On 2/21/2011 10:46 AM, Bill Holler wrote:
What are you asking for?
1) Forcing CPUs to run at the max performance?
Yes, I would like to force all CPUs to run at a fixed frequency which is
the highest available,
but I want to disable Turbo Mode (I can explain why). Technically I can
do it in BIOS,
but it is not our personal system, so we cannot reboot it any time we
want to run a test.
Currently the results we see are unstable and we thing the root of the
problem is in
dynamic CPU frequency. We use HW counters to get CPU cycles and then
transform the
number of CPU cycles to CPU Time, and this CPU Time shows unstable results.
On Linux I can set all CPUs at the frequency that is a little bit below
the max stock frequency
and this helps to stabilize the measurements and get [almost] maximum
performance.
Here is an example:
> On Linux (RHEL and OL) we can use a standard utility "cpufreq-selector"
> to set a fixed CPU frequency:
>
> [root@gabor nikm]# /usr/sbin/cpufreq-selector -c 0 -f 2267000
> ...
> [root@gabor nikm]# /usr/sbin/cpufreq-selector -c 15 -f 2267000
After that all CPUs run at 2.267 MHz while the max stock frequency is
2.27 MHz
2) Forcing some CPUs to run at a lower frequency to allow
other CPUs to run at the highest turbo bin (to game
benchmarks which only run on a sub-set of all CPUs)?
No, we need all CPUs to run at the same frequency.
If not these, then what is it?
If you want to do #2, then placing the "extra" CPUs in
the offline state will product the highest turbo mode
in the remaining CPUs running the benchmark.
Yes, right, but we are not trying to get the highest result, we develop
Oracle Solaris Studio Performance Analyzer tools, and we run performance
tests to verify that our profiling results are correct. For now we have
a known
problem with calculating CPU time from CPU cycles on systems that have
dynamic CPU frequency and Turbo Mode, but we want to verify that when
they use fixed frequency our results are correct.
Thanks.
Nik
----- Original Message -----
From: [email protected]
To: [email protected]
Sent: Saturday, February 19, 2011 2:10:37 PM GMT -08:00 US/Canada Pacific
Subject: [pm-discuss] How to change CPU frequency on Solaris?
We run performance tests on a Westmere system which has 16 CPUs.
SpeedStep and Turbo Mode are enabled in BIOS, so each CPU can use
a frequency within the "stock" range (1600 MHz - 2934 MHz) and above
(because of Turbo Mode).
On Linux (RHEL and OL) we can use a standard utility "cpufreq-selector"
to set a fixed CPU frequency:
[root@gabor nikm]# /usr/sbin/cpufreq-selector -c 0 -f 2261000
...
[root@gabor nikm]# /usr/sbin/cpufreq-selector -c 15 -f 2261000
Is there a way to change the CPU frequency on Solaris?
Thanks.
Nik
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