Message-Id: <1397647830-24444-3-git-send-email-wenqing.lz@taobao.com>
Date:	Wed, 16 Apr 2014 19:30:28 +0800
From:	Zheng Liu <gnehzuil.liu@...il.com>
To:	linux-ext4@...r.kernel.org
Cc:	"Theodore Ts'o" <tytso@....edu>,
	Andreas Dilger <adilger.kernel@...ger.ca>,
	Jan Kara <jack@...e.cz>, Zheng Liu <wenqing.lz@...bao.com>
Subject: [RFC PATCH v2 2/4] ext4: track extent status tree shrinker delay statictics

From: Zheng Liu <wenqing.lz@...bao.com>

This commit adds some statictics in extent status tree shrinker.  The
purpose to add these is that we want to collect more details when we
encounter a stall caused by extent status tree shrinker.  Here we count
the following statictics:
  stats:
    the number of all objects on all extent status trees
    the number of reclaimable objects on lru list
    the last sorted interval
    the number of inodes on lru list
  average:
    scan time for shrinking some objects
    the number of shrunk objects
  maximum:
    the inode that has max nr. of objects on lru list
    the maximum scan time for shrinking some objects

The output looks like below:
  $ cat /proc/fs/ext4/sda1/es_shrinker_info
  stats:
    28228 objects
    6341 reclaimable objects
    586 ms last sorted interval
    250 inodes on lru list
  average:
    153 us scan time
    128 shrunk objects
  maximum:
    255 inode (255 objects, 198 reclaimable)
    125723 us max scan time

If the lru list has never been sorted, the following line will not be
printed:
    586ms last sorted interval
If there is an empty lru list, the following lines also will not be
printed:
    250 inodes on lru list
  ...
  maximum:
    255 inode (255 objects, 198 reclaimable)
    0 us max scan time

Meanwhile in this commit a new trace point is defined to print some
details in __ext4_es_shrink().

Cc: "Theodore Ts'o" <tytso@....edu>
Cc: Andreas Dilger <adilger.kernel@...ger.ca>
Cc: Jan Kara <jack@...e.cz>
Reviewed-by: Jan Kara <jack@...e.cz>
Signed-off-by: Zheng Liu <wenqing.lz@...bao.com>
---
 fs/ext4/ext4.h              |    4 +-
 fs/ext4/extents_status.c    |  176 ++++++++++++++++++++++++++++++++++++++++---
 fs/ext4/extents_status.h    |   11 ++-
 fs/ext4/super.c             |   17 ++---
 include/trace/events/ext4.h |   31 ++++++++
 5 files changed, 216 insertions(+), 23 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index f1c65dc..89f3dfa 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -890,6 +890,7 @@ struct ext4_inode_info {
 	struct ext4_es_tree i_es_tree;
 	rwlock_t i_es_lock;
 	struct list_head i_es_lru;
+	unsigned int i_es_all_nr;	/* protected by i_es_lock */
 	unsigned int i_es_lru_nr;	/* protected by i_es_lock */
 	unsigned long i_touch_when;	/* jiffies of last accessing */
 
@@ -1329,8 +1330,7 @@ struct ext4_sb_info {
 	/* Reclaim extents from extent status tree */
 	struct shrinker s_es_shrinker;
 	struct list_head s_es_lru;
-	unsigned long s_es_last_sorted;
-	struct percpu_counter s_extent_cache_cnt;
+	struct ext4_es_stats s_es_stats;
 	struct mb_cache *s_mb_cache;
 	spinlock_t s_es_lru_lock ____cacheline_aligned_in_smp;
 
diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
index 090e69a..9d977a3 100644
--- a/fs/ext4/extents_status.c
+++ b/fs/ext4/extents_status.c
@@ -11,6 +11,8 @@
  */
 #include <linux/rbtree.h>
 #include <linux/list_sort.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
 #include "ext4.h"
 #include "extents_status.h"
 
