From: Waiman Long <waiman.l...@hpe.com> This patch changes the es_stats_cache_hits and es_stats_cache_misses statistics counts to percpu counters to reduce cacheline contention issues whem multiple threads are trying to update those counts simultaneously.
With a 38-threads fio I/O test with 2 shared files (on DAX-mount NVDIMM) running on a 4-socket Haswell-EX server with 4.6-rc1 kernel, the aggregated bandwidths before and after the patch were: Test W/O patch With patch % change ---- --------- ---------- -------- Read-only 16499MB/s 17215MB/s +4.3% Read-write 4361MB/s 4794MB/s +9.9% Signed-off-by: Waiman Long <waiman.l...@hpe.com> The patch is not in mainstream yet, but was ack-ed already: https://lkml.org/lkml/2016/4/29/584 This patch does not improve the performance of __es_shrink() itself, but generally improves the fastpath. Was found while digging: https://jira.sw.ru/browse/PSBM-83335 Signed-off-by: Konstantin Khorenko <khore...@virtuozzo.com> --- fs/ext4/extents_status.c | 38 +++++++++++++++++++++++++++++--------- fs/ext4/extents_status.h | 4 ++-- 2 files changed, 31 insertions(+), 11 deletions(-) diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c index 77f44d382aa5..a3b9c480ec20 100644 --- a/fs/ext4/extents_status.c +++ b/fs/ext4/extents_status.c @@ -769,6 +769,15 @@ void ext4_es_cache_extent(struct inode *inode, ext4_lblk_t lblk, write_unlock(&EXT4_I(inode)->i_es_lock); } +/* + * For pure statistics count, use a large batch size to make sure that + * it does percpu update as much as possible. + */ +static inline void ext4_es_stats_inc(struct percpu_counter *fbc) +{ + __percpu_counter_add(fbc, 1, (1 << 30)); +} + /* * ext4_es_lookup_extent() looks up an extent in extent status tree. * @@ -823,9 +832,9 @@ int ext4_es_lookup_extent(struct inode *inode, ext4_lblk_t lblk, es->es_lblk = es1->es_lblk; es->es_len = es1->es_len; es->es_pblk = es1->es_pblk; - stats->es_stats_cache_hits++; + ext4_es_stats_inc(&stats->es_stats_cache_hits); } else { - stats->es_stats_cache_misses++; + ext4_es_stats_inc(&stats->es_stats_cache_misses); } read_unlock(&EXT4_I(inode)->i_es_lock); @@ -1122,9 +1131,9 @@ static int ext4_es_seq_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, " %lld/%lld 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); @@ -1188,8 +1197,6 @@ 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; 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); @@ -1199,19 +1206,30 @@ int ext4_es_register_shrinker(struct ext4_sb_info *sbi) if (err) goto err1; + err = percpu_counter_init(&sbi->s_es_stats.es_stats_cache_hits, 0, GFP_KERNEL); + if (err) + goto err2; + + err = percpu_counter_init(&sbi->s_es_stats.es_stats_cache_misses, 0, GFP_KERNEL); + if (err) + goto err3; + sbi->s_es_shrinker.scan_objects = ext4_es_scan; sbi->s_es_shrinker.count_objects = ext4_es_count; sbi->s_es_shrinker.seeks = DEFAULT_SEEKS; err = register_shrinker(&sbi->s_es_shrinker); if (err) - goto err2; + goto err4; if (sbi->s_proc) proc_create_data("es_shrinker_info", S_IRUGO, sbi->s_proc, &ext4_es_seq_shrinker_info_fops, sbi); return 0; - +err4: + percpu_counter_destroy(&sbi->s_es_stats.es_stats_cache_misses); +err3: + percpu_counter_destroy(&sbi->s_es_stats.es_stats_cache_hits); err2: percpu_counter_destroy(&sbi->s_es_stats.es_stats_shk_cnt); err1: @@ -1225,6 +1243,8 @@ void ext4_es_unregister_shrinker(struct ext4_sb_info *sbi) remove_proc_entry("es_shrinker_info", sbi->s_proc); percpu_counter_destroy(&sbi->s_es_stats.es_stats_all_cnt); percpu_counter_destroy(&sbi->s_es_stats.es_stats_shk_cnt); + percpu_counter_destroy(&sbi->s_es_stats.es_stats_cache_hits); + percpu_counter_destroy(&sbi->s_es_stats.es_stats_cache_misses); unregister_shrinker(&sbi->s_es_shrinker); } diff --git a/fs/ext4/extents_status.h b/fs/ext4/extents_status.h index b0b78b95f481..ddebb0e255ca 100644 --- a/fs/ext4/extents_status.h +++ b/fs/ext4/extents_status.h @@ -66,10 +66,10 @@ 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; u64 es_stats_scan_time; u64 es_stats_max_scan_time; + struct percpu_counter es_stats_cache_hits; + struct percpu_counter es_stats_cache_misses; struct percpu_counter es_stats_all_cnt; struct percpu_counter es_stats_shk_cnt; }; -- 2.15.1 _______________________________________________ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel
