Quoting Len Brown <lenb@xxxxxxxxxx>:
Sorry for disturbing, I am Tsafack Ghislain Landry, Ph.D. student at Ecole
Normale Superieure of Lyon, France. I have been trying to scale the
frequency
on my Intel E5506 Xeon processor via the cpufreq_acpi driver
unfortunately (I
have tested that feature using the following linux kernel versions : 2.6.32,
2.6.38, 2.6.39, 2.6.39.3, and 3.0.rc7). This a sample output
# cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq
2128000
#echo 1862000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed
# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed
1862000
# cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq
2128000
I have tried using the cpufreq-set util as well, but the result is the same.
bellow is the content of the /proc/acpi/processor/CPU0/info file. I was
wandering whether the "no" value of the parameters throttling
control, limit
interface can fully explain that behavior.
they are unrelated to this issue.
cat /proc/acpi/processor/CPU0/info
processor id: 0
acpi id: 1
bus mastering control: no
power management: yes
throttling control: no
limit interface: no
It is likely that you are obsering the effects of "hardware coordination."
Although Linux treats all the cores as independent, and even treats
HT threads as independent, they actually have dependencies.
In particular, all threads inside a package share the same voltage
regulator.
So in a package if one core asks to go fast and another asks to go slow,
the voltage will coordinated by hardware to support the most demanding
request. Since it is always a good idea to go at he maximum speed
suported by the available voltage, the cpu that requests slow will
also go fast, the same speed as his peer.
boot with "maxcpus=1" and try again -- or control the speeds
of the other threads on the system accordingly.
cheers,
-Len Brown, Intel Open Source Technology Center
Hi Brown,
Many thanks for your answer, you are right I got the problem fixed
booting with "maxcpus=1"
Regards,
Tsafack Landry
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