@@ -313,19 +315,27 @@ 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++;
-		percpu_counter_inc(&EXT4_SB(inode->i_sb)->s_extent_cache_cnt);
+		percpu_counter_inc(&EXT4_SB(inode->i_sb)->
+					s_es_stats.es_stats_lru_cnt);
 	}
 
+	EXT4_I(inode)->i_es_all_nr++;
+	percpu_counter_inc(&EXT4_SB(inode->i_sb)->s_es_stats.es_stats_all_cnt);
+
 	return es;
 }
 
 static void ext4_es_free_extent(struct inode *inode, struct extent_status *es)
 {
+	EXT4_I(inode)->i_es_all_nr--;
+	percpu_counter_dec(&EXT4_SB(inode->i_sb)->s_es_stats.es_stats_all_cnt);
+
 	/* Decrease the lru counter when this es is not delayed */
 	if (!ext4_es_is_delayed(es)) {
 		BUG_ON(EXT4_I(inode)->i_es_lru_nr == 0);
 		EXT4_I(inode)->i_es_lru_nr--;
-		percpu_counter_dec(&EXT4_SB(inode->i_sb)->s_extent_cache_cnt);
+		percpu_counter_dec(&EXT4_SB(inode->i_sb)->
+					s_es_stats.es_stats_lru_cnt);
 	}
 
 	kmem_cache_free(ext4_es_cachep, es);
@@ -927,11 +937,16 @@ static int __ext4_es_shrink(struct ext4_sb_info *sbi, int nr_to_scan,
 			    struct ext4_inode_info *locked_ei)
 {
 	struct ext4_inode_info *ei;
+	struct ext4_es_stats *es_stats;
 	struct list_head *cur, *tmp;
 	LIST_HEAD(skipped);
+	ktime_t start_time;
+	u64 scan_time;
 	int nr_shrunk = 0;
 	int retried = 0, skip_precached = 1, nr_skipped = 0;
 
+	es_stats = &sbi->s_es_stats;
+	start_time = ktime_get();
 	spin_lock(&sbi->s_es_lru_lock);
 
 retry:
@@ -942,7 +957,8 @@ retry:
 		 * If we have already reclaimed all extents from extent
 		 * status tree, just stop the loop immediately.
 		 */
-		if (percpu_counter_read_positive(&sbi->s_extent_cache_cnt) == 0)
+		if (percpu_counter_read_positive(
+				&es_stats->es_stats_lru_cnt) == 0)
 			break;
 
 		ei = list_entry(cur, struct ext4_inode_info, i_es_lru);
@@ -952,7 +968,7 @@ retry:
 		 * time.  Normally we try hard to avoid shrinking
 		 * precached inodes, but we will as a last resort.
 		 */
-		if ((sbi->s_es_last_sorted < ei->i_touch_when) ||
+		if ((es_stats->es_stats_last_sorted < ei->i_touch_when) ||
 		    (skip_precached && ext4_test_inode_state(&ei->vfs_inode,
 						EXT4_STATE_EXT_PRECACHED))) {
 			nr_skipped++;
@@ -986,7 +1002,7 @@ retry:
 	if ((nr_shrunk == 0) && nr_skipped && !retried) {
 		retried++;
 		list_sort(NULL, &sbi->s_es_lru, ext4_inode_touch_time_cmp);
-		sbi->s_es_last_sorted = jiffies;
+		es_stats->es_stats_last_sorted = jiffies;
 		ei = list_first_entry(&sbi->s_es_lru, struct ext4_inode_info,
 				      i_es_lru);
 		/*
@@ -1004,6 +1020,22 @@ retry:
 	if (locked_ei && nr_shrunk == 0)
 		nr_shrunk = __es_try_to_reclaim_extents(locked_ei, nr_to_scan);
 
