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authorQu Wenruo <wqu@suse.com>2018-09-27 14:42:33 +0800
committerDavid Sterba <dsterba@suse.com>2018-10-15 17:23:36 +0200
commit2cd86d309bd1203241ceb833effe90787f3564a1 (patch)
treee4ed59844c55b5f2e9804400f41d7f2f776473fd /fs/btrfs/extent-tree.c
parent5f527822be40104e9056c981ff06c7750153a10a (diff)
downloadlinux-2cd86d309bd1203241ceb833effe90787f3564a1.tar.bz2
btrfs: qgroup: Don't trace subtree if we're dropping reloc tree
Reloc tree doesn't contribute to qgroup numbers, as we have accounted them at balance time (see replace_path()). Skipping the unneeded subtree tracing should reduce the overhead. [[Benchmark]] Hardware: VM 4G vRAM, 8 vCPUs, disk is using 'unsafe' cache mode, backing device is SAMSUNG 850 evo SSD. Host has 16G ram. Mkfs parameter: --nodesize 4K (To bump up tree size) Initial subvolume contents: 4G data copied from /usr and /lib. (With enough regular small files) Snapshots: 16 snapshots of the original subvolume. each snapshot has 3 random files modified. balance parameter: -m So the content should be pretty similar to a real world root fs layout. | v4.19-rc1 | w/ patchset | diff (*) --------------------------------------------------------------- relocated extents | 22929 | 22900 | -0.1% qgroup dirty extents | 227757 | 167139 | -26.6% time (sys) | 65.253s | 50.123s | -23.2% time (real) | 74.032s | 52.551s | -29.0% Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs/extent-tree.c')
-rw-r--r--fs/btrfs/extent-tree.c8
1 files changed, 7 insertions, 1 deletions
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 8798fa029ebe..d68ee91c00fc 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -8683,7 +8683,13 @@ skip:
parent = 0;
}
- if (need_account) {
+ /*
+ * Reloc tree doesn't contribute to qgroup numbers, and we have
+ * already accounted them at merge time (replace_path),
+ * thus we could skip expensive subtree trace here.
+ */
+ if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID &&
+ need_account) {
ret = btrfs_qgroup_trace_subtree(trans, next,
generation, level - 1);
if (ret) {