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| author |   Ethan Lien <ethanlien@synology.com> | 2018-05-17 14:58:29 +0800 |
|---|---|---|
| committer |   David Sterba <dsterba@suse.com> | 2018-05-30 16:46:53 +0200 |
| commit | 78d4295b1eeed4d857f11333caac8b4894ac4412 (patch) | |
| tree | 3f9af4c65fc9bad4ebc7209349eb510c16aa8916 /fs/btrfs | |
| parent | btrfs: Remove fs_info argument from btrfs_uuid_tree_rem (diff) | |
| download | linux-dev-78d4295b1eeed4d857f11333caac8b4894ac4412.tar.xz linux-dev-78d4295b1eeed4d857f11333caac8b4894ac4412.zip | |
btrfs: lift some btrfs_cross_ref_exist checks in nocow path
In nocow path, we check if the extent is snapshotted in
btrfs_cross_ref_exist(). We can do the similar check earlier and avoid
unnecessary search into extent tree.
A fio test on a Intel D-1531, 16GB RAM, SSD RAID-5 machine as follows:
[global]
group_reporting
time_based
thread=1
ioengine=libaio
bs=4k
iodepth=32
size=64G
runtime=180
numjobs=8
rw=randwrite
[file1]
filename=/mnt/nocow/testfile
IOPS result: unpatched patched
1 fio round: 46670 46958
snapshot
2 fio round: 51826 54498
3 fio round: 59767 61289
After snapshot, the first fio get about 5% performance gain. As we
continually write to the same file, all writes will resume to nocow mode
and eventually we have no performance gain.
Signed-off-by: Ethan Lien <ethanlien@synology.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ update comments ]
Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs')
| -rw-r--r-- | fs/btrfs/inode.c | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 5d370bbdf826..27293ff7174d 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -1370,6 +1370,13 @@ next_slot: btrfs_file_extent_encryption(leaf, fi) || btrfs_file_extent_other_encoding(leaf, fi)) goto out_check; + /* + * Do the same check as in btrfs_cross_ref_exist but + * without the unnecessary search. + */ + if (btrfs_file_extent_generation(leaf, fi) <= + btrfs_root_last_snapshot(&root->root_item)) + goto out_check; if (extent_type == BTRFS_FILE_EXTENT_REG && !force) goto out_check; if (btrfs_extent_readonly(fs_info, disk_bytenr)) @@ -7322,6 +7329,14 @@ noinline int can_nocow_extent(struct inode *inode, u64 offset, u64 *len, btrfs_file_extent_other_encoding(leaf, fi)) goto out; + /* + * Do the same check as in btrfs_cross_ref_exist but without the + * unnecessary search. + */ + if (btrfs_file_extent_generation(leaf, fi) <= + btrfs_root_last_snapshot(&root->root_item)) + goto out; + backref_offset = btrfs_file_extent_offset(leaf, fi); if (orig_start) { |