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Diffstat (limited to 'results/classifier/105/device/1877716')
| -rw-r--r-- | results/classifier/105/device/1877716 | 145 |
1 files changed, 145 insertions, 0 deletions
diff --git a/results/classifier/105/device/1877716 b/results/classifier/105/device/1877716 new file mode 100644 index 000000000..47149c0b5 --- /dev/null +++ b/results/classifier/105/device/1877716 @@ -0,0 +1,145 @@ +device: 0.952 +assembly: 0.946 +semantic: 0.943 +instruction: 0.921 +other: 0.918 +graphic: 0.893 +boot: 0.893 +KVM: 0.889 +mistranslation: 0.872 +socket: 0.870 +vnc: 0.862 +network: 0.819 + +Win10 guest unusable after a few minutes + +On Arch Linux, the recent qemu package update seems to misbehave on some systems. In my case, my Windows 10 guest runs fine for around 5 minutes and then start to get really sluggish, even unresponsive. It needs to be forced off. I could reproduce this on a minimal VM with no passthrough, although my current testing setup involves an nvme pcie passthrough. + +I bisected it to the following commit which rapidly starts to run sluggishly on my setup: +https://github.com/qemu/qemu/commit/73fd282e7b6dd4e4ea1c3bbb3d302c8db51e4ccf + +I've ran the previous commit ( https://github.com/qemu/qemu/commit/b321051cf48ccc2d3d832af111d688f2282f089b ) for the entire night without an issue so far. + +I believe this might be a duplicate of https://bugs.launchpad.net/qemu/+bug/1873032 , although I'm not sure. + +Linux cc 5.6.10-arch1-1 #1 SMP PREEMPT Sat, 02 May 2020 19:11:54 +0000 x86_64 GNU/Linux +AMD Ryzen 7 2700X Eight-Core Processor + + + +Note that bisecting is difficult due to the nature of the bug (does not appear before 5 to 10 minutes on my machine). + + + +I can also replicate the problem on current master. I can solve it by building master with --disable-linux-io-uring. + +I also tried building Linux 5.4.39 where the issue happens too: +Linux cc 5.4.39qemu #1 SMP PREEMPT Sat May 9 12:11:38 CEST 2020 x86_64 GNU/Linux + +I attached the logs of that latest run. + +On Sat, May 9, 2020 at 9:16 AM Xavier <email address hidden> wrote: +> +> Public bug reported: +> +> On Arch Linux, the recent qemu package update seems to misbehave on some +> systems. In my case, my Windows 10 guest runs fine for around 5 minutes +> and then start to get really sluggish, even unresponsive. It needs to be +> forced off. I could reproduce this on a minimal VM with no passthrough, +> although my current testing setup involves an nvme pcie passthrough. +> +> I bisected it to the following commit which rapidly starts to run sluggishly on my setup: +> https://github.com/qemu/qemu/commit/73fd282e7b6dd4e4ea1c3bbb3d302c8db51e4ccf + +Thanks for bisecting this bug! Arch Linux can work around it in the +short term by building with ./configure --disable-linux-io-uring +and/or removing the liburing build dependency. + +I will try to reproduce the issue and send a QEMU patch to fix it. + + +On Mon, May 11, 2020 at 10:12 AM Stefan Hajnoczi <email address hidden> wrote: +> On Sat, May 9, 2020 at 9:16 AM Xavier <email address hidden> wrote: +> > +> > Public bug reported: +> > +> > On Arch Linux, the recent qemu package update seems to misbehave on some +> > systems. In my case, my Windows 10 guest runs fine for around 5 minutes +> > and then start to get really sluggish, even unresponsive. It needs to be +> > forced off. I could reproduce this on a minimal VM with no passthrough, +> > although my current testing setup involves an nvme pcie passthrough. +> > +> > I bisected it to the following commit which rapidly starts to run sluggishly on my setup: +> > https://github.com/qemu/qemu/commit/73fd282e7b6dd4e4ea1c3bbb3d302c8db51e4ccf +> +> Thanks for bisecting this bug! Arch Linux can work around it in the +> short term by building with ./configure --disable-linux-io-uring +> and/or removing the liburing build dependency. + +Hmm...a brief look at the Arch Linux package source suggests QEMU is +not being built with io_uring enabled. Anatol, please confirm whether +this is correct. + +If io_uring is not enabled then this bug may affect most existing +users on Linux. Initially I thought it was because Arch Linux had +enabled the new io_uring feature but I was probably mistaken. + + +Stefan, + +Arch explicitly disabled io_uring for qemu after discovering this bug. That's why you don't see it enabled in the recent version. + +5.0.0-6 doesn't have io_uring enabled. +5.0.0-5 does have it, and you can grab it here: [1]. + +[1] https://archive.archlinux.org/packages/q/qemu/qemu-5.0.0-5-x86_64.pkg.tar.zst + +As of version 5.0.0-6 (released a day ago), qemu on Arch is no longer built with io_uring support because of this bug. The previous version (5.0.0-5) was built with io_uring support and this bug was happening on my machine. Before the fixed version was released I myself added --disable-linux-io-uring to the build file of 5.0.0-5 and that fixed the issue for me. Now I'm running 5.0.0-6 and it's working as good as ever. +You can track the changes of qemu build files here: https://git.archlinux.org/svntogit/packages.git/log/trunk?h=packages/qemu + +That's good news! Most users do not have io_uring enabled yet. + +I have been able to reproduce the issue and found that nodes are not being removed from the AioContext->aio_handlers list when aio_set_fd_handler() is called. perf shows that large amounts of CPU time are spent in aio_pending(). + +Working on getting to the bottom of the issue and fixing it. + +Thank you Stefan for looking at this issue. + +As Alexander and @postfactum mentioned Arch disabled io_uring feature after this bug has been discovered. Here is an Arch Linux issue that tracks it https://bugs.archlinux.org/task/66578 + +Please try this patch series: +https://lists.gnu.org/archive/html/qemu-devel/2020-05/msg02728.html + +Unofficial x86_64 build of v5.0.0 with those 2 patches for Arch is here: [1]. + +[1] https://download.opensuse.org/repositories/home:/post-factum/Arch/x86_64/ + +Hi Stefan, + +I applied your series on top of master with io_uring enabled and I no longer experience the issue. Let me know if you need additional testing. + +Thank you for fixing this so promptly. + +On Tue, May 12, 2020, 16:25 zkrx <email address hidden> wrote: + +> Hi Stefan, +> +> I applied your series on top of master with io_uring enabled and I no +> longer experience the issue. Let me know if you need additional testing. +> +> Thank you for fixing this so promptly. +> + +That's great! Thanks for your bug report and time investigating this issue. + +Stefan + +> + + +Thank you Stefan for the fixes. Once these patches land the upstream repo I'll pull it into the Arch package and reenable io_uring. + +The fix has been merged: +https://git.qemu.org/?p=qemu.git;a=commit;h=f2465433b43fb87766d79f42191607dac4aed5b4 + + |