linux-kernel - Re: [REDO PATCH v7] perf/x86/amd/power: Add AMD accumulated power reporting mechanism

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Date:	Fri, 17 Jun 2016 18:03:07 +0800
From:	Huang Rui <ray.huang@....com>
To:	Vince Weaver <vincent.weaver@...ne.edu>
CC:	Borislav Petkov <bp@...e.de>, Thomas Gleixner <tglx@...utronix.de>,
	"Peter Zijlstra" <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	"Andy Lutomirski" <luto@...capital.net>,
	Robert Richter <rric@...nel.org>,
	"Jacob Shin" <jacob.w.shin@...il.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Kan Liang <kan.liang@...el.com>,
	<linux-kernel@...r.kernel.org>, <x86@...nel.org>,
	Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
	Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com>,
	Borislav Petkov <bp@...en8.de>,
	Guenter Roeck <linux@...ck-us.net>,
	Fengguang Wu <fengguang.wu@...el.com>
Subject: Re: [REDO PATCH v7] perf/x86/amd/power: Add AMD accumulated power
 reporting mechanism

On Thu, Jun 16, 2016 at 04:44:20PM -0400, Vince Weaver wrote:
> On Thu, 16 Jun 2016, Huang Rui wrote:
> 
> > > 1.  In theory this should also work on an amd fam16h model 30h
> > >     processor too, correct?  The current code limits things to fam15h
> > >     even though the fam16mod30h has all the proper cpuid flags.
> > > 
> > 
> > I was told this feature would be supported on fam15h 60h, 70h and
> > later processors before. Just checked the fam16h model 30h BKDG, yes,
> > it should be also supported. But I didn't test that platform, if you
> > confirm it works in your side. We can enable it.
> 
> I can confirm I get power readings on my fam16hmod30h board once I apply a 
> trivial patch to the driver.  I'll send the patch in a separate e-mail.
> 

OK, thanks.

> > PTSC's frequency is about 100Mhz, it shouldn't be overflow.
> 
> That's what I thought.  I'm trying to read the value using the /dev/msr 
> interface from userspace and I get weird results.
> 
> i.e.:
> 	Jx: read 62d299b84
> 	PTSC MSR: read 72fe92
> 	
> 	sleep 5ms
> 
> 	Jy: read 631b453b9
> 	PTSC MSR: read 46b25
> 
> this happens about half the time (PTSC going backwards).  Though 
> admittedly the problem could somehow be in the MSR code I'm using.
> 

Can you try to read the MSR value two times with the same core
(rdmsrl_on_cpu)?

Thanks,
Rui