Commit 089ceecc authored by Eric Sandeen's avatar Eric Sandeen Committed by Theodore Ts'o
Browse files

ext4: mark several more functions in mballoc.c as noinline 



Ted noticed a stack-deep callchain through
writepages->ext4_mb_regular_allocator->ext4_mb_init_cache->submit_bh ...

With all the static functions in mballoc.c, gcc helpfully
inlines for us, and we get something like this:

ext4_mb_regular_allocator	(232 bytes stack)
	ext4_mb_init_cache	(232 bytes stack)
		submit_bh	(starts 464 deeper)

the 2 ext4 functions here get several others inlined; by telling
gcc not to inline them, we can save stack space for when we
head off into submit_bh land and associated block layer callchains.
The following noinlined functions are only called once, so this
won't impact any other callchains:

ext4_mb_regular_allocator 			(104) (was 232)
	ext4_mb_find_by_goal			 (56) (noinlined)
	ext4_mb_init_group			 (24) (noinlined)
		ext4_mb_init_cache		(136) (was 232)
			ext4_mb_generate_buddy	 (88) (noinlined)
			ext4_mb_generate_from_pa (40) (noinlined)
			submit_bh
	ext4_mb_simple_scan_group		 (24) (noinlined)
	ext4_mb_scan_aligned			 (56) (noinlined)
	ext4_mb_complex_scan_group		 (40) (noinlined)
	ext4_mb_try_best_found			 (24) (noinlined)

now when we head off into submit_bh() we're only 264 bytes deeper
in stack than when we entered ext4_mb_regular_allocator()
(vs. 464 bytes before).  Every 200 bytes helps.  :)

Signed-off-by: default avatarEric Sandeen <sandeen@redhat.com>
Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent f4a01017

fs/ext4/mballoc.c

+16 −8
Original line number Diff line number Diff line
@@ -657,7 +657,8 @@ static void ext4_mb_mark_free_simple(struct super_block *sb, 
	}

}



static void ext4_mb_generate_buddy(struct super_block *sb,

static noinline_for_stack

void ext4_mb_generate_buddy(struct super_block *sb,

				void *buddy, void *bitmap, ext4_group_t group)

{

	struct ext4_group_info *grp = ext4_get_group_info(sb, group);
@@ -1480,7 +1481,8 @@ static void ext4_mb_measure_extent(struct ext4_allocation_context *ac, 
	ext4_mb_check_limits(ac, e4b, 0);

}



static int ext4_mb_try_best_found(struct ext4_allocation_context *ac,

static noinline_for_stack

int ext4_mb_try_best_found(struct ext4_allocation_context *ac,

					struct ext4_buddy *e4b)

{

	struct ext4_free_extent ex = ac->ac_b_ex;
@@ -1507,7 +1509,8 @@ static int ext4_mb_try_best_found(struct ext4_allocation_context *ac, 
	return 0;

}



static int ext4_mb_find_by_goal(struct ext4_allocation_context *ac,

static noinline_for_stack

int ext4_mb_find_by_goal(struct ext4_allocation_context *ac,

				struct ext4_buddy *e4b)

{

	ext4_group_t group = ac->ac_g_ex.fe_group;
@@ -1566,7 +1569,8 @@ static int ext4_mb_find_by_goal(struct ext4_allocation_context *ac, 
 * The routine scans buddy structures (not bitmap!) from given order

 * to max order and tries to find big enough chunk to satisfy the req

 */

static void ext4_mb_simple_scan_group(struct ext4_allocation_context *ac,

static noinline_for_stack

void ext4_mb_simple_scan_group(struct ext4_allocation_context *ac,

					struct ext4_buddy *e4b)

{

	struct super_block *sb = ac->ac_sb;
@@ -1609,7 +1613,8 @@ static void ext4_mb_simple_scan_group(struct ext4_allocation_context *ac, 
 * In order to optimize scanning, caller must pass number of

 * free blocks in the group, so the routine can know upper limit.

 */

static void ext4_mb_complex_scan_group(struct ext4_allocation_context *ac,

static noinline_for_stack

void ext4_mb_complex_scan_group(struct ext4_allocation_context *ac,

					struct ext4_buddy *e4b)

{

	struct super_block *sb = ac->ac_sb;
@@ -1668,7 +1673,8 @@ static void ext4_mb_complex_scan_group(struct ext4_allocation_context *ac, 
 * we try to find stripe-aligned chunks for stripe-size requests

 * XXX should do so at least for multiples of stripe size as well

 */

static void ext4_mb_scan_aligned(struct ext4_allocation_context *ac,

static noinline_for_stack

void ext4_mb_scan_aligned(struct ext4_allocation_context *ac,

				 struct ext4_buddy *e4b)

{

	struct super_block *sb = ac->ac_sb;
@@ -1831,7 +1837,8 @@ void ext4_mb_put_buddy_cache_lock(struct super_block *sb, 


}



static int ext4_mb_init_group(struct super_block *sb, ext4_group_t group)

static noinline_for_stack

int ext4_mb_init_group(struct super_block *sb, ext4_group_t group)

{



	int ret;
@@ -3457,7 +3464,8 @@ static void ext4_mb_generate_from_freelist(struct super_block *sb, void *bitmap, 
 * used in in-core bitmap. buddy must be generated from this bitmap

 * Need to be called with ext4 group lock held

 */

static void ext4_mb_generate_from_pa(struct super_block *sb, void *bitmap,

static noinline_for_stack

void ext4_mb_generate_from_pa(struct super_block *sb, void *bitmap,

					ext4_group_t group)

{

	struct ext4_group_info *grp = ext4_get_group_info(sb, group);

CRA Git | Maintained and supported by SUSTech CRA and CCSE