use-percpu_counter-for-extent_cache-hits-misses

   1 ext4: use percpu_counters for extent_status cache hits/misses
   2
   3 From: Yang Guo <guoyang2@huawei.com>
   4
   5 @es_stats_cache_hits and @es_stats_cache_misses are accessed frequently in
   6 ext4_es_lookup_extent function, it would influence the ext4 read/write
   7 performance in NUMA system.
   8 Let's optimize it using percpu_counter, it is profitable for the
   9 performance.
  10
  11 The test command is as below:
  12 fio -name=randwrite -numjobs=8 -filename=/mnt/test1 -rw=randwrite
  13 -ioengine=libaio -direct=1 -iodepth=64 -sync=0 -norandommap -group_reporting
  14 -runtime=120 -time_based -bs=4k -size=5G
  15
  16 And the result is better 10% than the initial implement:
  17 without the patch，IOPS=197k, BW=770MiB/s (808MB/s)(90.3GiB/120002msec)
  18 with the patch,  IOPS=218k, BW=852MiB/s (894MB/s)(99.9GiB/120002msec)
  19
  20 Cc: Andreas Dilger <adilger.kernel@dilger.ca>
  21 Signed-off-by: Yang Guo <guoyang2@huawei.com>
  22 Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com>
  23 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
  24 ---
  25  fs/ext4/extents_status.c | 20 +++++++++++++-------
  26  fs/ext4/extents_status.h |  4 ++--
  27  2 files changed, 15 insertions(+), 9 deletions(-)
  28
  29 diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
  30 index e977c560992c..dc28a9642452 100644
  31 --- a/fs/ext4/extents_status.c
  32 +++ b/fs/ext4/extents_status.c
  33 @@ -948,7 +948,7 @@ int ext4_es_lookup_extent(struct inode *inode, ext4_lblk_t lblk,
  34                 es->es_pblk = es1->es_pblk;
  35                 if (!ext4_es_is_referenced(es1))
  36                         ext4_es_set_referenced(es1);
  37 -               stats->es_stats_cache_hits++;
  38 +               percpu_counter_inc(&stats->es_stats_cache_hits);
  39                 if (next_lblk) {
  40                         node = rb_next(&es1->rb_node);
  41                         if (node) {
  42 @@ -959,7 +959,7 @@ int ext4_es_lookup_extent(struct inode *inode, ext4_lblk_t lblk,
  43                                 *next_lblk = 0;
  44                 }
  45         } else {
  46 -               stats->es_stats_cache_misses++;
  47 +               percpu_counter_inc(&stats->es_stats_cache_misses);
  48         }
  49
  50         read_unlock(&EXT4_I(inode)->i_es_lock);
  51 @@ -1586,9 +1586,9 @@ int ext4_seq_es_shrinker_info_show(struct seq_file *seq, void *v)
  52         seq_printf(seq, "stats:\n  %lld objects\n  %lld reclaimable objects\n",
  53                    percpu_counter_sum_positive(&es_stats->es_stats_all_cnt),
  54                    percpu_counter_sum_positive(&es_stats->es_stats_shk_cnt));
  55 -       seq_printf(seq, "  %lu/%lu cache hits/misses\n",
  56 -                  es_stats->es_stats_cache_hits,
  57 -                  es_stats->es_stats_cache_misses);
  58 +       seq_printf(seq, "  %llu/%llu cache hits/misses\n",
  59 +                  percpu_counter_sum_positive(&es_stats->es_stats_cache_hits),
  60 +                  percpu_counter_sum_positive(&es_stats->es_stats_cache_misses));
  61         if (inode_cnt)
  62                 seq_printf(seq, "  %d inodes on list\n", inode_cnt);
  63
  64 @@ -1615,8 +1615,14 @@ int ext4_es_register_shrinker(struct ext4_sb_info *sbi)
  65         sbi->s_es_nr_inode = 0;
  66         spin_lock_init(&sbi->s_es_lock);
  67         sbi->s_es_stats.es_stats_shrunk = 0;
  68 -       sbi->s_es_stats.es_stats_cache_hits = 0;
  69 -       sbi->s_es_stats.es_stats_cache_misses = 0;
  70 +       err = percpu_counter_init(&sbi->s_es_stats.es_stats_cache_hits, 0,
  71 +                                 GFP_KERNEL);
  72 +       if (err)
  73 +               return err;
  74 +       err = percpu_counter_init(&sbi->s_es_stats.es_stats_cache_misses, 0,
  75 +                                 GFP_KERNEL);
  76 +       if (err)
  77 +               return err;
  78         sbi->s_es_stats.es_stats_scan_time = 0;
  79         sbi->s_es_stats.es_stats_max_scan_time = 0;
  80         err = percpu_counter_init(&sbi->s_es_stats.es_stats_all_cnt, 0, GFP_KERNEL);
  81 diff --git a/fs/ext4/extents_status.h b/fs/ext4/extents_status.h
  82 index 5e5c4a40d863..825313c59752 100644
  83 --- a/fs/ext4/extents_status.h
  84 +++ b/fs/ext4/extents_status.h
  85 @@ -70,8 +70,8 @@ struct ext4_es_tree {
  86
  87  struct ext4_es_stats {
  88         unsigned long es_stats_shrunk;
  89 -       unsigned long es_stats_cache_hits;
  90 -       unsigned long es_stats_cache_misses;
  91 +       struct percpu_counter es_stats_cache_hits;
  92 +       struct percpu_counter es_stats_cache_misses;
  93         u64 es_stats_scan_time;
  94         u64 es_stats_max_scan_time;
  95         struct percpu_counter es_stats_all_cnt;