Commits
Qu Wenruo committed c4140cbf35b
btrfs: qgroup: Don't scan leaf if we're modifying reloc tree
Since reloc tree doesn't contribute to qgroup numbers, just skip them.
This should catch the final cause of unnecessary data ref processing
when running balance of metadata with qgroups on.
The 4G data 16 snapshots test (*) should explain it pretty well:
| delayed subtree | refactor delayed ref | this patch
---------------------------------------------------------------------
relocated | 22653 | 22673 | 22744
qgroup dirty | 122792 | 48360 | 70
time | 24.494 | 11.606 | 3.944
Finally, we're at the stage where qgroup + metadata balance cost no
obvious overhead.
Test environment:
Test VM:
- vRAM 8G
- vCPU 8
- block dev vitrio-blk, 'unsafe' cache mode
- host block 850evo
Test workload:
- Copy 4G data from /usr/ to one subvolume
- Create 16 snapshots of that subvolume, and modify 3 files in each
snapshot
- Enable quota, rescan
- Time "btrfs balance start -m"
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>