From: Dario Faggioli <dfaggioli@suse.com>
To: "Andrew Cooper" <andrew.cooper3@citrix.com>,
"Jürgen Groß" <jgross@suse.com>,
xen-devel@lists.xenproject.org
Cc: Charles Arnold <carnold@suse.com>,
Jan Beulich <jbeulich@suse.com>, Glen <glenbarney@gmail.com>,
George Dunlap <george.dunlap@citrix.com>,
Tomas Mozes <hydrapolic@gmail.com>, Sarah Newman <srn@prgmr.com>
Subject: Re: [Xen-devel] [PATCH 0/2] xen: credit2: fix vcpu starvation due to too few credits
Date: Fri, 13 Mar 2020 08:26:40 +0100 [thread overview]
Message-ID: <a6084dc725aedd9c6e5e25b7ec56a5e23dac2ccc.camel@suse.com> (raw)
In-Reply-To: <a4bddd49-6a9a-6f66-9154-745d0648b42b@citrix.com>
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On Thu, 2020-03-12 at 16:27 +0000, Andrew Cooper wrote:
> On 12/03/2020 15:51, Jürgen Groß wrote:
> > - Could it be the vcpu is busy for very long time in the
> > hypervisor?
> > So either fighting with another vcpu for a lock, doing a long
> > running hypercall, ...
>
> Using watchdog=2 might catch that. (There is a counting issue which
> I've not had time to fix yet, which makes the watchdog more fragile
> with
> a smaller timeout, but 2 should be ok.)
>
Done (actually, I used "watchdog=1 watchdog_timeout=2"), both with and
without these patches applies.
I don't see any watchdog firing.
While I was there, I tried 1 too. Nothing either.
> > - The timer used is not reliable.
> >
> > - The time base is not reliable (tsc or whatever is used for
> > getting
> > the time has jumped 2 seconds into the future).
>
> Worth instrumenting the TSC rendezvous for unexpectedly large jumps?
>
Yes, we should look into that.
> > - System management mode has kicked in.
>
> There are non-architectural SMI_COUNT MSRs (0x34 on Intel, can't
> remember AMD off the top of my head) which can be used to see if any
> have occurred, and this has proved useful in the past for debugging.
>
I'll have to look up at how to check and dump these from where I need.
Let's see if I can do that... hints, code pointer or anything else you
may have handy would be much appreciated. :-)
Thanks and Regards
--
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
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prev parent reply other threads:[~2020-03-13 7:27 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-12 13:44 [Xen-devel] [PATCH 0/2] xen: credit2: fix vcpu starvation due to too few credits Dario Faggioli
2020-03-12 13:44 ` [Xen-devel] [PATCH 1/2] xen: credit2: avoid vCPUs to ever reach lower credits than idle Dario Faggioli
2020-03-12 13:55 ` Andrew Cooper
2020-03-12 14:40 ` George Dunlap
2020-03-12 15:10 ` Dario Faggioli
2020-03-12 14:58 ` Dario Faggioli
2020-03-12 14:45 ` George Dunlap
2020-03-12 17:03 ` Dario Faggioli
2020-03-12 15:26 ` Jan Beulich
2020-03-12 16:00 ` Jürgen Groß
2020-03-12 16:59 ` Dario Faggioli
2020-03-12 16:11 ` Dario Faggioli
2020-03-12 16:36 ` Jan Beulich
2020-03-12 13:44 ` [Xen-devel] [PATCH 2/2] xen: credit2: fix credit reset happening too few times Dario Faggioli
2020-03-12 15:08 ` [Xen-devel] [PATCH 0/2] xen: credit2: fix vcpu starvation due to too few credits Roger Pau Monné
2020-03-12 17:02 ` Dario Faggioli
2020-03-12 17:59 ` Roger Pau Monné
2020-03-13 6:19 ` Dario Faggioli
2020-03-12 15:51 ` Jürgen Groß
2020-03-12 16:27 ` Andrew Cooper
2020-03-13 7:26 ` Dario Faggioli [this message]
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