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ext4: use percpu counter for extent cache count

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Use a percpu counter rather than atomic types for shrinker accounting.
There's no need for ultimate accuracy in the shrinker, so this
should come a little more cheaply.  The percpu struct is somewhat
large, but there was a big gap before the cache-aligned
s_es_lru_lock anyway, and it fits nicely in there.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Theodore Ts'o 2013-03-02 10:27:46 -05:00
parent 246307745c
commit 1ac6466f25
3 changed files with 10 additions and 5 deletions
Download patch file Download diff file Expand all files Collapse all files

8
fs/ext4/extents_status.c
View file

@ -305,7 +305,7 @@ ext4_es_alloc_extent(struct inode *inode, ext4_lblk_t lblk, ext4_lblk_t len,
*/
if (!ext4_es_is_delayed(es)) {
EXT4_I(inode)->i_es_lru_nr++;
atomic_inc(&EXT4_SB(inode->i_sb)->s_extent_cache_cnt);
percpu_counter_inc(&EXT4_SB(inode->i_sb)->s_extent_cache_cnt);
}
return es;
@ -317,7 +317,7 @@ static void ext4_es_free_extent(struct inode *inode, struct extent_status *es)
if (!ext4_es_is_delayed(es)) {
BUG_ON(EXT4_I(inode)->i_es_lru_nr == 0);
EXT4_I(inode)->i_es_lru_nr--;
atomic_dec(&EXT4_SB(inode->i_sb)->s_extent_cache_cnt);
percpu_counter_dec(&EXT4_SB(inode->i_sb)->s_extent_cache_cnt);
}
kmem_cache_free(ext4_es_cachep, es);
@ -678,7 +678,7 @@ static int ext4_es_shrink(struct shrinker *shrink, struct shrink_control *sc)
int nr_to_scan = sc->nr_to_scan;
int ret, nr_shrunk = 0;
ret = atomic_read(&sbi->s_extent_cache_cnt);
ret = percpu_counter_read_positive(&sbi->s_extent_cache_cnt);
trace_ext4_es_shrink_enter(sbi->s_sb, nr_to_scan, ret);
if (!nr_to_scan)
@ -711,7 +711,7 @@ static int ext4_es_shrink(struct shrinker *shrink, struct shrink_control *sc)
list_splice_tail(&scanned, &sbi->s_es_lru);
spin_unlock(&sbi->s_es_lru_lock);
ret = atomic_read(&sbi->s_extent_cache_cnt);
ret = percpu_counter_read_positive(&sbi->s_extent_cache_cnt);
trace_ext4_es_shrink_exit(sbi->s_sb, nr_shrunk, ret);
return ret;
}