diff options
| author | Theodore Ts'o <tytso@mit.edu> | 2011-09-09 19:02:51 -0400 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2011-09-09 19:02:51 -0400 |
| commit | 27baebb849d46d901e756e6502b0a65a62e43771 (patch) | |
| tree | ed72a295f62656beb29038358d99902b55b3438f | |
| parent | f975d6bcc7a698a10cc755115e27d3612dcfe322 (diff) | |
ext4: tune mballoc's default group prealloc size for bigalloc file systems
The default group preallocation size had been previously set to 512
blocks/clusters, regardless of the block/cluster size. This is
probably too big for large cluster sizes. So adjust the default so
that it is 2 megabytes or 32 clusters, whichever is larger.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
| -rw-r--r-- | fs/ext4/mballoc.c | 18 |
1 files changed, 16 insertions, 2 deletions
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index f8e37cf2c2dd..63dd56703342 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -126,7 +126,8 @@ * list. In case of inode preallocation we follow a list of heuristics * based on file size. This can be found in ext4_mb_normalize_request. If * we are doing a group prealloc we try to normalize the request to - * sbi->s_mb_group_prealloc. Default value of s_mb_group_prealloc is + * sbi->s_mb_group_prealloc. The default value of s_mb_group_prealloc is + * dependent on the cluster size; for non-bigalloc file systems, it is * 512 blocks. This can be tuned via * /sys/fs/ext4/<partition>/mb_group_prealloc. The value is represented in * terms of number of blocks. If we have mounted the file system with -O @@ -2473,7 +2474,20 @@ int ext4_mb_init(struct super_block *sb, int needs_recovery) sbi->s_mb_stats = MB_DEFAULT_STATS; sbi->s_mb_stream_request = MB_DEFAULT_STREAM_THRESHOLD; sbi->s_mb_order2_reqs = MB_DEFAULT_ORDER2_REQS; - sbi->s_mb_group_prealloc = MB_DEFAULT_GROUP_PREALLOC; + /* + * The default group preallocation is 512, which for 4k block + * sizes translates to 2 megabytes. However for bigalloc file + * systems, this is probably too big (i.e, if the cluster size + * is 1 megabyte, then group preallocation size becomes half a + * gigabyte!). As a default, we will keep a two megabyte + * group pralloc size for cluster sizes up to 64k, and after + * that, we will force a minimum group preallocation size of + * 32 clusters. This translates to 8 megs when the cluster + * size is 256k, and 32 megs when the cluster size is 1 meg, + * which seems reasonable as a default. + */ + sbi->s_mb_group_prealloc = max(MB_DEFAULT_GROUP_PREALLOC >> + sbi->s_cluster_bits, 32); /* * If there is a s_stripe > 1, then we set the s_mb_group_prealloc * to the lowest multiple of s_stripe which is bigger than |