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| author | Yan, Zheng <zheng.z.yan@intel.com> | 2013-05-03 02:15:52 -0400 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2013-05-03 02:15:52 -0400 |
| commit | e30b5dca15dea86aa697f9d58ff646294fe80d3d (patch) | |
| tree | 549d1ff3f8e5ecb9675a2937113aa99e64ef3ea1 /fs/ext4/extents.c | |
| parent | 0d606e2c9fccdd4e67febf1e2da500e1bfe9e045 (diff) | |
| download | lwn-e30b5dca15dea86aa697f9d58ff646294fe80d3d.tar.gz lwn-e30b5dca15dea86aa697f9d58ff646294fe80d3d.zip | |
ext4: fix fio regression
We (Linux Kernel Performance project) found a regression introduced
by commit:
f7fec032aa ext4: track all extent status in extent status tree
The commit causes about 20% performance decrease in fio random write
test. Profiler shows that rb_next() uses a lot of CPU time. The call
stack is:
rb_next
ext4_es_find_delayed_extent
ext4_map_blocks
_ext4_get_block
ext4_get_block_write
__blockdev_direct_IO
ext4_direct_IO
generic_file_direct_write
__generic_file_aio_write
ext4_file_write
aio_rw_vect_retry
aio_run_iocb
do_io_submit
sys_io_submit
system_call_fastpath
io_submit
td_io_getevents
io_u_queued_complete
thread_main
main
__libc_start_main
The cause is that ext4_es_find_delayed_extent() doesn't have an
upper bound, it keeps searching until a delayed extent is found.
When there are a lots of non-delayed entries in the extent state
tree, ext4_es_find_delayed_extent() may uses a lot of CPU time.
Reported-by: LKP project <lkp@linux.intel.com>
Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Diffstat (limited to 'fs/ext4/extents.c')
| -rw-r--r-- | fs/ext4/extents.c | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index 107936db244e..bc0f1910b9cf 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -3642,7 +3642,7 @@ int ext4_find_delalloc_range(struct inode *inode, { struct extent_status es; - ext4_es_find_delayed_extent(inode, lblk_start, &es); + ext4_es_find_delayed_extent_range(inode, lblk_start, lblk_end, &es); if (es.es_len == 0) return 0; /* there is no delay extent in this tree */ else if (es.es_lblk <= lblk_start && @@ -4608,9 +4608,10 @@ static int ext4_find_delayed_extent(struct inode *inode, struct extent_status es; ext4_lblk_t block, next_del; - ext4_es_find_delayed_extent(inode, newes->es_lblk, &es); - if (newes->es_pblk == 0) { + ext4_es_find_delayed_extent_range(inode, newes->es_lblk, + newes->es_lblk + newes->es_len - 1, &es); + /* * No extent in extent-tree contains block @newes->es_pblk, * then the block may stay in 1)a hole or 2)delayed-extent. @@ -4630,7 +4631,7 @@ static int ext4_find_delayed_extent(struct inode *inode, } block = newes->es_lblk + newes->es_len; - ext4_es_find_delayed_extent(inode, block, &es); + ext4_es_find_delayed_extent_range(inode, block, EXT_MAX_BLOCKS, &es); if (es.es_len == 0) next_del = EXT_MAX_BLOCKS; else |