From mboxrd@z Thu Jan  1 00:00:00 1970
From: Steven Rostedt <rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org>
Subject: Re: [Bug #12465] KVM guests stalling on 2.6.28 (bisected)
Date: Tue, 20 Jan 2009 09:59:01 -0500 (EST)
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To: Ingo Molnar <mingo-X9Un+BFzKDI@public.gmane.org>
Cc: Kevin Shanahan <kmshanah-biM/RbsGxha6c6uEtOJ/EA@public.gmane.org>, Avi Kivity <avi-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, "Rafael J. Wysocki" <rjw-KKrjLPT3xs0@public.gmane.org>, Linux Kernel Mailing List <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Kernel Testers List <kernel-testers-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Kevin Shanahan <kmshanah-IiIpDuVlHfMLO379cgqW9odd74u8MsAO@public.gmane.org>, Mike Galbraith <efault-Mmb7MZpHnFY@public.gmane.org>, Peter Zijlstra <a.p.zijlstra-/NLkJaSkS4VmR6Xm/wNWPw@public.gmane.org>, =?ISO-8859-15?Q?Fr=E9d=E9ric_Weisbecker?= <fweisbec-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>



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.

-- Steve