Commit 1ac6466f authored by Theodore Ts'o's avatar Theodore Ts'o
Browse files

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: default avatarEric Sandeen <sandeen@redhat.com>
Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent 24630774

fs/ext4/ext4.h

+1 −1
Original line number Diff line number Diff line
@@ -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;

};

fs/ext4/extents_status.c

+4 −4
Original line number Diff line number Diff line
@@ -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;

}

fs/ext4/super.c

+5 −0
Original line number Diff line number Diff line
@@ -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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