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ext4: use percpu counter for extent cache count

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>
master
Theodore Ts'o 9 years ago
parent
commit
1ac6466f25
  1. 2
      fs/ext4/ext4.h
  2. 8
      fs/ext4/extents_status.c
  3. 5
      fs/ext4/super.c

2
fs/ext4/ext4.h

@ -1268,7 +1268,6 @@ struct ext4_sb_info {
atomic_t s_mb_preallocated;
atomic_t s_mb_discarded;
atomic_t s_lock_busy;
atomic_t s_extent_cache_cnt;
/* locality groups */
struct ext4_locality_group __percpu *s_locality_groups;
@ -1310,6 +1309,7 @@ struct ext4_sb_info {
/* Reclaim extents from extent status tree */
struct shrinker s_es_shrinker;
struct list_head s_es_lru;
struct percpu_counter s_extent_cache_cnt;
spinlock_t s_es_lru_lock ____cacheline_aligned_in_smp;
};

8
fs/ext4/extents_status.c

@ -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;
}

5
fs/ext4/super.c

@ -783,6 +783,7 @@ static void ext4_put_super(struct super_block *sb)
percpu_counter_destroy(&sbi->s_freeinodes_counter);
percpu_counter_destroy(&sbi->s_dirs_counter);
percpu_counter_destroy(&sbi->s_dirtyclusters_counter);
percpu_counter_destroy(&sbi->s_extent_cache_cnt);
brelse(sbi->s_sbh);
#ifdef CONFIG_QUOTA
for (i = 0; i < MAXQUOTAS; i++)
@ -3688,6 +3689,9 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
if (!err) {
err = percpu_counter_init(&sbi->s_dirtyclusters_counter, 0);
}
if (!err) {
err = percpu_counter_init(&sbi->s_extent_cache_cnt, 0);
}
if (err) {
ext4_msg(sb, KERN_ERR, "insufficient memory");
goto failed_mount3;
@ -3993,6 +3997,7 @@ failed_mount3:
percpu_counter_destroy(&sbi->s_freeinodes_counter);
percpu_counter_destroy(&sbi->s_dirs_counter);
percpu_counter_destroy(&sbi->s_dirtyclusters_counter);
percpu_counter_destroy(&sbi->s_extent_cache_cnt);
if (sbi->s_mmp_tsk)
kthread_stop(sbi->s_mmp_tsk);
failed_mount2:

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