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Now we maintain an proper in-order LRU list in ext4 to reclaim entries
from extent status tree when we are under heavy memory pressure. For
keeping this order, a spin lock is used to protect this list. But this
lock burns a lot of CPU time. We can use the following steps to trigger
it.
% cd /dev/shm
% dd if=/dev/zero of=ext4-img bs=1M count=2k
% mkfs.ext4 ext4-img
% mount -t ext4 -o loop ext4-img /mnt
% cd /mnt
% for ((i=0;i<160;i++)); do truncate -s 64g $i; done
% for ((i=0;i<160;i++)); do cp $i /dev/null &; done
% perf record -a -g
% perf report
This commit tries to fix this problem. Now a new member called
i_touch_when is added into ext4_inode_info to record the last access
time for an inode. Meanwhile we never need to keep a proper in-order
LRU list. So this can avoid to burns some CPU time. When we try to
reclaim some entries from extent status tree, we use list_sort() to get
a proper in-order list. Then we traverse this list to discard some
entries. In ext4_sb_info, we use s_es_last_sorted to record the last
time of sorting this list. When we traverse the list, we skip the inode
that is newer than this time, and move this inode to the tail of LRU
list. When the head of the list is newer than s_es_last_sorted, we will
sort the LRU list again.
In this commit, we break the loop if s_extent_cache_cnt == 0 because
that means that all extents in extent status tree have been reclaimed.
Meanwhile in this commit, ext4_es_{un}register_shrinker()'s prototype is
changed to save a local variable in these functions.
Reported-by: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
129 lines
3.4 KiB
C
129 lines
3.4 KiB
C
/*
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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 EXTENT_STATUS_WRITTEN (1ULL << 63)
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#define EXTENT_STATUS_UNWRITTEN (1ULL << 62)
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#define EXTENT_STATUS_DELAYED (1ULL << 61)
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#define EXTENT_STATUS_HOLE (1ULL << 60)
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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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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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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 long long 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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extern int ext4_es_zeroout(struct inode *inode, struct ext4_extent *ex);
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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 & EXTENT_STATUS_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 & EXTENT_STATUS_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 & EXTENT_STATUS_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 & EXTENT_STATUS_HOLE) != 0;
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}
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static inline ext4_fsblk_t ext4_es_status(struct extent_status *es)
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{
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return (es->es_pblk & EXTENT_STATUS_FLAGS);
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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 & ~EXTENT_STATUS_FLAGS);
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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 & ~EXTENT_STATUS_FLAGS) |
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(es->es_pblk & EXTENT_STATUS_FLAGS);
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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 long long status)
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{
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ext4_fsblk_t block;
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block = (status & EXTENT_STATUS_FLAGS) |
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(es->es_pblk & ~EXTENT_STATUS_FLAGS);
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es->es_pblk = block;
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}
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extern void 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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