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>
		
	
			
		
			
				
	
	
		
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/*
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 *  fs/ext4/extents_status.h
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 *
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 * Written by Yongqiang Yang <xiaoqiangnk@gmail.com>
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 * Modified by
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 *	Allison Henderson <achender@linux.vnet.ibm.com>
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 *	Zheng Liu <wenqing.lz@taobao.com>
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 *
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 */
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#ifndef _EXT4_EXTENTS_STATUS_H
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#define _EXT4_EXTENTS_STATUS_H
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/*
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 * Turn on ES_DEBUG__ to get lots of info about extent status operations.
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 */
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#ifdef ES_DEBUG__
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#define es_debug(fmt, ...)	printk(fmt, ##__VA_ARGS__)
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#else
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#define es_debug(fmt, ...)	no_printk(fmt, ##__VA_ARGS__)
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#endif
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/*
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 * With ES_AGGRESSIVE_TEST defined, the result of es caching will be
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 * checked with old map_block's result.
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 */
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#define ES_AGGRESSIVE_TEST__
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/*
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 * These flags live in the high bits of extent_status.es_pblk
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 */
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#define ES_SHIFT	60
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#define EXTENT_STATUS_WRITTEN	(1 << 3)
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#define EXTENT_STATUS_UNWRITTEN (1 << 2)
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#define EXTENT_STATUS_DELAYED	(1 << 1)
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#define EXTENT_STATUS_HOLE	(1 << 0)
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#define EXTENT_STATUS_FLAGS	(EXTENT_STATUS_WRITTEN | \
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				 EXTENT_STATUS_UNWRITTEN | \
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				 EXTENT_STATUS_DELAYED | \
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				 EXTENT_STATUS_HOLE)
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#define ES_WRITTEN		(1ULL << 63)
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#define ES_UNWRITTEN		(1ULL << 62)
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#define ES_DELAYED		(1ULL << 61)
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#define ES_HOLE			(1ULL << 60)
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#define ES_MASK			(ES_WRITTEN | ES_UNWRITTEN | \
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				 ES_DELAYED | ES_HOLE)
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struct ext4_sb_info;
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struct ext4_extent;
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struct extent_status {
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	struct rb_node rb_node;
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	ext4_lblk_t es_lblk;	/* first logical block extent covers */
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	ext4_lblk_t es_len;	/* length of extent in block */
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	ext4_fsblk_t es_pblk;	/* first physical block */
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};
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struct ext4_es_tree {
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	struct rb_root root;
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	struct extent_status *cache_es;	/* recently accessed extent */
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};
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struct ext4_es_stats {
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	unsigned long es_stats_last_sorted;
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	unsigned long es_stats_shrunk;
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	unsigned long es_stats_cache_hits;
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	unsigned long es_stats_cache_misses;
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	u64 es_stats_scan_time;
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	u64 es_stats_max_scan_time;
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	struct percpu_counter es_stats_all_cnt;
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	struct percpu_counter es_stats_lru_cnt;
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};
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extern int __init ext4_init_es(void);
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extern void ext4_exit_es(void);
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extern void ext4_es_init_tree(struct ext4_es_tree *tree);
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extern int ext4_es_insert_extent(struct inode *inode, ext4_lblk_t lblk,
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				 ext4_lblk_t len, ext4_fsblk_t pblk,
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				 unsigned int status);
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extern void ext4_es_cache_extent(struct inode *inode, ext4_lblk_t lblk,
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				 ext4_lblk_t len, ext4_fsblk_t pblk,
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				 unsigned int status);
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extern int ext4_es_remove_extent(struct inode *inode, ext4_lblk_t lblk,
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				 ext4_lblk_t len);
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extern void ext4_es_find_delayed_extent_range(struct inode *inode,
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					ext4_lblk_t lblk, ext4_lblk_t end,
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					struct extent_status *es);
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extern int ext4_es_lookup_extent(struct inode *inode, ext4_lblk_t lblk,
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				 struct extent_status *es);
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static inline int ext4_es_is_written(struct extent_status *es)
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{
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	return (es->es_pblk & ES_WRITTEN) != 0;
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}
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static inline int ext4_es_is_unwritten(struct extent_status *es)
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{
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	return (es->es_pblk & ES_UNWRITTEN) != 0;
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}
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static inline int ext4_es_is_delayed(struct extent_status *es)
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{
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	return (es->es_pblk & ES_DELAYED) != 0;
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}
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static inline int ext4_es_is_hole(struct extent_status *es)
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{
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	return (es->es_pblk & ES_HOLE) != 0;
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}
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static inline unsigned int ext4_es_status(struct extent_status *es)
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{
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	return es->es_pblk >> ES_SHIFT;
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}
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static inline ext4_fsblk_t ext4_es_pblock(struct extent_status *es)
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{
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	return es->es_pblk & ~ES_MASK;
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}
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static inline void ext4_es_store_pblock(struct extent_status *es,
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					ext4_fsblk_t pb)
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{
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	ext4_fsblk_t block;
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	block = (pb & ~ES_MASK) | (es->es_pblk & ES_MASK);
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	es->es_pblk = block;
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}
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static inline void ext4_es_store_status(struct extent_status *es,
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					unsigned int status)
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{
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	es->es_pblk = (((ext4_fsblk_t)
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			(status & EXTENT_STATUS_FLAGS) << ES_SHIFT) |
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		       (es->es_pblk & ~ES_MASK));
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}
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static inline void ext4_es_store_pblock_status(struct extent_status *es,
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					       ext4_fsblk_t pb,
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					       unsigned int status)
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{
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	es->es_pblk = (((ext4_fsblk_t)
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			(status & EXTENT_STATUS_FLAGS) << ES_SHIFT) |
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		       (pb & ~ES_MASK));
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}
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extern int ext4_es_register_shrinker(struct ext4_sb_info *sbi);
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extern void ext4_es_unregister_shrinker(struct ext4_sb_info *sbi);
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extern void ext4_es_lru_add(struct inode *inode);
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extern void ext4_es_lru_del(struct inode *inode);
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#endif /* _EXT4_EXTENTS_STATUS_H */
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