lkml.org 
[lkml]   [2009]   [Jan]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [Bug #12465] KVM guests stalling on 2.6.28 (bisected)

* Kevin Shanahan <kmshanah@ucwb.org.au> wrote:

> Running the ping test with without apache2 running in the guest:
>
> --- hermes-old.wumi.org.au ping statistics ---
> 900 packets transmitted, 900 received, 0% packet loss, time 902740ms
> rtt min/avg/max/mdev = 0.568/3.745/272.558/16.990 ms
>
> And with apache2 running:
>
> --- hermes-old.wumi.org.au ping statistics ---
> 900 packets transmitted, 900 received, 0% packet loss, time 902758ms
> rtt min/avg/max/mdev = 0.625/25.634/852.739/76.586 ms
>
> In both cases it's quite variable, but the max latency is still not as
> bad as when running with the irq chip enabled.

So the worst-case ping latency is more than 10 times lower?

I'd say this points in the direction of some sort of KVM-internal
wakeup/signalling latency that happens if KVM does not deschedule. For
example it could be a bug like this: if a guest image runs at 100% CPU
time for a long time, IRQ injections might not propagate up until the
preemption callbacks run. (but i'm just speculating here)

Ingo


\
 
 \ /
  Last update: 2009-01-20 19:45    [from the cache]
©2003-2011 Jasper Spaans