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The behavior of /proc/cpuinfo on cpu frequency scaling has changed
between 2.6.0 and 2.6.1(-mm2). On 2.6.0, /proc/cpuinfo reports the cpu
MHz as set by scaling_setspeed, with bogo-mips numbers along traditional
values.
On 2.6.1-mm2, /proc/cpuinfo _always_ reports cpu MHz == cpuinfo_max_freq, with
bogo-mips values closer to the setting of scaling_setspeed.
In both cases, /proc/stat information appears appropriate to the actual
speed. (At least, AFAICT, that's where gKrellm get's it's info and it seems
to report correctly.)
I didn't glean anything from the changelogs that explains this behavior. Is
it a bug or a feature?
Example output:
########################### 2.6.0 ######################
bash-2.05b# uname -r
2.6.0-ze4400-3
bash-2.05b# echo 1800000 >/sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed
bash-2.05b# cat /proc/cpuinfo
processor : 0
vendor_id : AuthenticAMD
cpu family : 6
model : 8
model name : mobile AMD Athlon(tm) XP2200+
stepping : 1
cpu MHz : 1788.655
cache size : 256 KB
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 sep mtrr pge mca cmov pat pse36 mmx fxsr sse syscall mp mmxext 3dnowext 3dnow
bogomips : 3538.94
bash-2.05b# echo 532000 >/sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed
bash-2.05b# cat /proc/cpuinfo
processor : 0
vendor_id : AuthenticAMD
cpu family : 6
model : 8
model name : mobile AMD Athlon(tm) XP2200+
stepping : 1
cpu MHz : 529.971
cache size : 256 KB
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 sep mtrr pge mca cmov pat pse36 mmx fxsr sse syscall mp mmxext 3dnowext 3dnow
bogomips : 1048.57
########################### 2.6.1-mm2 ######################
bash-2.05b# uname -r
2.6.1-mm2-ze4400-1
bash-2.05b# echo 1800000 >/sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed
bash-2.05b# cat /proc/cpuinfo
processor : 0
vendor_id : AuthenticAMD
cpu family : 6
model : 8
model name : mobile AMD Athlon(tm) XP2200+
stepping : 1
cpu MHz : 1789.000
cache size : 256 KB
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 sep mtrr pge mca cmov pat pse36 mmx fxsr sse syscall mp mmxext 3dnowext 3dnow
bogomips : 1777.66
bash-2.05b# echo 532000 >/sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed
bash-2.05b# cat /proc/cpuinfo
processor : 0
vendor_id : AuthenticAMD
cpu family : 6
model : 8
model name : mobile AMD Athlon(tm) XP2200+
stepping : 1
cpu MHz : 1789.000
cache size : 256 KB
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 sep mtrr pge mca cmov pat pse36 mmx fxsr sse syscall mp mmxext 3dnowext 3dnow
bogomips : 526.71
--
Mark W. Alexander
[email protected]