linux-kernel - Re: [PATCH V2 0/2] measure SMI cost (user)

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Message-ID: <20170620202902.GI13640@kernel.org>
Date:   Tue, 20 Jun 2017 17:29:02 -0300
From:   'Arnaldo Carvalho de Melo' <acme@...nel.org>
To:     "Liang, Kan" <kan.liang@...el.com>
Cc:     "Jiri Olsa (jolsa@...nel.org)" <jolsa@...nel.org>,
        'Jiri Olsa' <jolsa@...hat.com>,
        'Peter Zijlstra' <peterz@...radead.org>,
        'Thomas Gleixner' <tglx@...utronix.de>,
        'Ingo Molnar' <mingo@...nel.org>,
        "'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>,
        'Stephane Eranian' <eranian@...gle.com>,
        "'elliott@....com'" <elliott@....com>,
        'Andi Kleen' <andi@...stfloor.org>
Subject: Re: [PATCH V2 0/2] measure SMI cost (user)

Em Tue, Jun 20, 2017 at 01:43:56PM +0000, Liang, Kan escreveu:
> Hi Arnaldo and Jirka,
> 
> Ping.
>> Any comments for the patch?

I thought there was a kernel part still outstanding, now I see it was
already merged, will try it and provide comments.

- Arnaldo
 
> Thanks,
> Kan 
> 
> > Subject: RE: [PATCH V2 0/2] measure SMI cost (user)
> > 
> > Hi Jirka,
> > 
> > Have you got a chance to try the code?
> > Are you OK with the patch?
> > 
> > Thanks,
> > Kan
> > 
> > >
> > > Em Fri, Jun 02, 2017 at 03:45:11PM +0000, Liang, Kan escreveu:
> > > > > > On Mon, May 29, 2017 at 02:52:39PM +0200, Peter Zijlstra wrote:
> > > > > > > On Mon, May 29, 2017 at 02:46:37PM +0200, Jiri Olsa wrote:
> > > > > > > > for some reason I can't get single SMI count generated, is
> > > > > > > > there a setup/bench that would provoke that?
> > >
> > > > > > > Not having SMIs is a good thing ;-) Not sure we can tickle
> > > > > > > them in a reliable way.
> > >
> > > > > > yea I saw some counts last time, now just zero so I was
> > > > > > wondering if it's working
> > >
> > > > > We have internal test case which can generate SMI, but I cannot
> > > > > publish the test case. Sorry about that.
> > >
> > > > APM_CNT (0xB2) could be used to trigger SMI#.
> > >
> > > Here if I run the following 'perf stat' command and press the mute
> > > button (the one sharing F1 in a thinkpad t450s it triggers SMIs,
> > > toggle it in quick sucession and it generates more, etc:
> > >
> > > [root@...et ~]# perf stat -I 1000 -e msr/smi/
> > > #           time             counts unit events
> > >      1.000103173                  0      msr/smi/
> > >      2.000278816                  4      msr/smi/
> > >      3.000472630                  4      msr/smi/
> > >      4.000743916                  0      msr/smi/
> > >      5.001369358                  4      msr/smi/
> > >      6.001668033                  0      msr/smi/
> > >      7.001852603                  4      msr/smi/
> > >      8.002108269                 12      msr/smi/
> > >      9.002367312                  0      msr/smi/
> > > ^C     9.961897866                  0      msr/smi/
> > >
> > > [root@...et ~]#
> > >
> > > - Arnaldo
> > >
> > > > It's documented in PCH datasheet.
> > > > https://www.intel.com/content/dam/www/public/us/en/
> > > > documents/datasheets/9-series-chipset-pch-datasheet.pdf
> > > >
> > > > APM_CNT-Advanced Power Management Control Port Register I/O
> > Address:
> > > > B2h
> > > > Attribute: R/W
> > > > Default Value: 00h
> > > > Size: 8 bits
> > > > Lockable: No
> > > > Usage: Legacy Only
> > > > Power Well: Core
> > > > Bit Description
> > > > 7:0 Used to pass an APM command between the OS and the SMI handler.
> > > > Writes to this port not only store data in the APMC register, but
> > > > also generates an SMI# when the APMC_EN bit is set.
> > > >
> > > > You can write a byte to port 0xB2 to trigger an SMI#
> > > >
> > > > Thanks,
> > > > Kan