From: "Roger Pau Monné" <roger.pau@citrix.com>
To: Dario Faggioli <dfaggioli@suse.com>
Cc: Juergen Gross <jgross@suse.com>,
Charles Arnold <carnold@suse.com>,
Tomas Mozes <hydrapolic@gmail.com>, Glen <glenbarney@gmail.com>,
George Dunlap <george.dunlap@citrix.com>,
Jan Beulich <jbeulich@suse.com>, Sarah Newman <srn@prgmr.com>,
xen-devel@lists.xenproject.org
Subject: Re: [Xen-devel] [PATCH 0/2] xen: credit2: fix vcpu starvation due to too few credits
Date: Thu, 12 Mar 2020 16:08:52 +0100 [thread overview]
Message-ID: <20200312150852.GK24458@Air-de-Roger.citrite.net> (raw)
In-Reply-To: <158402056376.753.7091379488590272336.stgit@Palanthas>
Thanks for looking into this, seems like a specially tricky issue to
tackle!
On Thu, Mar 12, 2020 at 02:44:07PM +0100, Dario Faggioli wrote:
[...]
> For example, I have a trace showing that csched2_schedule() is invoked at
> t=57970746155ns. At t=57970747658ns (+1503ns) the s_timer is set to
> fire at t=57979485083ns, i.e., 8738928ns in future. That's because credit
> of snext is exactly that 8738928ns. Then, what I see is that the next
> call to burn_credits(), coming from csched2_schedule() for the same vCPU
> happens at t=60083283617ns. That is *a lot* (2103798534ns) later than
> when we expected and asked. Of course, that also means that delta is
> 2112537462ns, and therefore credits will sink to -2103798534!
Which timer does this hardware use? DYK if there's some relation
between the timer hardware used and the issue?
Thanks, Roger.
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next prev parent reply other threads:[~2020-03-12 15:09 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 ` Roger Pau Monné [this message]
2020-03-12 17:02 ` [Xen-devel] [PATCH 0/2] xen: credit2: fix vcpu starvation due to too few credits 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
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