Red Hat Bugzilla – Bug 249972
cpuspeed-1.2.1-2.fc7 defaults to lowest value in cpu frequency
Last modified: 2007-11-30 17:12:11 EST
Description of problem: Notice the CPU speed is reported as 1GHz in /proc/cpuinfo -> processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 14 model name : Genuine Intel(R) CPU T2400 @ 1.83GHz stepping : 8 cpu MHz : 1000.000 cache size : 2048 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 : 10 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx constant_tsc pni monitor vmx est tm2 xtpr bogomips : 3664.18 clflush size : 64 On the contrary, "dmesg" shows these boot messages -> CPU 0 irqstacks, hard=c0790000 soft=c0770000 PID hash table entries: 4096 (order: 12, 16384 bytes) Detected 1830.942 MHz processor. Which frequency value is correct? BTW, my laptop is connected to the power outlet so it should run on maximum speed (by default). Version-Release number of selected component (if applicable): kernel-2.6.22.1-33.fc7 How reproducible: Always
$ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors ondemand userspace performance $ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor ondemand $ cat /sys/devices/system/cpu/cpu1/cpufreq/scaling_available_frequencies 1833000 1333000 1000000 It seems by default (as per /etc/sysconfig/cpuspeed) the governor is set to ondemand which causes the speed to be the lowest (1000MHz). I had to many set the GOVERNOR field to "performance" in /etc/sysconfig/cpuspeed and restart the service to get the maximum speed of 1833MHz. I would assume that when the laptop is running on AC power, the speed should not default to the mininum.
Nope, ondemand quickly ramps up to max speed when its needed -- i.e. On Demand, thus the name of the governor. :) More background: The idea here is to save power. The same driver runs on lots of desktop systems, which are always on AC power. Can't do much good if it just sits there full-throttle all the time. So you either want to switch to the performance governor when on AC, or just use ondemand as its intended -- it does ramp the speed up when its actually needed.