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New Contributor III
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Intel Xeon Phi Per Core Frequency

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Hi All,

I have following system:

  • Operating System: CentOS Linux 7 (Core)
  • Kernel: Linux 3.10.0-514.10.2.el7.x86_64
  • Architecture: x86-64 Intel(R) Xeon Phi(TM) CPU 7210 @ 1.30GHz

Is the supported min and max frequency is 1GHz and 1.5GHz respectively?

I also observed that it's possible to set frequency of each core individually. I validated this by setting frequency of few cores to 1GHz and rest to default. Does that mean Xeon Phi has per core frequency DVFS?

Thanks.

Chetan Arvind Patil
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Black Belt
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The target frequency can be set on a per core basis, but I believe that you will find that all of the active cores always run at the same frequency.

"Dr. Bandwidth"

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Black Belt
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The target frequency can be set on a per core basis, but I believe that you will find that all of the active cores always run at the same frequency.

"Dr. Bandwidth"

View solution in original post

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New Contributor III
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Hi John,

Does that mean, in terms of architecture there is unified frequency control for all cores, not per core dynamic clock and voltage scaling (DCVS)?

One thing I have observed is that setting mix and max frequency doesn't seem to have any effect on the current frequency. Below is the log of cpu0 and it shows that current frequency is 1.2 GHz even though I set max and min to 1GHz. Any idea why this may be happening?

ls /sys/devices/system/cpu/cpu0/cpufreq/

affected_cpus                cpuinfo_transition_latency   scaling_governor
cpuinfo_cur_freq             related_cpus                 scaling_max_freq
cpuinfo_max_freq             scaling_available_governors  scaling_min_freq
cpuinfo_min_freq             scaling_driver               scaling_setspeed

sudo cat /sys/devices/system/cpu/cpu0/cpufreq/*
0
1219257
1500000
1000000
4294967295
0
performance powersave
intel_pstate
performance
1000000
1000000

 

Thanks.

Chetan Arvind Patil
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New Contributor I
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Hi
Probably you must use (on demand) instead (performance)
for dynamically frequency change  between (min) and (max) i don't use this hardware but
I think that it will be unable to him to work in his max frequency all the time
I don't know if management of dynamically range frequency of each cores are same on your
hardware,read subject information about the functionality of (governor)
if dynamically frequency is relative  with his temperature maybe, you can compile last
source (freeipmi-1.5.7)  for investigate more far.
Regards

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New Contributor III
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Hi,

The problem is that Xeon Phi doesn't have ondemand because it uses intel-pstate driver and not cpufreq. I can revert to cpufreq, but I don't know the reason for default intel-pstate and whether it's architecture dependent for Xeon Phi.

Refrence this blog post.

Thanks.

Chetan Arvind Patil
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New Contributor I
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Hi
he seems that you have (powersave) that is equivalent (ondemand)
Maybe if revert to cpufreq, you will evaluate exactly if this change is more effective
with your hardware used for answer your expectations.
The difference is very variable with different model hardware tested.
Regards

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New Contributor III
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Hi,

I think what I am asking has nothing to do with which governor is in use. It's hardware and architecture based. So, whatever Intel desigend at the circuit level will not change by a software.

Meaning, per core DVFS if supported has to be at the architecture level. I don't know why sysfs is giving ambiguous data.

Thanks.

Chetan Arvind Patil
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New Contributor I
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Hi
I don't share your reasoning   ,it's always the kernel and the system that have the  hand on all the
parameter and this management is above to all other elements ,if your request it's not propitious
for him, she will  be rejected.

About your comment;
(So, whatever Intel designed at the circuit level will not change by a software.)
it's false, he can be  temporary disabled or modulated by the system,and fortunately than its the case.
Here , now since two years and half  we work for reduce consumption and improve performance of the system
I can confirm to you that taking account  only reference based technical characteristic of hardware is
great error, the system make as that he want or can  make only.
The system is not exclusively reserved in his conception  to the Intel Hardware specificity unique
 even if his quality is currently probably the better..
After several hundred approach tested that give no result really significant we understand  now
where to operate,currently We obtain now a very very well results that are exceptional.
This improve is effective with hardware INTEL,AMD,ARM and PPC.
Currently we search how to solve without required recompile all the system differently,,with all process
that are situated in his level tree , this task seem not easy to make simple to solve.
I have find a solution that could be an shortcut but i am not yet certain it's operate correct.

About your second remarks:
If your order not answer correctly the problem is on side shared libraries where some process are locked.
You can test six dozen of models chipsets Intel different he will not change anything to this problem.
we referring to governor for evaluate approximately the part that are busy by the processors, but it's
not really an parameter very reliable.(more exactly ,how many time required for he decrease max to min)
I am not even certain that dynamic voltage scaling able to answer instantaneously or even change
progressively synchronized.

Regards

 

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New Contributor I
19 Views

Hi

I have read speedily an part his source..
I think you don't query sufficient resources for he could change value to 1.5 by himself and
return to 1.3 after the hot point of your task ended.
It's not exactly as that you want but you see already if change of frequency (turbo)  works.
Even if  frequency is low your hardware extremely power (as the truck instead the car )

About multi-cores (after having submit to  friends)
Even when you have standalone regulator each core the cost for driving each individually
would give result catastrophic. It's extremely complex, several problem exist .
Fortunately ,processors is only a part between the complete consumption of the hardware.

Regards

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