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

Ingo Molnar
2009-01-20T15:04:08Z

* Steven Rostedt <rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org> wrote:

> On Tue, 20 Jan 2009, Ingo Molnar wrote:
> > Another test would be to build the scheduler latency tracer into your
> > kernel:
> >
> > CONFIG_SCHED_TRACER=y
> >
> > And enable it via:
> >
> > echo wakeup > /debug/tracing/current_tracer
> >
> > and you should be seeing the worst-case scheduling latency traces in
> > /debug/tracing/trace, and the largest observed latency will be in
> > /debug/tracing/tracing_max_latency [in microseconds].
>
> Note, the wakeup latency only tests realtime threads, since other
> threads can have other issues for wakeup. I could change the wakeup
> tracer as wakeup_rt, and make a new "wakeup" that tests all threads, but
> it may be difficult to get something accurate.

hm, that's a significant regression then. The latency tracer used to
measure the highest-prio task in the system - be that RT or non-rt.

Ingo