From: Waiman Long Subject: [PATCH v2 4/4] ext4: Make cache hits/misses per-cpu counts Date: Fri, 8 Apr 2016 12:16:22 -0400 Message-ID: <1460132182-11690-5-git-send-email-Waiman.Long@hpe.com> References: <1460132182-11690-1-git-send-email-Waiman.Long@hpe.com> Cc: linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, Scott J Norton , Douglas Hatch , Toshimitsu Kani , Waiman Long To: "Theodore Ts'o" , Andreas Dilger , Tejun Heo , Christoph Lameter Return-path: In-Reply-To: <1460132182-11690-1-git-send-email-Waiman.Long@hpe.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org This patch changes the es_stats_cache_hits and es_stats_cache_misses statistics counts to per-cpu variables to reduce cacheline contention issues whem multiple threads are trying to update those counts simultaneously. It uses the new per-cpu stats APIs provided by the percpu_stats.h header file. 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 10173MB/s 16141MB/s +58.7% Read-write 2830MB/s 4315MB/s +52.5% Signed-off-by: Waiman Long --- fs/ext4/extents_status.c | 22 +++++++++++++--------- fs/ext4/extents_status.h | 11 +++++++++-- 2 files changed, 22 insertions(+), 11 deletions(-) diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c index e38b987..bfa8d63 100644 --- a/fs/ext4/extents_status.c +++ b/fs/ext4/extents_status.c @@ -825,9 +825,9 @@ out: es->es_pblk = es1->es_pblk; if (!ext4_es_is_referenced(es1)) ext4_es_set_referenced(es1); - stats->es_stats_cache_hits++; + percpu_stats_inc(&stats->es_stats, es_stats_cache_hits); } else { - stats->es_stats_cache_misses++; + percpu_stats_inc(&stats->es_stats, es_stats_cache_misses); } read_unlock(&EXT4_I(inode)->i_es_lock); @@ -1113,9 +1113,9 @@ 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_stats_sum(&es_stats->es_stats, es_stats_cache_hits), + percpu_stats_sum(&es_stats->es_stats, es_stats_cache_misses)); if (inode_cnt) seq_printf(seq, " %d inodes on list\n", inode_cnt); @@ -1142,8 +1142,6 @@ 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); @@ -1153,15 +1151,20 @@ int ext4_es_register_shrinker(struct ext4_sb_info *sbi) if (err) goto err1; + err = percpu_stats_init(&sbi->s_es_stats.es_stats, es_stats_cnt, 0); + if (err) + goto err2; + 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 err3; return 0; - +err3: + percpu_stats_destroy(&sbi->s_es_stats.es_stats); err2: percpu_counter_destroy(&sbi->s_es_stats.es_stats_shk_cnt); err1: @@ -1173,6 +1176,7 @@ void ext4_es_unregister_shrinker(struct ext4_sb_info *sbi) { percpu_counter_destroy(&sbi->s_es_stats.es_stats_all_cnt); percpu_counter_destroy(&sbi->s_es_stats.es_stats_shk_cnt); + percpu_stats_destroy(&sbi->s_es_stats.es_stats); unregister_shrinker(&sbi->s_es_shrinker); } diff --git a/fs/ext4/extents_status.h b/fs/ext4/extents_status.h index f7aa24f..c163189 100644 --- a/fs/ext4/extents_status.h +++ b/fs/ext4/extents_status.h @@ -11,6 +11,8 @@ #ifndef _EXT4_EXTENTS_STATUS_H #define _EXT4_EXTENTS_STATUS_H +#include + /* * Turn on ES_DEBUG__ to get lots of info about extent status operations. */ @@ -67,10 +69,15 @@ struct ext4_es_tree { struct extent_status *cache_es; /* recently accessed extent */ }; +enum ext4_es_stat_type { + es_stats_cache_hits, + es_stats_cache_misses, + es_stats_cnt, +}; + struct ext4_es_stats { unsigned long es_stats_shrunk; - unsigned long es_stats_cache_hits; - unsigned long es_stats_cache_misses; + struct percpu_stats es_stats; u64 es_stats_scan_time; u64 es_stats_max_scan_time; struct percpu_counter es_stats_all_cnt; -- 1.7.1