linux-kernel - Re: Unified tracing buffer

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Message-ID: <48D94BA8.9030106@redhat.com>
Date:	Tue, 23 Sep 2008 16:03:52 -0400
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Mathieu Desnoyers <compudj@...stal.dyndns.org>,
	Martin Bligh <mbligh@...gle.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>, darren@...art.com,
	"Frank Ch. Eigler" <fche@...hat.com>,
	systemtap-ml <systemtap@...rces.redhat.com>
Subject: Re: Unified tracing buffer

Thomas Gleixner wrote:
> On Tue, 23 Sep 2008, Masami Hiramatsu wrote:
>> # cat /sys/devices/system/cpu/cpu0/cpuidle/state3/usage
>> 171210
> 
> C3 stops the TSC. So depending on how many C3 entries you have on the
> different cores, your TSCs will drift apart. Some BIOSes do even a
> lousy job trying to fixup the TSCs on exit from C3, which makes things
> even worse.
> 
>>     C1:                  type[C1] promotion[--] demotion[--] latency[001] usage[00000016] duration[00000000000000000000]
>>     C2:                  type[C2] promotion[--] demotion[--] latency[001] usage[00037969] duration[00000000000024288003]
>>     C3:                  type[C3] promotion[--] demotion[--] latency[057] usage[00171818] duration[00000000001881257636]
>>
>> Could these help you?
> 
> Yup, explains your TSC observation. Nothing we can do about. Broken by
> system design :( Welcome in the wonderful world of Inhell/BIOS/ACPI !

Thank you for analyzing! :-)
Hmm, then could I fix that by fixing my dsdt...?

Thanks again,

> 
> Thanks,
> 
> 	tglx

-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division

e-mail: mhiramat@...hat.com

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