On 05/22/2013 09:28 AM, karthik vm wrote:
Hi Viresh,
Thanks for your quick reply. The output of cpufreq-info command is as below:
--------------------------------------------------------------------
$ cpufreq-info
cpufrequtils 007: cpufreq-info (C) Dominik Brodowski 2004-2009
Report errors and bugs to cpufreq@xxxxxxxxxxxxxxx, please.
analyzing CPU 0:
driver: acpi-cpufreq
CPUs which run at the same hardware frequency: 0 1
CPUs which need to have their frequency coordinated by software: 0
maximum transition latency: 10.0 us.
hardware limits: 1000 MHz - 2.00 GHz
available frequency steps: 2.00 GHz, 1.67 GHz, 1.33 GHz, 1000 MHz
available cpufreq governors: conservative, ondemand, userspace,
powersave, performance
current policy: frequency should be within 1000 MHz and 2.00 GHz.
The governor "ondemand" may decide which speed to use
within this range.
current CPU frequency is 2.00 GHz.
cpufreq stats: 2.00 GHz:7.39%, 1.67 GHz:0.66%, 1.33 GHz:1.23%, 1000
MHz:90.72% (48956)
analyzing CPU 1:
driver: acpi-cpufreq
CPUs which run at the same hardware frequency: 0 1
CPUs which need to have their frequency coordinated by software: 1
maximum transition latency: 10.0 us.
hardware limits: 1000 MHz - 2.00 GHz
available frequency steps: 2.00 GHz, 1.67 GHz, 1.33 GHz, 1000 MHz
available cpufreq governors: conservative, ondemand, userspace,
powersave, performance
current policy: frequency should be within 1000 MHz and 2.00 GHz.
The governor "ondemand" may decide which speed to use
within this range.
current CPU frequency is 2.00 GHz.
cpufreq stats: 2.00 GHz:5.87%, 1.67 GHz:0.22%, 1.33 GHz:0.35%, 1000
MHz:93.55% (10792)
----------------------------------------------------------------------------------
Also my current Linux version is 3.2.0-43-generic. May be thats why
there are misleading values for "CPUs which run at the same hardware
frequency".
Hence I guess that in my case "CPUs which run at the same hardware
frequency" & "CPUs which need to have their frequency coordinated by
software" should have the same value. If so this means that the CPU
has per-core DVFS. Please correct me if I am wrong.
cpufreq stats reports the frequency that was requested on each core.
The governor will request a frequency per core.
The actual frequency that the core/package runs at is coordinated by the
CPU itself based on the all the core requests.
There is no way (that I know of) to get the current frequency a given core is
running at.
Regards,
karthik
On Wed, May 22, 2013 at 12:08 AM, Viresh Kumar <viresh.kumar@xxxxxxxxxx> wrote:
On Tue, May 21, 2013 at 9:48 PM, karthik vm <meetvm@xxxxxxxxx> wrote:
I have few doubts on the DVFS capabilities of my intel Core2Duo
processor (T5750) which has 2 cores (no hyperthreading) and has
Enhanced Intel Speed Step Technology (EIST). When I run the
"cpufreq-info" command in Ubuntu Linux I get the result that: "CPUs
which run at the same hardware frequency: 0 1". Hence I assumed that
both the CPUs will increase and decrease the frequency in a
synchronous fashion.
But when I tried to verify it by using the below command:
$ watch -n 0.1 grep \"cpu MHz\" /proc/cpuinfo
Here I see that each core is varying the frequency individually
contrary to the cpufreq-info commands output that both run at the same
hardware frequency. Hence can anyone comment on this behavior?
Which kernel version are you using? Can you paste output of cpufreq-info.
You need to look at: "CPUs which need to have their frequency
coordinated by software:"
to get the right group of cpus..
The other group (pointed by you) had misleading values, which are
recently fixed in 3.9.
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