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

Qu Wenruo
2019-01-14T05:39:59Z

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Hi,

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.

And the most important part is, this happens when quota is *DISABLED*!!!

I'm bisecting for this regression, but if there are some users trying
latest rc kernel, please be aware of this regression.