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

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Date:   Wed, 14 Jun 2017 17:50:01 +0000
From:   "Liang, Kan" <kan.liang@...el.com>
To:     "Jiri Olsa (jolsa@...nel.org)" <jolsa@...nel.org>,
        "Arnaldo Carvalho de Melo" <acme@...nel.org>
CC:     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>,
        Jiri Olsa <jolsa@...nel.org>,
        "elliott@....com" <elliott@....com>,
        Andi Kleen <andi@...stfloor.org>
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