Viewing: ext4-optimize-the-ext4_mb_good_group.patch
commit dddcd2f9ebdeca9fbd36526e950bbcd0f7c1765f
Author: brookxu <brookxu.cn@gmail.com>
AuthorDate: Fri Aug 7 22:01:39 2020 +0800
ext4: optimize the implementation of ext4_mb_good_group()
It might be better to adjust the code in two places:
1. Determine whether grp is currupt or not should be placed first.
2. (cr<=2 && free <ac->ac_g_ex.fe_len)should may belong to the crx
strategy, and it may be more appropriate to put it in the
subsequent switch statement block. For cr1, cr2, the conditions
in switch potentially realize the above judgment. For cr0, we
should add (free <ac->ac_g_ex.fe_len) judgment, and then delete
(free / fragments) >= ac->ac_g_ex.fe_len), because cr0 returns
true by default.
Signed-off-by: Chunguang Xu <brookxu@tencent.com>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Reviewed-by: Ritesh Harjani <riteshh@linux.ibm.com>
Link: https://lore.kernel.org/r/e20b2d8f-1154-adb7-3831-a9e11ba842e9@gmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
---
Index: linux-stage/fs/ext4/mballoc.c
===================================================================
--- linux-stage.orig/fs/ext4/mballoc.c
+++ linux-stage/fs/ext4/mballoc.c
@@ -2135,13 +2135,11 @@ static bool ext4_mb_good_group(struct ex
BUG_ON(cr < 0 || cr >= 4);
- free = grp->bb_free;
- if (free == 0)
- return false;
- if (cr <= 2 && free < ac->ac_g_ex.fe_len)
+ if (unlikely(EXT4_MB_GRP_BBITMAP_CORRUPT(grp)))
return false;
- if (unlikely(EXT4_MB_GRP_BBITMAP_CORRUPT(grp)))
+ free = grp->bb_free;
+ if (free == 0)
return false;
fragments = grp->bb_fragments;
@@ -2158,8 +2156,10 @@ static bool ext4_mb_good_group(struct ex
((group % flex_size) == 0))
return false;
- if ((ac->ac_2order > ac->ac_sb->s_blocksize_bits+1) ||
- (free / fragments) >= ac->ac_g_ex.fe_len)
+ if (free < ac->ac_g_ex.fe_len)
+ return false;
+
+ if (ac->ac_2order > ac->ac_sb->s_blocksize_bits+1)
return true;
if (grp->bb_largest_free_order < ac->ac_2order)
