Bug 723416

Summary:	app-emulation/qemu-5.0.0 USE=io-uring causes memory leak and massive slowdown
Product:	Gentoo Linux	Reporter:	Bartosz Stebel <bartoszstebel>
Component:	Current packages	Assignee:	Matthias Maier <tamiko>
Status:	RESOLVED OBSOLETE
Severity:	major	CC:	alexander, can.ecodo.nu.n.o+bugs.gentoo, jaak, jasmin+gentoo, jstein, slyfox, virtualization
Priority:	Normal
Version:	unspecified
Hardware:	All
OS:	Linux
Whiteboard:
Package list:		Runtime testing required:	---

Description Bartosz Stebel 2020-05-16 17:00:47 UTC

Upstream bugs:
https://bugs.launchpad.net/qemu/+bug/1877716
https://bugs.launchpad.net/qemu/+bug/1873032
Upstream patch:
https://lists.gnu.org/archive/html/qemu-devel/2020-05/msg02728.html

It seems that Arch has blacklisted that option for now. I can confirm that building with USE=-io-uring fixes the problem.

Reproducible: Always

Comment 1 Ionen Wolkens gentoo-dev

2020-05-16 17:15:31 UTC

Gave me problems as well, maybe I did something wrong but couldn't manage to boot my usual VMs with aio=io_uring and just reverted to previous configs and turned it off for now.

I do hope this gets usable eventually given all the good uring press and qemu's heavy i/o usage, but masking the flag so people don't try what I did may be better for now -- not that I've tried the patch if that's something to consider adding to the ebuild.

Comment 2 Ionen Wolkens gentoo-dev

2020-12-10 02:20:48 UTC

This patch is present in 5.1.0, and given 5.0.0 isn't in tree anymore I think this issue can be closed.

And to update my previous comment, with qemu-5.2.0 being released decided to try io_uring again and having a much better experience (and actual noticeable performance increase).

Comment 3 Sergei Trofimovich (RETIRED) gentoo-dev

2020-12-13 12:14:43 UTC

Let's close it as obsolete.

Thank you!