[PATCH] ext4: count hits/misses of extent cache and expose in sysfs.

Vivek Haldar
2011-05-17T22:27:07Z

The number of hits and misses for each filesystem is exposed in
/sys/fs/ext4/<dev>/extent_cache_{hits, misses}.

Tested: fsstress, manual checks.
Signed-off-by: Vivek Haldar <haldar@google.com>
---
fs/ext4/ext4.h | 3 +++
fs/ext4/extents.c | 7 ++++++-
fs/ext4/super.c | 16 ++++++++++++++++
3 files changed, 25 insertions(+), 1 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 47986ae..9625b19 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1144,6 +1144,9 @@ struct ext4_sb_info {
unsigned long s_ext_blocks;
unsigned long s_ext_extents;
#endif
+ /* ext4 extent cache stats */
+ unsigned long extent_cache_hits;
+ unsigned long extent_cache_misses;

/* for buddy allocator */
struct ext4_group_info ***s_group_info;
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index e363f21..1ea440a 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -2035,6 +2035,7 @@ ext4_ext_in_cache(struct inode *inode, ext4_lblk_t block,
struct ext4_extent *ex)
{
struct ext4_ext_cache *cex;
+ struct ext4_sb_info *sbi;
int ret = 0;

/*
@@ -2042,6 +2043,7 @@ ext4_ext_in_cache(struct inode *inode, ext4_lblk_t block,
*/
spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
cex = &EXT4_I(inode)->i_cached_extent;
+ sbi = EXT4_SB(inode->i_sb);

/* has cache valid data? */
if (cex->ec_len == 0)
@@ -2057,6 +2059,10 @@ ext4_ext_in_cache(struct inode *inode, ext4_lblk_t block,
ret = 1;
}
errout:
+ if (!ret)
+ sbi->extent_cache_misses++;
+ else
+ sbi->extent_cache_hits++;
spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
return ret;
}
@@ -3900,4 +3906,3 @@ int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,

return error;
}
-
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index fc827bb..20cc98f 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2439,6 +2439,18 @@ static ssize_t lifetime_write_kbytes_show(struct ext4_attr *a,
EXT4_SB(sb)->s_sectors_written_start) >> 1)));
}

+static ssize_t extent_cache_hits_show(struct ext4_attr *a,
+ struct ext4_sb_info *sbi, char *buf)
+{
+ return snprintf(buf, PAGE_SIZE, "%lu\n", sbi->extent_cache_hits);
+}
+
+static ssize_t extent_cache_misses_show(struct ext4_attr *a,
+ struct ext4_sb_info *sbi, char *buf)
+{
+ return snprintf(buf, PAGE_SIZE, "%lu\n", sbi->extent_cache_misses);
+}
+
static ssize_t inode_readahead_blks_store(struct ext4_attr *a,
struct ext4_sb_info *sbi,
const char *buf, size_t count)
@@ -2496,6 +2508,8 @@ static struct ext4_attr ext4_attr_##name = __ATTR(name, mode, show, store)
EXT4_RO_ATTR(delayed_allocation_blocks);
EXT4_RO_ATTR(session_write_kbytes);
EXT4_RO_ATTR(lifetime_write_kbytes);
+EXT4_RO_ATTR(extent_cache_hits);
+EXT4_RO_ATTR(extent_cache_misses);
EXT4_ATTR_OFFSET(inode_readahead_blks, 0644, sbi_ui_show,
inode_readahead_blks_store, s_inode_readahead_blks);
EXT4_RW_ATTR_SBI_UI(inode_goal, s_inode_goal);
@@ -2511,6 +2525,8 @@ static struct attribute *ext4_attrs[] = {
ATTR_LIST(delayed_allocation_blocks),
ATTR_LIST(session_write_kbytes),
ATTR_LIST(lifetime_write_kbytes),
+ ATTR_LIST(extent_cache_hits),
+ ATTR_LIST(extent_cache_misses),
ATTR_LIST(inode_readahead_blks),
ATTR_LIST(inode_goal),
ATTR_LIST(mb_stats),
--
1.7.3.1