From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dirk Brandewie Subject: Re: Clarification on the DVFS capabilities Date: Wed, 22 May 2013 09:46:40 -0700 Message-ID: <519CF670.9030905@intel.com> References: Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:content-type:content-transfer-encoding; bh=6KcG0erwCwExpyyJFfkXez4qv9/XJaLt+tUqCdGkbU4=; b=UsAXG+Y2zjORAvegT5GBvN+MiPuaiayYZtSFMgcMyYTv12KmOtXtRER+0pMRuyNxdu w2LUNZ3rn5bomyeThIRFtTTG/yc6xLmfyQHu9TQxYuo3bs9EEKZj+v9PeGail0ZoixvN rHPXg2cb5qmK6CE/75/qiWGVgBunR0KNlRLqM26lfIN36vAR49J2QOiFAB6Wdsi2vRVA ABimF6iBpDVG+pWN8QH9H24WpHj16ofl6MqR7IdHDxpalIKq0gHWd9vm3GYvSTtv7MVO 901zXXwEIJkHq0Jah2KCJ+WsXgtwQpH8+Yd0oD/n7xnhCPRs8Kdr6+EOytAVvx64KBGD AmOQ== In-Reply-To: Sender: cpufreq-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: karthik vm Cc: Viresh Kumar , cpufreq 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@vger.kernel.org, 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 wrote: >> On Tue, May 21, 2013 at 9:48 PM, karthik vm 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@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >