The performance governor for cpufreq doesn't seem to behave as advertised

mgoldshteyn · 08-23-2012, 01:53 PM

The kernel in use: 3.2.0-23-generic on Ubuntu 12.04LTS

For example, I issue the following command:

Code:

sudo cpufreq-set -c 0 -g performance

Then I go to /sys/devices/system/cpu/cpu0/cpufreq and type in the following:

Code:

sudo cat cpuinfo_cur_freq

Sometimes I get the max frequency (3600 MHz) when I do this and sometimes I get the min frequency (1600 MHz).

If I do:

Code:

cat scaling_governor

The output is performance, showing that the governor is in fact set to performance.

Then, to make it even more weird, if I do:

Code:

cpufreq-info

I get:

Code:

analyzing CPU 0:
  driver: acpi-cpufreq
  CPUs which run at the same hardware frequency: 0 1 2 3 8 9 10 11
  CPUs which need to have their frequency coordinated by software: 0
  maximum transition latency: 10.0 us.
  hardware limits: 1.60 GHz - 3.60 GHz
  available frequency steps: 3.60 GHz, 3.60 GHz, 3.47 GHz, 3.33 GHz, 3.20 GHz, 3.07 GHz, 2.93 GHz, 2.80 GHz, 2.67 GHz, 2.53 GHz, 2.40 GHz, 2.27 GHz, 2.13 GHz, 2.00 GHz, 1.87 GHz, 1.73 GHz, 1.60 GHz
  available cpufreq governors: conservative, ondemand, userspace, powersave, performance
  current policy: frequency should be within 3.60 GHz and 3.60 GHz.
                  The governor "performance" may decide which speed to use
                  within this range.
  current CPU frequency is 3.60 GHz.
...

If you look at the current policy above, you will notice that it is telling me that the CPU should be pegged at 3.60 GHz. Yet, polling (i.e., displaying) cpuinfo_cur_freq once a second seems to tell a different story.

byannoni · 08-23-2012, 02:03 PM

Try:

Code:

sudo cpufreq-set -c 0 -f 3600

mgoldshteyn · 08-23-2012, 02:10 PM

Quote:

Originally Posted by byannoni

Try:

Code:

sudo cpufreq-set -c 0 -f 3600

I tried this route as well and I just tried it again to be certain. I still get intermittent results with frequencies of 1.6 GHz and 3.6 GHz.

cpufreq-info reports:

Code:

analyzing CPU 0:
  driver: acpi-cpufreq
  CPUs which run at the same hardware frequency: 0 1 2 3 8 9 10 11
  CPUs which need to have their frequency coordinated by software: 0
  maximum transition latency: 10.0 us.
  hardware limits: 1.60 GHz - 3.60 GHz
  available frequency steps: 3.60 GHz, 3.60 GHz, 3.47 GHz, 3.33 GHz, 3.20 GHz, 3.07 GHz, 2.93 GHz, 2.80 GHz, 2.67 GHz, 2.53 GHz, 2.40 GHz, 2.27 GHz, 2.13 GHz, 2.00 GHz, 1.87 GHz, 1.73 GHz, 1.60 GHz
  available cpufreq governors: conservative, ondemand, userspace, powersave, performance
  current policy: frequency should be within 3.60 GHz and 3.60 GHz.
                  The governor "userspace" may decide which speed to use
                  within this range.
  current CPU frequency is 3.60 GHz.
  cpufreq stats: 3.60 GHz:83.88%, 3.60 GHz:16.12%, 3.47 GHz:0.00%, 3.33 GHz:0.00%, 3.20 GHz:0.00%, 3.07 GHz:0.00%, 2.93 GHz:0.00%, 2.80 GHz:0.00%, 2.67 GHz:0.00%, 2.53 GHz:0.00%, 2.40 GHz:0.00%, 2.27 GHz:0.00%, 2.13 GHz:0.00%, 2.00 GHz:0.00%, 1.87 GHz:0.00%, 1.73 GHz:0.00%, 1.60 GHz:0.00%  (2612)
...

