Re: [Bug #12465] KVM guests stalling on 2.6.28 (bisected)

Ingo Molnar
2009-01-20T16:06:13Z

* Kevin Shanahan <kmshanah-biM/RbsGxha6c6uEtOJ/EA@public.gmane.org> wrote:

> I've uploaded the debug info here:
> http://disenchant.net/tmp/bug-12465/

one interesting number to watch for is the KVM thread's wait_max in
/proc/*/sched. The largest one seems to be 11 milliseconds:

se.wait_max : 3.175034
se.wait_max : 4.029938
se.wait_max : 4.217674
se.wait_max : 4.957836
se.wait_max : 10.339471
se.wait_max : 11.603943

which would be about right given your latency settings:

/proc/sys/kernel/sched_latency_ns:
60000000

[ 60 msecs ]

but ... i dont specifically see the kvm threads there. Are they not in
/proc/*? Maybe it's in threads and it needs to be accessed via
/proc/*/task/*/sched, as via:

$ grep -h wait_max /proc/*/task/*/sched | sort -t: -n -k 2 | tail -10
se.wait_max : 77.858092
se.wait_max : 78.778409
se.wait_max : 79.379026
se.wait_max : 85.930963
se.wait_max : 87.671842
se.wait_max : 88.008602
se.wait_max : 95.095744
se.wait_max : 157.882573
se.wait_max : 268.714775
se.wait_max : 393.085252

so the worst-case latency

Btw., there's a few weird stats in your logs:

se.wait_max : -284.864857
se.wait_max : -284.843431
se.wait_max : -284.820204
se.wait_max : -284.345294
se.wait_max : -284.298462
se.wait_max : -284.018644
se.wait_max : -284.018070
se.wait_max : -188.022417
se.wait_max : -188.021659
se.wait_max : -92.030204
se.wait_max : -92.027877

that field is not supposed to be negative. Mike, Peter, any ideas?

Ingo