On Wed, 21 Jan 2009, Avi Kivity wrote: > Kevin Shanahan wrote: > > > > --- hermes-old.wumi.org.au ping statistics --- > > > > 900 packets transmitted, 900 received, 0% packet loss, time 899326ms > > > > rtt min/avg/max/mdev = 0.093/0.157/3.611/0.117 ms > > > > > > > > So, a _huge_ difference. But what does it mean? > > > > > > > It means, a scheduling problem. Can you run the latency tracer (which > > > only works with realtime priority), so we can tell if it is (a) kvm > > > failing to wake up the vcpu properly or (b) the scheduler delaying the > > > vcpu from running. > > > > > > > Sorry, but are you sure that's going to be useful? > > > > If it only works on realtime threads and I'm not seeing the problem when > > running kvm with realtime priority, is this going to tell you what you > > want to know? > > > > Not trying to be difficult, but that just didn't make sense to me. > > > > You're right, wasn't thinking properly. > > This is a tough one. I'll see if I can think of something. Ingo, any ideas? I fixed up the wakeup latency tracer to work with all tasks (as well as other fixes). You can checkout the following: git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace.git branch: tip/devel compile with CONFIG_FUNCTION_TRACER and CONFIG_SCHED_TRACER and just echo 0 > /debug/tracing/tracing_enabled echo wakeup > /debug/tracing/current_tracer echo 1 > /debug/tracing/tracing_enabled run your test echo 0 > /debug/tracing/tracing_enabled and then look at /debug/tracing/latency_trace -- Steve -- To unsubscribe from this list: send the line "unsubscribe kernel-testers" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
