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From: Peter Zijlstra <peterz@infradead.org>
To: Len Brown <lenb@kernel.org>
Cc: x86@kernel.org, linux-pm@vger.kernel.org,
	linux-kernel@vger.kernel.org, Len Brown <len.brown@intel.com>
Subject: Re: [PATCH] x86: Calculate MHz using APERF/MPERF for cpuinfo and scaling_cur_freq
Date: Fri, 1 Apr 2016 10:16:39 +0200	[thread overview]
Message-ID: <20160401081639.GD3448@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <52f711be59539723358bea1aa3c368910a68b46d.1459485198.git.len.brown@intel.com>

On Fri, Apr 01, 2016 at 12:37:00AM -0400, Len Brown wrote:
> From: Len Brown <len.brown@intel.com>
> 
> For x86 processors with APERF/MPERF and TSC,
> return meaningful and consistent MHz in
> /proc/cpuinfo and
> /sys/devices/system/cpu/cpu*/cpufreq/scaling_cur_freq
> 
> MHz is computed like so:
> 
> MHz = base_MHz * delta_APERF / delta_MPERF
> 
> MHz is the average frequency of the busy processor
> over a measurement interval.  The interval is
> defined to be the time between successive reads
> of the frequency on that processor, whether from
> /proc/cpuinfo or from sysfs cpufreq/scaling_cur_freq.
> As with previous methods of calculating MHz,
> idle time is excluded.

Is this really a semantic you want to pin down?

Since we're looking at doing something like:

lkml.kernel.org/r/20160303162829.GB6375@twins.programming.kicks-ass.net

We could also just return cpu_khz * whatever fraction we store there,
knowing it is something recent.

  parent reply	other threads:[~2016-04-01  8:16 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <6e0c25e64e0fb65a42dfc63ad5f660302e07cd87.1459485198.git.len.brown@intel.com>
2016-04-01  4:37 ` [PATCH] x86: Calculate MHz using APERF/MPERF for cpuinfo and scaling_cur_freq Len Brown
2016-04-01  7:56   ` [PATCH] x86: Calculate MHz using APERF/MPERF for cpuinfo and scaling_cur_freqy Thomas Gleixner
2016-04-01  8:03   ` [PATCH] x86: Calculate MHz using APERF/MPERF for cpuinfo and scaling_cur_freq Peter Zijlstra
2016-04-01  8:16     ` Stephane Gasparini
2016-04-01  8:23       ` Peter Zijlstra
2016-04-01  8:29         ` Peter Zijlstra
2016-04-01  9:30           ` Stephane Gasparini
2016-04-01  9:38             ` Peter Zijlstra
2016-04-01  9:50             ` Borislav Petkov
2016-04-02  5:22               ` Len Brown
2016-04-01  8:16   ` Peter Zijlstra [this message]
2016-04-24 16:38   ` Pavel Machek

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