linux-kernel - Re: 50 Watt idle power regression bisected to Linux-3.10

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Date:	Tue, 10 Dec 2013 16:06:56 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Mike Galbraith <bitbucket@...ine.de>, Len Brown <lenb@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jeremy Eder <jeder@...hat.com>, x86@...nel.org
Subject: Re: 50 Watt idle power regression bisected to Linux-3.10


* Thomas Gleixner <tglx@...utronix.de> wrote:

> On Tue, 10 Dec 2013, Mike Galbraith wrote:
> > vogelweide:~/:[130]# turbostat -P -i 60
> > pk cor CPU    %c0  GHz  TSC SMI    %c1    %c3    %c6 CTMP   %pc3   %pc6
> >              0.02 2.12 2.26   0  43.40  56.57   0.00   53  33.81   0.00
> >  0   0   0   0.23 2.10 2.26   5  65.47  34.30   0.00   52  10.69   0.00
> 
> ...
>  
> > That, vs solid >99% pc3 for old 3.0 enterprise kernel.  What happened,
> > dunno, kernel called itself master.  Whatever, I don't like test bogons,
> > and this is one, so I thought I should let you know.  DL980 refuses to
> > come close to the previous result.
> 
> Hmm, that's very similar to the issue Len is seing on his quad 
> socket WM.
> 
> But I can't see it on my dual socket SNB, neither does PeterZ on his 
> dual socket WM machine. Heisenbugs ....
> 
> Can you offline all cpus except core 0, enable all trace events (nop 
> tracer), run "sleep 100" and stop and grab the trace? Please make 
> sure that your tracebuffer is big enough to cover the full thing.

I guess because we are facing a Heisenbug it might be prudent to check 
that the bug is still present with all those cpus offlined and with 
tracing enabled :-/

Thanks,

	Ingo
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