+	scan_time = ktime_to_ns(ktime_sub(ktime_get(), start_time));
+	if (likely(es_stats->es_stats_scan_time))
+		es_stats->es_stats_scan_time = (scan_time +
+				es_stats->es_stats_scan_time*3) / 4;
+	else
+		es_stats->es_stats_scan_time = scan_time;
+	if (scan_time > es_stats->es_stats_max_scan_time)
+		es_stats->es_stats_max_scan_time = scan_time;
+	if (likely(es_stats->es_stats_shrunk))
+		es_stats->es_stats_shrunk = (nr_shrunk +
+				es_stats->es_stats_shrunk*3) / 4;
+	else
+		es_stats->es_stats_shrunk = nr_shrunk;
+
+	trace_ext4_es_shrink(sbi->s_sb, nr_shrunk, scan_time, skip_precached,
+			     nr_skipped, retried);
 	return nr_shrunk;
 }
 
@@ -1014,7 +1046,7 @@ static unsigned long ext4_es_count(struct shrinker *shrink,
 	struct ext4_sb_info *sbi;
 
 	sbi = container_of(shrink, struct ext4_sb_info, s_es_shrinker);
-	nr = percpu_counter_read_positive(&sbi->s_extent_cache_cnt);
+	nr = percpu_counter_read_positive(&sbi->s_es_stats.es_stats_lru_cnt);
 	trace_ext4_es_shrink_count(sbi->s_sb, sc->nr_to_scan, nr);
 	return nr;
 }
@@ -1027,7 +1059,7 @@ static unsigned long ext4_es_scan(struct shrinker *shrink,
 	int nr_to_scan = sc->nr_to_scan;
 	int ret, nr_shrunk;
 
-	ret = percpu_counter_read_positive(&sbi->s_extent_cache_cnt);
+	ret = percpu_counter_read_positive(&sbi->s_es_stats.es_stats_lru_cnt);
 	trace_ext4_es_shrink_scan_enter(sbi->s_sb, nr_to_scan, ret);
 
 	if (!nr_to_scan)
@@ -1039,19 +1071,143 @@ static unsigned long ext4_es_scan(struct shrinker *shrink,
 	return nr_shrunk;
 }
 
