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authorYan, Zheng <zheng.z.yan@intel.com>2013-05-03 02:15:52 -0400
committerTheodore Ts'o <tytso@mit.edu>2013-05-03 02:15:52 -0400
commite30b5dca15dea86aa697f9d58ff646294fe80d3d (patch)
tree549d1ff3f8e5ecb9675a2937113aa99e64ef3ea1 /fs/ext4/extents_status.c
parent0d606e2c9fccdd4e67febf1e2da500e1bfe9e045 (diff)
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_status.c')
-rw-r--r--fs/ext4/extents_status.c17
1 files changed, 12 insertions, 5 deletions
diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
index fe3337a85ede..e6941e622d31 100644
--- a/fs/ext4/extents_status.c
+++ b/fs/ext4/extents_status.c
@@ -232,14 +232,16 @@ static struct extent_status *__es_tree_search(struct rb_root *root,
}
/*
- * ext4_es_find_delayed_extent: find the 1st delayed extent covering @es->lblk
- * if it exists, otherwise, the next extent after @es->lblk.
+ * ext4_es_find_delayed_extent_range: find the 1st delayed extent covering
+ * @es->lblk if it exists, otherwise, the next extent after @es->lblk.
*
* @inode: the inode which owns delayed extents
* @lblk: the offset where we start to search
+ * @end: the offset where we stop to search
* @es: delayed extent that we found
*/
-void ext4_es_find_delayed_extent(struct inode *inode, ext4_lblk_t lblk,
+void ext4_es_find_delayed_extent_range(struct inode *inode,
+ ext4_lblk_t lblk, ext4_lblk_t end,
struct extent_status *es)
{
struct ext4_es_tree *tree = NULL;
@@ -247,7 +249,8 @@ void ext4_es_find_delayed_extent(struct inode *inode, ext4_lblk_t lblk,
struct rb_node *node;
BUG_ON(es == NULL);
- trace_ext4_es_find_delayed_extent_enter(inode, lblk);
+ BUG_ON(end < lblk);
+ trace_ext4_es_find_delayed_extent_range_enter(inode, lblk);
read_lock(&EXT4_I(inode)->i_es_lock);
tree = &EXT4_I(inode)->i_es_tree;
@@ -270,6 +273,10 @@ out:
if (es1 && !ext4_es_is_delayed(es1)) {
while ((node = rb_next(&es1->rb_node)) != NULL) {
es1 = rb_entry(node, struct extent_status, rb_node);
+ if (es1->es_lblk > end) {
+ es1 = NULL;
+ break;
+ }
if (ext4_es_is_delayed(es1))
break;
}
@@ -285,7 +292,7 @@ out:
read_unlock(&EXT4_I(inode)->i_es_lock);
ext4_es_lru_add(inode);
- trace_ext4_es_find_delayed_extent_exit(inode, es);
+ trace_ext4_es_find_delayed_extent_range_exit(inode, es);
}
static struct extent_status *