2.6.0->2.6.1 /proc/cpuinfo behavior change

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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
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