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authorFilipe Manana <fdmanana@suse.com>2015-03-31 14:16:52 +0100
committerChris Mason <clm@fb.com>2015-06-10 07:02:43 -0700
commitb659ef027792219b590d67a2baf1643a93727d29 (patch)
tree648b746a44cbbdb2b27d17dc10513a87496d9b88 /fs/btrfs/file.c
parent1ab818b137e198e4d06e987a4b089411f2e39d40 (diff)
Btrfs: avoid syncing log in the fast fsync path when not necessary
Commit 3a8b36f37806 ("Btrfs: fix data loss in the fast fsync path") added a performance regression for that causes an unnecessary sync of the log trees (fs/subvol and root log trees) when 2 consecutive fsyncs are done against a file, without no writes or any metadata updates to the inode in between them and if a transaction is committed before the second fsync is called. Huang Ying reported this to lkml (https://lkml.org/lkml/2015/3/18/99) after a test sysbench test that measured a -62% decrease of file io requests per second for that tests' workload. The test is: echo performance > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor echo performance > /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor echo performance > /sys/devices/system/cpu/cpu2/cpufreq/scaling_governor echo performance > /sys/devices/system/cpu/cpu3/cpufreq/scaling_governor mkfs -t btrfs /dev/sda2 mount -t btrfs /dev/sda2 /fs/sda2 cd /fs/sda2 for ((i = 0; i < 1024; i++)); do fallocate -l 67108864 testfile.$i; done sysbench --test=fileio --max-requests=0 --num-threads=4 --max-time=600 \ --file-test-mode=rndwr --file-total-size=68719476736 --file-io-mode=sync \ --file-num=1024 run A test on kvm guest, running a debug kernel gave me the following results: Without 3a8b36f378060d: 16.01 reqs/sec With 3a8b36f378060d: 3.39 reqs/sec With 3a8b36f378060d and this patch: 16.04 reqs/sec Reported-by: Huang Ying <ying.huang@intel.com> Tested-by: Huang, Ying <ying.huang@intel.com> Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: Chris Mason <clm@fb.com>
Diffstat (limited to 'fs/btrfs/file.c')
-rw-r--r--fs/btrfs/file.c9
1 files changed, 6 insertions, 3 deletions
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index b072e17479aa..795d754327a7 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1868,6 +1868,7 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
struct btrfs_log_ctx ctx;
int ret = 0;
bool full_sync = 0;
+ const u64 len = end - start + 1;
trace_btrfs_sync_file(file, datasync);
@@ -1896,7 +1897,7 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
* all extents are persisted and the respective file extent
* items are in the fs/subvol btree.
*/
- ret = btrfs_wait_ordered_range(inode, start, end - start + 1);
+ ret = btrfs_wait_ordered_range(inode, start, len);
} else {
/*
* Start any new ordered operations before starting to log the
@@ -1968,8 +1969,10 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
*/
smp_mb();
if (btrfs_inode_in_log(inode, root->fs_info->generation) ||
- (full_sync && BTRFS_I(inode)->last_trans <=
- root->fs_info->last_trans_committed)) {
+ (BTRFS_I(inode)->last_trans <=
+ root->fs_info->last_trans_committed &&
+ (full_sync ||
+ !btrfs_have_ordered_extents_in_range(inode, start, len)))) {
/*
* We'v had everything committed since the last time we were
* modified so clear this flag in case it was set for whatever