-void ext4_es_register_shrinker(struct ext4_sb_info *sbi)
+static void *ext4_es_seq_shrinker_info_start(struct seq_file *seq, loff_t *pos)
+{
+	return *pos ? NULL : SEQ_START_TOKEN;
+}
+
+static void *
+ext4_es_seq_shrinker_info_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+	return NULL;
+}
+
+static int ext4_es_seq_shrinker_info_show(struct seq_file *seq, void *v)
+{
+	struct ext4_sb_info *sbi = seq->private;
+	struct ext4_es_stats *es_stats = &sbi->s_es_stats;
+	struct ext4_inode_info *ei, *max = NULL;
+	unsigned int inode_cnt = 0;
+
+	if (v != SEQ_START_TOKEN)
+		return 0;
+
+	/* here we just find an inode that has the max nr. of objects */
+	spin_lock(&sbi->s_es_lru_lock);
+	list_for_each_entry(ei, &sbi->s_es_lru, i_es_lru) {
+		inode_cnt++;
+		if (max && max->i_es_all_nr < ei->i_es_all_nr)
+			max = ei;
+		else if (!max)
+			max = ei;
+	}
+	spin_unlock(&sbi->s_es_lru_lock);
+
+	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_lru_cnt));
+	if (es_stats->es_stats_last_sorted != 0)
+		seq_printf(seq, "  %u ms last sorted interval\n",
+			   jiffies_to_msecs(jiffies -
+					    es_stats->es_stats_last_sorted));
+	if (inode_cnt)
+		seq_printf(seq, "  %d inodes on lru list\n", inode_cnt);
+
+	seq_printf(seq, "average:\n  %llu us scan time\n",
+	    div_u64(es_stats->es_stats_scan_time, 1000));
+	seq_printf(seq, "  %lu shrunk objects\n", es_stats->es_stats_shrunk);
+	if (inode_cnt)
+		seq_printf(seq,
+		    "maximum:\n  %lu inode (%u objects, %u reclaimable)\n"
+		    "  %llu us max scan time\n",
+		    max->vfs_inode.i_ino, max->i_es_all_nr, max->i_es_lru_nr,
+		    div_u64(es_stats->es_stats_max_scan_time, 1000));
+
+	return 0;
+}
+
+static void ext4_es_seq_shrinker_info_stop(struct seq_file *seq, void *v)
 {
+}
+
+static const struct seq_operations ext4_es_seq_shrinker_info_ops = {
+	.start = ext4_es_seq_shrinker_info_start,
+	.next  = ext4_es_seq_shrinker_info_next,
+	.stop  = ext4_es_seq_shrinker_info_stop,
+	.show  = ext4_es_seq_shrinker_info_show,
+};
+
+static int
+ext4_es_seq_shrinker_info_open(struct inode *inode, struct file *file)
+{
+	int ret;
+
+	ret = seq_open(file, &ext4_es_seq_shrinker_info_ops);
+	if (!ret) {
+		struct seq_file *m = file->private_data;
+		m->private = PDE_DATA(inode);
+	}
+
+	return ret;
+}
+
+static int
+ext4_es_seq_shrinker_info_release(struct inode *inode, struct file *file)
+{
+	return seq_release(inode, file);
+}
+
+static const struct file_operations ext4_es_seq_shrinker_info_fops = {
+	.owner		= THIS_MODULE,
+	.open		= ext4_es_seq_shrinker_info_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= ext4_es_seq_shrinker_info_release,
+};
+
+int ext4_es_register_shrinker(struct ext4_sb_info *sbi)
+{
+	int err;
+
 	INIT_LIST_HEAD(&sbi->s_es_lru);
 	spin_lock_init(&sbi->s_es_lru_lock);
-	sbi->s_es_last_sorted = 0;
+	sbi->s_es_stats.es_stats_last_sorted = 0;
+	sbi->s_es_stats.es_stats_shrunk = 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);
+	if (err)
+		return err;
+	err = percpu_counter_init(&sbi->s_es_stats.es_stats_lru_cnt, 0);
+	if (err)
+		goto err1;
+
 	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;
-	register_shrinker(&sbi->s_es_shrinker);
+	err = register_shrinker(&sbi->s_es_shrinker);
+	if (err)
+		goto err2;
+
+	if (sbi->s_proc)
+		proc_create_data("es_shrinker_info", S_IRUGO, sbi->s_proc,
+				 &ext4_es_seq_shrinker_info_fops, sbi);
+
+	return 0;
+
+err2:
+	percpu_counter_destroy(&sbi->s_es_stats.es_stats_lru_cnt);
+err1:
+	percpu_counter_destroy(&sbi->s_es_stats.es_stats_all_cnt);
+	return err;
 }
 
 void ext4_es_unregister_shrinker(struct ext4_sb_info *sbi)
 {
+	if (sbi->s_proc)
+		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_lru_cnt);
 	unregister_shrinker(&sbi->s_es_shrinker);
 }
 
diff --git a/fs/ext4/extents_status.h b/fs/ext4/extents_status.h
index f1b62a4..647c3c9 100644
--- a/fs/ext4/extents_status.h
+++ b/fs/ext4/extents_status.h
@@ -64,6 +64,15 @@ struct ext4_es_tree {
 	struct extent_status *cache_es;	/* recently accessed extent */
 };
 
+struct ext4_es_stats {
+	unsigned long es_stats_last_sorted;
+	unsigned long es_stats_shrunk;
+	u64 es_stats_scan_time;
+	u64 es_stats_max_scan_time;
+	struct percpu_counter es_stats_all_cnt;
+	struct percpu_counter es_stats_lru_cnt;
+};
+
 extern int __init ext4_init_es(void);
 extern void ext4_exit_es(void);
 extern void ext4_es_init_tree(struct ext4_es_tree *tree);
@@ -138,7 +147,7 @@ static inline void ext4_es_store_pblock_status(struct extent_status *es,
 		       (pb & ~ES_MASK));
 }
 
