ext4: track extent status tree shrinker delay statictics
authorZheng Liu <wenqing.lz@taobao.com>
Tue, 2 Sep 2014 02:26:49 +0000 (22:26 -0400)
committerTheodore Ts'o <tytso@mit.edu>
Tue, 2 Sep 2014 02:26:49 +0000 (22:26 -0400)
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
    cache hits/misses
    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
    5281/631 cache hits/misses
    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: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
fs/ext4/ext4.h
fs/ext4/extents_status.c
fs/ext4/extents_status.h
fs/ext4/super.c
include/trace/events/ext4.h

index c07f43f8eb939f610725478406b122b8c84bd634..00fd822ac6e4562ddf267fb56b31d5d8dec2f8e0 100644 (file)
@@ -891,6 +891,7 @@ 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 */
 
@@ -1331,8 +1332,7 @@ 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;
 
index 95da65c60d834a81fbe3ca099eb54258a16c78e8..09fd5766726223fbd8ae30caa67cc80c9041fe8c 100644 (file)
@@ -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);
@@ -729,6 +739,7 @@ int ext4_es_lookup_extent(struct inode *inode, ext4_lblk_t lblk,
                          struct extent_status *es)
 {
        struct ext4_es_tree *tree;
+       struct ext4_es_stats *stats;
        struct extent_status *es1 = NULL;
        struct rb_node *node;
        int found = 0;
@@ -765,11 +776,15 @@ int ext4_es_lookup_extent(struct inode *inode, ext4_lblk_t lblk,
        }
 
 out:
+       stats = &EXT4_SB(inode->i_sb)->s_es_stats;
        if (found) {
                BUG_ON(!es1);
                es->es_lblk = es1->es_lblk;
                es->es_len = es1->es_len;
                es->es_pblk = es1->es_pblk;
+               stats->es_stats_cache_hits++;
+       } else {
+               stats->es_stats_cache_misses++;
        }
 
        read_unlock(&EXT4_I(inode)->i_es_lock);
@@ -931,11 +946,16 @@ 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:
@@ -946,7 +966,8 @@ 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);
@@ -956,7 +977,7 @@ 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++;
@@ -990,7 +1011,7 @@ 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);
                /*
@@ -1008,6 +1029,22 @@ 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;
 }
 
@@ -1018,7 +1055,7 @@ 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;
 }
@@ -1031,7 +1068,7 @@ 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)
@@ -1043,19 +1080,148 @@ 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));
+       seq_printf(seq, "  %lu/%lu cache hits/misses\n",
+                  es_stats->es_stats_cache_hits,
+                  es_stats->es_stats_cache_misses);
+       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_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);
+       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);
 }
 
index f1b62a41992059f3cbebd16ee6caaf25ee156283..efd5f970b5013085dec20e421b8ff3ced53246c2 100644 (file)
@@ -64,6 +64,17 @@ 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;
+       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_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 +149,7 @@ 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);
index 7194a51eb2174ee5867eebc01162aec42b9b4cf1..487c65b8cff0e79d5600da441c2ba12e8eb8c516 100644 (file)
@@ -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++)
@@ -885,6 +884,7 @@ 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;
@@ -3890,12 +3890,8 @@ 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);
-
-       if ((err = percpu_counter_init(&sbi->s_extent_cache_cnt, 0)) != 0) {
-               ext4_msg(sb, KERN_ERR, "insufficient memory");
+       if (ext4_es_register_shrinker(sbi))
                goto failed_mount3;
-       }
 
        sbi->s_stripe = ext4_get_stripe_size(sbi);
        sbi->s_extent_max_zeroout_kb = 32;
@@ -4225,10 +4221,9 @@ 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);
-       percpu_counter_destroy(&sbi->s_extent_cache_cnt);
        if (sbi->s_mmp_tsk)
                kthread_stop(sbi->s_mmp_tsk);
 failed_mount2:
index 849aaba75dc884d42f40e47103513d1dabe9fc97..ff4bd1b35246a33482b997d2093dbedbe6079357 100644 (file)
@@ -2450,6 +2450,37 @@ 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 */
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