BMC/Intel-BMC/linux.git/fs/ext4/extents_status.h, branch dev

ext4: introduce aging to extent status tree

2014-11-25T16:55:24+00:00

Introduce a simple aging to extent status tree. Each extent has a REFERENCED bit which gets set when the extent is used. Shrinker then skips entries with referenced bit set and clears the bit. Thus frequently used extents have higher chances of staying in memory. Signed-off-by: Jan Kara Signed-off-by: Theodore Ts'o

ext4: cleanup flag definitions for extent status tree

2014-11-25T16:53:47+00:00

Currently flags for extent status tree are defined twice, once shifted and once without a being shifted. Consolidate these definitions into one place and make some computations automatic to make adding flags less error prone. Compiler should be clever enough to figure out these are constants and generate the same code. Signed-off-by: Jan Kara Signed-off-by: Theodore Ts'o

ext4: move handling of list of shrinkable inodes into extent status code

2014-11-25T16:49:25+00:00

Currently callers adding extents to extent status tree were responsible for adding the inode to the list of inodes with freeable extents. This is error prone and puts list handling in unnecessarily many places. Just add inode to the list automatically when the first non-delay extent is added to the tree and remove inode from the list when the last non-delay extent is removed. Signed-off-by: Jan Kara Signed-off-by: Theodore Ts'o

ext4: change LRU to round-robin in extent status tree shrinker

2014-11-25T16:45:37+00:00

In this commit we discard the lru algorithm for inodes with extent status tree because it takes significant effort to maintain a lru list in extent status tree shrinker and the shrinker can take a long time to scan this lru list in order to reclaim some objects. We replace the lru ordering with a simple round-robin. After that we never need to keep a lru list. That means that the list needn't be sorted if the shrinker can not reclaim any objects in the first round. Cc: Andreas Dilger Signed-off-by: Zheng Liu Signed-off-by: Jan Kara Signed-off-by: Theodore Ts'o

ext4: track extent status tree shrinker delay statictics

2014-09-02T02:26:49+00:00

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 Cc: Jan Kara Reviewed-by: Jan Kara Signed-off-by: Zheng Liu Signed-off-by: Theodore Ts'o

ext4: add ext4_es_store_pblock_status()

2014-02-20T01:15:15+00:00

Avoid false positives by static code analysis tools such as sparse and coverity caused by the fact that we set the physical block, and then the status in the extent_status structure. It is also more efficient to set both of these values at once. Addresses-Coverity-Id: #989077 Addresses-Coverity-Id: #989078 Addresses-Coverity-Id: #1080722 Signed-off-by: "Theodore Ts'o" Reviewed-by: Zheng Liu

ext4: isolate ext4_extents.h file

2013-08-28T18:47:06+00:00

After applied the commit (4a092d73), we have reduced the number of source files that need to #include ext4_extents.h. But we can do better. This commit defines ext4_zeroout_es() in extents.c and move EXT_MAX_BLOCKS into ext4.h in order not to include ext4_extents.h in indirect.c and ioctl.c. Meanwhile we just need to include this file in extent_status.c when ES_AGGRESSIVE_TEST is defined. Otherwise, this commit removes a duplicated declaration in trace/events/ext4.h. After applied this patch, we just need to include ext4_extents.h file in {super,migrate,move_extents,extents}.c, and it is easy for us to define a new extent disk layout. Signed-off-by: Zheng Liu Signed-off-by: "Theodore Ts'o"

ext4: cache all of an extent tree's leaf block upon reading

2013-08-17T01:23:41+00:00

When we read in an extent tree leaf block from disk, arrange to have all of its entries cached. In nearly all cases the in-memory representation will be more compact than the on-disk representation in the buffer cache, and it allows us to get the information without having to traverse the extent tree for successive extents. Signed-off-by: "Theodore Ts'o" Reviewed-by: Zheng Liu

ext4: use unsigned int for es_status values

2013-08-17T01:22:41+00:00

Don't use an unsigned long long for the es_status flags; this requires that we pass 64-bit values around which is painful on 32-bit systems. Instead pass the extent status flags around using the low 4 bits of an unsigned int, and shift them into place when we are reading or writing es_pblk. Signed-off-by: "Theodore Ts'o" Reviewed-by: Zheng Liu

ext4: improve extent cache shrink mechanism to avoid to burn CPU time

2013-07-01T12:12:37+00:00

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 Signed-off-by: Zheng Liu Signed-off-by: "Theodore Ts'o"