[Bug 1895487] Re: 'qemu-img convert' performance regression when target is a LVM volume
Chris MacNaughton
1895487 at bugs.launchpad.net
Mon Sep 14 07:28:14 UTC 2020
** Also affects: cloud-archive/stein
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1895487
Title:
'qemu-img convert' performance regression when target is a LVM volume
Status in Ubuntu Cloud Archive:
New
Status in Ubuntu Cloud Archive stein series:
New
Status in qemu package in Ubuntu:
Won't Fix
Bug description:
Running Ubuntu Server 18.04 with the Ubuntu Cloud Archive repository
on release 'bionic-updates/stein'
qemu-utils version 1:3.1+dfsg-2ubuntu3.7~cloud0
With bionic-updates/rocky and (stock bionic-updates) qemu-utils
version 1:2.11+dfsg-1ubuntu7.31, the following command takes ~35
seconds to complete:
# qemu-img convert -p -O raw -t none -f qcow2 some-qcow2.img
/dev/mapper/cinder--volumes-volume--9d18daa7--691c--44bc--b4c8--
a60cc70a435d
With bionic-updates/stein and qemu-utils version 1:3.1+dfsg-
2ubuntu3.7~cloud0, the same command does not progress visibly (-p
displays a rough percentage done), still displaying 0% finished after
two minutes.
Basic package level bisecting shows that qemu-utils version 1:4.0
+dfsg-0ubuntu9.8~cloud0 (from bionic-updates/train) fixes the
regression, behaving like 1:2.11+dfsg-1ubuntu7.31 again.
After verifying the bug also exists upstream, I bisected with the
following results:
- The bug was introduced with commit
34fa110e424e9a6a9b7e0274c3d4bfee766eb7ed (between v3.0.0-rc2 and rc3)
- The bug was fixed with commit
c9fdcf202f19fc2acdcb1ee0522ff5d61bf8c906 (between v3.1 and v4.0),
which is part of this patchset:
https://patchwork.kernel.org/cover/10865751/
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