Results:

Code:

/sys/devices/system/cpu/cpu0/cpufreq$ for i in {1..5}; do sudo cat cpuinfo_cur_freq; sleep 1; done
1600000
3600000
1600000
1600000
3600000

byannoni · 08-23-2012, 02:15 PM

Edit: Ignore this post.

mgoldshteyn · 08-23-2012, 02:16 PM

Quote:

Originally Posted by byannoni

Does it ever drop back down to 1600000? It is just going up there.

I just updated my previous reply with more data which indirectly answered this question. See above...

byannoni · 08-23-2012, 02:26 PM

Edit3: What is the output of these commands:

Code:

cat /proc/cpuinfo
lsmod | grep freq

mgoldshteyn · 08-23-2012, 02:35 PM

The architecture of the host in question is:

Dual X5687 @ 3.60GHz

So, 8 physical cores spread across two CPUs (16 virtual cores due to hyperthreading being turned on). EIST and C1E are turned on, all C states below 1 are turned off.

mgoldshteyn · 08-23-2012, 02:39 PM

Code:

lsmod | grep freq

No output

Code:

cat /proc/cpuinfo

produces the following for each of the 16 virtual CPUs:

Code:

processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 44
model name      : Intel(R) Xeon(R) CPU           X5687  @ 3.60GHz
stepping        : 2
microcode       : 0x14
cpu MHz         : 3601.000
cache size      : 12288 KB
physical id     : 0
siblings        : 8
core id         : 0
cpu cores       : 4
apicid          : 0
initial apicid  : 0
fpu             : yes
fpu_exception   : yes
cpuid level     : 11
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf pni dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid dca sse4_1 sse4_2 popcnt lahf_lm ida arat epb dts tpr_shadow vnmi flexpriority ept vpid
bogomips        : 7200.09
clflush size    : 64
cache_alignment : 64
address sizes   : 40 bits physical, 48 bits virtual
power management:

Out of desperation I also tried doing:

Code:

sudo modprobe speedstep-lib

This didn't change the behavior of frequencies changing...

In /lib/modules/3.2.0-23-generic/kernel/drivers/cpufreq, I have:

Code:

-rw-r--r-- 1 root root 11016 Apr 10 19:27 p4-clockmod.ko
-rw-r--r-- 1 root root 14112 Apr 10 19:27 pcc-cpufreq.ko
-rw-r--r-- 1 root root 10288 Apr 10 19:27 speedstep-lib.ko

Out of these only speedstep-lib is loadable as a module, but doesn't seem to change any of the perceived behavior.

byannoni · 08-23-2012, 07:06 PM

Try this:

Code:

sudo modprobe p4_clockmod

mgoldshteyn · 08-23-2012, 07:09 PM

Code:

sudo modprobe p4_clockmod

give me an error. Only speedstep-lib seems to work out of the three I listed.

byannoni · 08-23-2012, 07:11 PM

What error?

mgoldshteyn · 08-23-2012, 07:13 PM

Quote:

Originally Posted by byannoni

What error?

The exact message is:

Code:

FATAL: Error inserting p4_clockmod (/lib/modules/3.2.0-23-generic/kernel/drivers/cpufreq/p4-clockmod.ko):
Device or resource busy

byannoni · 08-23-2012, 07:17 PM

Try:

Code:

sudo rmmod speedstep-lib
sudo modprobe p4_clockmod

If that doesn't work, do this:

Code:

sudo /bin/echo "p4_clockmod" >> /etc/modules
sudo reboot

abrinister · 08-23-2012, 07:37 PM

Is the acpi-cpufreq daemon active? I modprobed this and my cpuinfo started registering my correct frequency setting.

Alex Brinister

---------- Post added 08-23-12 at 08:38 PM ----------

If you load the wrong module, it will give you that error. More here.

Alex Brinister

mgoldshteyn · 08-23-2012, 07:48 PM

Quote:

Originally Posted by abrinister

Is the acpi-cpufreq daemon active? I modprobed this and my cpuinfo started registering my correct frequency setting.

Yes, acpi-cpufreq is loaded. A quote from the original question (and reply #3), above:

Quote:

analyzing CPU 0:
driver: acpi-cpufreq
...

Although, perhaps strangely:

Code:

modinfo acpi-cpufreq

gives:

Code:

ERROR: modinfo: could not find module acpi-cpufreq

Just to be certain, I performed an:

Code:

su modprobe acpi-cpufreq

which completed silently, but modinfo still gives an error indicating that it could not find the module.