Date: Mon, 31 Aug 2015 10:38:21 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Borislav Petkov <bp@alien8.de>
Cc: Ingo Molnar <mingo@kernel.org>, Huang Rui <ray.huang@amd.com>,
        Borislav Petkov <bp@suse.de>, Jean Delvare <jdelvare@suse.de>,
        Guenter Roeck <linux@roeck-us.net>,
        Andy Lutomirski <luto@amacapital.net>,
        Andreas Herrmann <herrmann.der.user@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>, Len Brown <lenb@kernel.org>,
        John Stultz <john.stultz@linaro.org>,
        =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker <fweisbec@gmail.com>,
        lm-sensors@lm-sensors.org, linux-kernel@vger.kernel.org,
        x86@kernel.org, Andreas Herrmann <herrmann.der.user@googlemail.com>,
        Aravind Gopalakrishnan <Aravind.Gopalakrishnan@amd.com>,
        Fengguang Wu <fengguang.wu@intel.com>, Aaron Lu <aaron.lu@intel.com>,
        Tony Li <tony.li@amd.com>
Subject: Re: [PATCH 09/15] x86, amd: add accessor for number of cores per
 compute unit
Message-ID: <20150831083821.GE16853@twins.programming.kicks-ass.net>
References: <1440662866-28716-1-git-send-email-ray.huang@amd.com>
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 <20150828064814.GB20153@nazgul.tnic>
 <20150828080418.GB13309@gmail.com>
 <20150829091914.GA8878@gmail.com>
 <20150830155322.GA26370@nazgul.tnic>
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On Sun, Aug 30, 2015 at 05:53:22PM +0200, Borislav Petkov wrote:
> On Sat, Aug 29, 2015 at 11:19:14AM +0200, Ingo Molnar wrote:
> > So let me withdraw my ack: the much more important question that I
> > missed first time around, why is this reporting feature living in
> > hwmon, not in perf? We have energy reporting facilities in perf that
> > this should be synced to.
> 
> Because there's already fam15h_power driver which is exactly for that.
> Making it part of perf is then a question of cat-ting the same sysfs
> file twice, at the beginning and at the end of the trace, which is
> trivial.

That don't make sense.

Looking at the BKDG Fam 15h 60h-6Fh these MSRs are per compute unit.
This means you can do much finer grained measurements than system wide
-- which is all hwmon seems capable of.

Not to mention the proposed code is horrible, who in their right mind
does two rdmsrl_safe_on_cpu() back to back.


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