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View Full Version : cpuspeed is a killer



gthill
1st August 2007, 03:38 PM
I noticed that cpuspeed is really killing the performance of 4 of the 5 fedora7 machines that I have access to. When I do a cat /proc/cpuinfo the results are way below what i was expecting.
Here is an example from my amd 5600 dual core.


[root@tc2 ~]# cat /proc/cpuinfo
processor : 0
vendor_id : AuthenticAMD
cpu family : 15
model : 67
model name : AMD Athlon(tm) 64 X2 Dual Core Processor 5600+
stepping : 3
cpu MHz : 1000.000
cache size : 1024 KB
physical id : 0
siblings : 2
core id : 0
cpu cores : 2
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 1
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt rdtscp lm 3dnowext 3dnow pni cx16 lahf_lm cmp_legacy svm extapic cr8legacy ts fid vid ttp tm stc
bogomips : 2005.40
clflush size : 64

processor : 1
vendor_id : AuthenticAMD
cpu family : 15
model : 67
model name : AMD Athlon(tm) 64 X2 Dual Core Processor 5600+
stepping : 3
cpu MHz : 1000.000
cache size : 1024 KB
physical id : 0
siblings : 2
core id : 1
cpu cores : 2
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 1
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt rdtscp lm 3dnowext 3dnow pni cx16 lahf_lm cmp_legacy svm extapic cr8legacy ts fid vid ttp tm stc
bogomips : 2005.40
clflush size : 64

[root@tc2 ~]# service cpuspeed stop
Disabling ondemand cpu frequency scaling: [ OK ]
[root@tc2 ~]# cat /proc/cpuinfo
processor : 0
vendor_id : AuthenticAMD
cpu family : 15
model : 67
model name : AMD Athlon(tm) 64 X2 Dual Core Processor 5600+
stepping : 3
cpu MHz : 2800.000
cache size : 1024 KB
physical id : 0
siblings : 2
core id : 0
cpu cores : 2
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 1
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt rdtscp lm 3dnowext 3dnow pni cx16 lahf_lm cmp_legacy svm extapic cr8legacy ts fid vid ttp tm stc
bogomips : 5615.12
clflush size : 64

processor : 1
vendor_id : AuthenticAMD
cpu family : 15
model : 67
model name : AMD Athlon(tm) 64 X2 Dual Core Processor 5600+
stepping : 3
cpu MHz : 2800.000
cache size : 1024 KB
physical id : 0
siblings : 2
core id : 1
cpu cores : 2
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 1
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt rdtscp lm 3dnowext 3dnow pni cx16 lahf_lm cmp_legacy svm extapic cr8legacy ts fid vid ttp tm stc
bogomips : 5615.12
clflush size : 64

[root@tc2 ~]#

Notice the change in cpu Mhz and bogomips. More than 50% reduction in performance before turning the cpuspeed service off.
If I turn the service back on the performance figures don't reduce again but if I reboot with chkconfig on for cpuspeed it reverts back to the poor performace you can see in the first cpuinfo reading.
I did a test by monitoring my folding@home process before and after and the drop in performance and subsequent increase after turning off the service was very real and significant.
I could post the changes in cpuinfo for the before and afters on the other machines but this should be sufficient
Has anybody else noticed this problem

chkconfig --level 345 cpuspeed off has now been applied to all the fedora7 machines in my household.

FriedChips
1st August 2007, 03:49 PM
yeah I noticed that too, I just booted into the bios and disabled Cool 'n Quiet.

Hlingler
1st August 2007, 03:49 PM
Hello:

??? I'm sorry, I don't see the problem: cpuspeed is intended to control the speed stepping of CPUs that have stepping. If you've configured cpuspeed like I have - with on-demand governor - then the CPU speed will drop to a lower speed step when load is low/higher speed not required.

Regards,V