @@ -4175,7 +4179,8 @@ 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; @@ -4406,7 +4411,8 @@ 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;