Thanks for the info Dirk. Basically I wanted to know whether the frequency of each of my multi-core chip can be changed individually (per-core DVFS) or the frequency can be changed on all cores simultaneously (chip wide DVFS). Based on cpufreq-info command's "CPUs which need to have their frequency coordinated by software" output as pointed by Viresh says that each core is individually controlled by software. Hence it is per-core DVFS. And it confirms with my experimental result also. But I got confused from "CPUs which run at the same hardware frequency" output which says both cores which mean chip-wide DVFS. Now I got cleared up as this has misleading values. Thanks for your insights. Regards, karthik On Wed, May 22, 2013 at 12:46 PM, Dirk Brandewie <dirk.brandewie@xxxxxxxxx> wrote: > 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. >> >> -- >> To unsubscribe from this list: send the line "unsubscribe cpufreq" in >> the body of a message to majordomo@xxxxxxxxxxxxxxx >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> > -- To unsubscribe from this list: send the line "unsubscribe cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