-extern void ext4_es_register_shrinker(struct ext4_sb_info *sbi);
+extern int ext4_es_register_shrinker(struct ext4_sb_info *sbi);
 extern void ext4_es_unregister_shrinker(struct ext4_sb_info *sbi);
 extern void ext4_es_lru_add(struct inode *inode);
 extern void ext4_es_lru_del(struct inode *inode);
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index f3c6670..df0fb22 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -820,7 +820,6 @@ 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++)
@@ -884,6 +883,7 @@ static struct inode *ext4_alloc_inode(struct super_block *sb)
 	ext4_es_init_tree(&ei->i_es_tree);
 	rwlock_init(&ei->i_es_lock);
 	INIT_LIST_HEAD(&ei->i_es_lru);
+	ei->i_es_all_nr = 0;
 	ei->i_es_lru_nr = 0;
 	ei->i_touch_when = 0;
 	ei->i_reserved_data_blocks = 0;
@@ -3890,10 +3890,11 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	sbi->s_err_report.data = (unsigned long) sb;
 
 	/* Register extent status tree shrinker */
-	ext4_es_register_shrinker(sbi);
-
-	err = percpu_counter_init(&sbi->s_freeclusters_counter,
-			ext4_count_free_clusters(sb));
+	err = ext4_es_register_shrinker(sbi);
+	if (!err) {
+		err = percpu_counter_init(&sbi->s_freeclusters_counter,
+				ext4_count_free_clusters(sb));
+	}
 	if (!err) {
 		err = percpu_counter_init(&sbi->s_freeinodes_counter,
 				ext4_count_free_inodes(sb));
@@ -3905,9 +3906,6 @@ 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;
@@ -4220,8 +4218,8 @@ failed_mount_wq:
 		jbd2_journal_destroy(sbi->s_journal);
 		sbi->s_journal = NULL;
 	}
-failed_mount3:
 	ext4_es_unregister_shrinker(sbi);
+failed_mount3:
 	del_timer_sync(&sbi->s_err_report);
 	if (sbi->s_flex_groups)
 		ext4_kvfree(sbi->s_flex_groups);
@@ -4229,7 +4227,6 @@ 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:
diff --git a/include/trace/events/ext4.h b/include/trace/events/ext4.h
index c1d7a7c..996e58b 100644
--- a/include/trace/events/ext4.h
+++ b/include/trace/events/ext4.h
@@ -2460,6 +2460,37 @@ TRACE_EVENT(ext4_collapse_range,
 		  __entry->offset, __entry->len)
 );
 
+TRACE_EVENT(ext4_es_shrink,
+	TP_PROTO(struct super_block *sb, int nr_shrunk, u64 scan_time,
+		 int skip_precached, int nr_skipped, int retried),
+
+	TP_ARGS(sb, nr_shrunk, scan_time, skip_precached, nr_skipped, retried),
+
+	TP_STRUCT__entry(
+		__field(	dev_t,		dev		)
+		__field(	int,		nr_shrunk	)
+		__field(	unsigned long long, scan_time	)
+		__field(	int,		skip_precached	)
+		__field(	int,		nr_skipped	)
+		__field(	int,		retried		)
+	),
+
+	TP_fast_assign(
+		__entry->dev		= sb->s_dev;
+		__entry->nr_shrunk	= nr_shrunk;
+		__entry->scan_time	= div_u64(scan_time, 1000);
+		__entry->skip_precached = skip_precached;
+		__entry->nr_skipped	= nr_skipped;
+		__entry->retried	= retried;
+	),
+
+	TP_printk("dev %d,%d nr_shrunk %d, scan_time %llu skip_precached %d "
+		  "nr_skipped %d retried %d",
+		  MAJOR(__entry->dev), MINOR(__entry->dev), __entry->nr_shrunk,
+		  __entry->scan_time, __entry->skip_precached,
+		  __entry->nr_skipped, __entry->retried)
+);
+
 #endif /* _TRACE_EXT4_H */
 
 /* This part must be outside protection */
-- 
1.7.9.7

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