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From: Tomasz Chmielewski <tch@virtall.com>
To: linux-btrfs@vger.kernel.org
Subject: Re: [REGRESSION] Super slow balance in v5.0-rc1
Date: Mon, 14 Jan 2019 20:47:14 +0900	[thread overview]
Message-ID: <7c6234aaeaf813400da5ff1e68f8c898@virtall.com> (raw)

> 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?

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).



# btrfs fi usage /data
WARNING: RAID56 detected, not implemented
WARNING: RAID56 detected, not implemented
Overall:
     Device size:                  14.47TiB
     Device allocated:            112.06GiB
     Device unallocated:           14.36TiB
     Device missing:                  0.00B
     Used:                        107.93GiB
     Free (estimated):                0.00B      (min: 8.00EiB)
     Data ratio:                       0.00
     Metadata ratio:                   1.64
     Global reserve:              512.00MiB      (used: 1.86MiB)

Data,RAID5: Size:5.28TiB, Used:3.04TiB
    /dev/sda5       1.76TiB
    /dev/sdb5       1.76TiB
    /dev/sdc5       1.76TiB
    /dev/sdd5       1.76TiB

Metadata,RAID1: Size:56.00GiB, Used:53.97GiB
    /dev/sda5      29.00GiB
    /dev/sdb5      27.00GiB
    /dev/sdc5      27.00GiB
    /dev/sdd5      29.00GiB

Metadata,RAID5: Size:12.38GiB, Used:11.13GiB
    /dev/sda5       4.12GiB
    /dev/sdb5       4.12GiB
    /dev/sdc5       4.12GiB
    /dev/sdd5       4.12GiB

System,RAID1: Size:32.00MiB, Used:416.00KiB
    /dev/sdb5      32.00MiB
    /dev/sdc5      32.00MiB

Unallocated:
    /dev/sda5       1.83TiB
    /dev/sdb5       1.83TiB
    /dev/sdc5       1.83TiB
    /dev/sdd5       1.83TiB


# btrfs balance status /data
Balance on '/data' is running
13 out of about 64 chunks balanced (15 considered),  80% left

             reply	other threads:[~2019-01-14 11:47 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-14 11:47 Tomasz Chmielewski [this message]
2019-01-14 12:34 ` [REGRESSION] Super slow balance in v5.0-rc1 Qu Wenruo
2019-01-14 13:06   ` Tomasz Chmielewski
  -- strict thread matches above, loose matches on Subject: below --
2019-01-14  5:39 Qu Wenruo
2019-01-14  9:35 ` David Sterba
2019-01-14 10:00   ` Qu Wenruo

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