Re: [Xen-devel] [PATCH 0/2] xen: credit2: fix vcpu starvation due to too few credits

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

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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