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Date: Tue, 14 Jan 2014 14:24:00 +0100
From: Jan Kara <jack@...e.cz>
To: Zheng Liu <gnehzuil.liu@...il.com>
Cc: linux-ext4@...r.kernel.org, Theodore Ts'o <tytso@....edu>,
Andreas Dilger <adilger.kernel@...ger.ca>,
Jan Kara <jack@...e.cz>, Zheng Liu <wenqing.lz@...bao.com>
Subject: Re: [RFC PATCH 2/2] ext4: track extent status tree shrinker delay
statictics
On Tue 14-01-14 16:06:41, Zheng Liu wrote:
> 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 output looks like below:
> $ cat /proc/fs/ext4/sda1/es_shrinker_info
> stats:
> 28228 objects
> 6341 reclaimable objects
> 586ms last sorted interval
> 250 inodes on lru list
> average:
> 153us scan time
> 128 shrunk objects
> maximum:
> 255 inode (255 objects, 198 reclaimable)
>
> 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)
>
> Meanwhile in this commit a new trace point is defined to print some
> details in __ext4_es_shrink().
The patch looks good. You can add:
Reviewed-by: Jan Kara <jack@...e.cz>
Honza
>
> Cc: "Theodore Ts'o" <tytso@....edu>
> Cc: Andreas Dilger <adilger.kernel@...ger.ca>
> Cc: Jan Kara <jack@...e.cz>
> Signed-off-by: Zheng Liu <wenqing.lz@...bao.com>
> ---
> fs/ext4/ext4.h | 4 +-
> fs/ext4/extents_status.c | 171 ++++++++++++++++++++++++++++++++++++++++---
> fs/ext4/extents_status.h | 10 ++-
> fs/ext4/super.c | 17 ++---
> include/trace/events/ext4.h | 31 ++++++++
> 5 files changed, 210 insertions(+), 23 deletions(-)
>
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index ece5556..23ce6b7 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -885,6 +885,7 @@ 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 */
>
> @@ -1322,8 +1323,7 @@ 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;
> spinlock_t s_es_lru_lock ____cacheline_aligned_in_smp;
>
> /* Ratelimit ext4 messages. */
> diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
> index eb7ae61..5cb25c5 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);
> @@ -929,11 +939,16 @@ 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:
> @@ -944,7 +959,8 @@ 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);
> @@ -954,7 +970,7 @@ 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++;
> @@ -988,7 +1004,7 @@ 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);
> /*
> @@ -1006,6 +1022,20 @@ 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 (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;
> }
>
> @@ -1016,7 +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;
> }
> @@ -1029,7 +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)
> @@ -1041,19 +1071,140 @@ 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, " %ums 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 %lluus 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",
> + max->vfs_inode.i_ino, max->i_es_all_nr, max->i_es_lru_nr);
> +
> + 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;
> + 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 167f4ab8..37a4313 100644
> --- a/fs/ext4/extents_status.h
> +++ b/fs/ext4/extents_status.h
> @@ -64,6 +64,14 @@ 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;
> + 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);
> @@ -129,7 +137,7 @@ static inline void ext4_es_store_status(struct extent_status *es,
> (es->es_pblk & ~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 1f7784d..9c3a8bd 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -819,7 +819,6 @@ 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++)
> @@ -879,6 +878,7 @@ 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;
> @@ -3869,10 +3869,11 @@ 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));
> @@ -3884,9 +3885,6 @@ 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;
> @@ -4191,8 +4189,8 @@ 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);
> @@ -4200,7 +4198,6 @@ 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 35d28f8..a05a16d 100644
> --- a/include/trace/events/ext4.h
> +++ b/include/trace/events/ext4.h
> @@ -2422,6 +2422,37 @@ TRACE_EVENT(ext4_es_shrink_scan_exit,
> __entry->nr_shrunk, __entry->cache_cnt)
> );
>
> +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
>
--
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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