Re: [REGRESSION] Super slow balance in v5.0-rc1

Tomasz Chmielewski
2019-01-14T13:06:31Z

On 2019-01-14 21:34, Qu Wenruo wrote:
> On 2019/1/14 下午7:47, Tomasz Chmielewski wrote:
>>> When rebasing my qgroup + balance optimization patches, I found one
>>> very
>>> obvious performance regression for balance.
>>>
>>> For normal 4G subvolume, 16 snapshots, balance workload, v4.20 kernel
>>> only takes 3s to relocate a metadata block group, while for v5.0-rc1,
>>> I
>>> don't really know how it will take as it hasn't finished yet.
>>
>> Are you sure it's v5.0-rc1 regression, not earlier?
>
> At least for what I'm describing, yes. v5.0-rc1 introduced bug, and
> already pinned down.
>
> So I'm afraid you're hitting another different bug.
>
>>
>> I'm trying to do a metadata-only balance from RAID-5 to RAID-1, with
>> 4.19.8.
>>
>> It was going relatively "normal", until it got stuck and showing no
>> progress.
>>
>> I've canceled the balance, upgraded to 4.20, started the balance
>> again.> For straight 11 days, it rewrote terabytes of data on the
>> disks, with no
>> progress at all.> Also, 4.19.8 had a balance interrupted because of
>> "out
>> of space", despite we have terabytes free.
>>
>> Metadata RAID-5 usage stays at 4.12GiB for the past 11 days (and a few
>> more days with 4.19.8).
>
> Are you using qgroup? Which is another huge cause of slow balance.

No, no qgroups.

# btrfs quota rescan /data
ERROR: quota rescan failed: Invalid argument