[PATCH] ext4: change the type of ext4 cache stats to percpu_counter to improve performance

[Shaokun Zhang]

From: Yang Guo <guoya...@huawei.com>

@es_stats_cache_hits and @es_stats_cache_misses are accessed frequently in
ext4_es_lookup_extent function, it would influence the ext4 read/write
performance in NUMA system.
Let's optimize it using percpu_counter, it is profitable for the
performance.

The test command is as below:
fio -name=randwrite -numjobs=8 -filename=/mnt/test1 -rw=randwrite
-ioengine=libaio -direct=1 -iodepth=64 -sync=0 -norandommap -group_reporting
-runtime=120 -time_based -bs=4k -size=5G

And the result is better 10% than the initial implement:
without the patch，IOPS=197k, BW=770MiB/s (808MB/s)(90.3GiB/120002msec)
with the patch,  IOPS=218k, BW=852MiB/s (894MB/s)(99.9GiB/120002msec)

Cc: "Theodore Ts'o" <ty...@mit.edu>
Cc: Andreas Dilger <adilger.ker...@dilger.ca>
Signed-off-by: Yang Guo <guoya...@huawei.com>
Signed-off-by: Shaokun Zhang <zhangshao...@hisilicon.com>
---
 fs/ext4/extents_status.c | 20 +++++++++++++-------
 fs/ext4/extents_status.h |  4 ++--
 2 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
index 7521de2dcf3a..7699e80ae236 100644
--- a/fs/ext4/extents_status.c
+++ b/fs/ext4/extents_status.c
@@ -947,9 +947,9 @@ int ext4_es_lookup_extent(struct inode *inode, ext4_lblk_t 
lblk,
                es->es_pblk = es1->es_pblk;
                if (!ext4_es_is_referenced(es1))
                        ext4_es_set_referenced(es1);
-               stats->es_stats_cache_hits++;
+               percpu_counter_inc(&stats->es_stats_cache_hits);
        } else {
-               stats->es_stats_cache_misses++;
+               percpu_counter_inc(&stats->es_stats_cache_misses);
        }
 
        read_unlock(&EXT4_I(inode)->i_es_lock);
@@ -1235,9 +1235,9 @@ int ext4_seq_es_shrinker_info_show(struct seq_file *seq, 
void *v)
        seq_printf(seq, "stats:\n  %lld objects\n  %lld reclaimable objects\n",
                   percpu_counter_sum_positive(&es_stats->es_stats_all_cnt),
                   percpu_counter_sum_positive(&es_stats->es_stats_shk_cnt));
-       seq_printf(seq, "  %lu/%lu cache hits/misses\n",
-                  es_stats->es_stats_cache_hits,
-                  es_stats->es_stats_cache_misses);
+       seq_printf(seq, "  %llu/%llu cache hits/misses\n",
+                  percpu_counter_sum_positive(&es_stats->es_stats_cache_hits),
+                  
percpu_counter_sum_positive(&es_stats->es_stats_cache_misses));
        if (inode_cnt)
                seq_printf(seq, "  %d inodes on list\n", inode_cnt);
 
@@ -1264,8 +1264,14 @@ int ext4_es_register_shrinker(struct ext4_sb_info *sbi)
        sbi->s_es_nr_inode = 0;
        spin_lock_init(&sbi->s_es_lock);
        sbi->s_es_stats.es_stats_shrunk = 0;
-       sbi->s_es_stats.es_stats_cache_hits = 0;
-       sbi->s_es_stats.es_stats_cache_misses = 0;
+       err = percpu_counter_init(&sbi->s_es_stats.es_stats_cache_hits, 0,
+                                 GFP_KERNEL);
+       if (err)
+               return err;
+       err = percpu_counter_init(&sbi->s_es_stats.es_stats_cache_misses, 0,
+                                 GFP_KERNEL);
+       if (err)
+               return err;
        sbi->s_es_stats.es_stats_scan_time = 0;
        sbi->s_es_stats.es_stats_max_scan_time = 0;
        err = percpu_counter_init(&sbi->s_es_stats.es_stats_all_cnt, 0, 
GFP_KERNEL);
diff --git a/fs/ext4/extents_status.h b/fs/ext4/extents_status.h
index 131a8b7df265..e722dd9bd06e 100644
--- a/fs/ext4/extents_status.h
+++ b/fs/ext4/extents_status.h
@@ -70,8 +70,8 @@ struct ext4_es_tree {
 
 struct ext4_es_stats {
        unsigned long es_stats_shrunk;
-       unsigned long es_stats_cache_hits;
-       unsigned long es_stats_cache_misses;
+       struct percpu_counter es_stats_cache_hits;
+       struct percpu_counter es_stats_cache_misses;
        u64 es_stats_scan_time;
        u64 es_stats_max_scan_time;
        struct percpu_counter es_stats_all_cnt;
-- 
2.7.4