From: bugzilla-daemon@bugzilla.kernel.org
To: kvm@vger.kernel.org
Subject: [Bug 199727] CPU freezes in KVM guests during high IO load on host
Date: Sat, 21 Aug 2021 08:53:17 +0000 [thread overview]
Message-ID: <bug-199727-28872-4DPBhqZpKu@https.bugzilla.kernel.org/> (raw)
In-Reply-To: <bug-199727-28872@https.bugzilla.kernel.org/>
https://bugzilla.kernel.org/show_bug.cgi?id=199727
--- Comment #3 from Roland Kletzing (devzero@web.de) ---
i had a look at kvm process with strace.
with virtual disk caching option set to "Default (no cache)", kvm is doing IO
submission via io_submit() instead of pwritev(), and apparently that can be a
long blocking call.
i see whenever the VM getting hickup and pingtime goes through the roof, there
is long blocking io_submit() operation in progress
looks like a "design issue" to me and "Default (no cache)" thus being a bad
default setting.
see:
https://lwn.net/Articles/508064/
and
https://stackoverflow.com/questions/34572559/asynchronous-io-io-submit-latency-in-ubuntu-linux
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next prev parent reply other threads:[~2021-08-21 8:53 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <bug-199727-28872@https.bugzilla.kernel.org/>
2021-08-20 17:25 ` [Bug 199727] CPU freezes in KVM guests during high IO load on host bugzilla-daemon
2021-08-21 8:53 ` bugzilla-daemon [this message]
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