Hi Tharindu, Re: great effort, unfortunately what you mentioned does not verify the required fact (In other words, (1) your method requests the governor to do the frequency change request (FCR), (2) the governor ask the driver to do the job (trace the kernel code path, you will understand this). But internally, the CPU has single VID set, which request the motherboard regulator to change the Vcc. Motherboard (DC-to-DC) regulator does not have any way of setting different voltages for individual cores simultaneously. So, different core frequencies are not possible. However, (still I did not study the code), the scheduler might take the assigned frequency (by the user) into account when it schedule any task in the core (might be load balancing: to be confirmed) still no multiple frequencies are possible ). The informed frequency from sysfile is not accurate (the low lever drivers are not even called when you ask governor (sysfiles) to read the frequency): if you change the CPU frequency by other means (eg using writing directly to MSR), your sysfiles does not catch it. Have a look at low level implementation of frequency driver (they all change the frequency of the processor using MSR- a set of registers that specifically used to manage the CPU functionality and the configuration) So, if you want to verify that the CPU cores can stay in multiple frequencies simultaneously, the best method is to change the frequency by user-space governor and try to verify the frequency using direct MSRs (I did that and found which is not possible). If you can successfully show that, let me know. Sincerely, Pradeep M. Hettiarachchi On Thu, Jun 23, 2011 at 9:52 PM, Tharindu Rukshan Bamunuarachchi <btharindu@gmail.com> wrote:
Hi Pradeep,
Below commands will do the job.
modprobe acpi-cpufreq modprobe cpufreq_userspace
cd /sys/devices/system/cpu/cpu0/cpufreq echo userspace > scaling_governor echo 2394000 > scaling_setspeed
cd /sys/devices/system/cpu/cpu1/cpufreq echo userspace > scaling_governor echo 2128000 > scaling_setspeed
cd /sys/devices/system/cpu/cpu2/cpufreq echo userspace > scaling_governor echo 1862000 > scaling_setspeed
cd /sys/devices/system/cpu/cpu3/cpufreq echo userspace > scaling_governor echo 1596000 > scaling_setspeed
cat /proc/cpuinfo | grep MHz cpu MHz : 2394.000 cpu MHz : 2128.000 cpu MHz : 1862.000 cpu MHz : 1596.000
Tested on Q6600 quadcore:~ # cat /proc/cpuinfo | grep GHz model name : Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz model name : Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz model name : Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz model name : Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz
__ Tharindu "Rukshan" Bamunuarachchi
On Fri, Jun 24, 2011 at 3:17 AM, pradeep hettiarachchi <pacprnt@gmail.com> wrote:
Hi Tharindu,
An another round of the old questions:
Can you give me any evidence to confirm that the core frequencies can be run in different values from each other. You may try to do (set individual core frequency values) it individually through any governor or MSR methods. However, actually it does not implemented internally. Please show/tell me if you have any methods to show that core frequencies are different at any given time. (Take i7 950 or Q 6600 processors applicable approach so that I can verify it so easily)
Sincerely,
Pradeep M. Hettiarachchi
On Sat, Dec 25, 2010 at 2:45 PM, pradeep hettiarachchi <pacprnt@gmail.com> wrote:
Hi,
Here what I did: I set the "performance" governor for one of the cores and "ondemand" governor on an another core. Then I noticed that the cores have different frequencies. Based of the above observation on different processors, I have a couple of questions.
1) When I tried to frequency-scale in a core i7 processor, it allows me to set different governors for individual cores. As per to my understanding, the processor has 4 physical cores and 2 hardware threads per core. (totaling 8 cores altogether) This means, I should not be able to set different frequencies in two adjacent cores (say core 0 and core 1) as they both same hardware. My understanding is I should not be able to set the individual core frequencies as explained above.
2) When I played with Q6600 processor, I found that trough the governor, I can set the individual core-frequency. But as per to the literature, Intel does not provide a facility to frequency-scale in individual cores but the frequency in the entire processor.
3) What does the governor do? Does it set the frequency of the core directly ?
4) Is there any way that I can verify the actual frequency of a core other than the interface of the governor. Do you recommend to use MSR direly to change and measure the frequency of the system ?
Sincerely,
Pradeep M. Hettiarachchi