From: Peter Zijlstra <peterz@infradead.org>
To: Stephane Gasparini <stephane.gasparini@linux.intel.com>
Cc: Len Brown <lenb@kernel.org>,
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 10:23:23 +0200 [thread overview]
Message-ID: <20160401082323.GE3448@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <9222CD56-C603-449C-A049-E518DAFA6883@linux.intel.com>
Trim your emails
On Fri, Apr 01, 2016 at 10:16:42AM +0200, Stephane Gasparini wrote:
> > That means these delta's can be arbitrarily large, in fact the MSRs can
> > have wrapped however many times.
>
> 64 bits is 18 446 744 073 709 551 615
>
> so even assuming a 10 GHz frequency if my math are good this is more than
> 58 years before the MSR wrap around, assuming the device ran always at max
> freq.
fair enough.. but going with 10Ghz, cpu_khz would be 10e6 ~ 33 bits,
which effectively reduces the wrap/overflow time to just 31 bits, which
per that frequency is just ~1/4th of a second.
next prev parent reply other threads:[~2016-04-01 8:23 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 [this message]
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
2016-04-24 16:38 ` Pavel Machek
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