How is bogomips computed?

[Yong Huang]

Hi, Chet,

I think the ht flag in /proc/cpuinfo indicates whether I have hyperthreading.
So yes, I have it:

$ grep -w ht /proc/cpuinfo
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov
pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext lm 3dnowext 3dnow pni
cx16
...

On a different server with exactly same OS release and kernel version and also
ht flag in cpuinfo, all CPUs' bogomips are the same:

$ grep bogomips /proc/cpuinfo
bogomips        : 6675.48
bogomips        : 6666.32
bogomips        : 6666.20
bogomips        : 6666.40

However, I think this is very relevant. The server that shows different
bogomips uses AuthenticAMD CPUs while the second server I mentioned uses
GenuineIntel. I checked two other boxes, one AMD one Intel, and found the
"problem" on AMD only.

Katsu, I read the full article you suggested. It doesnt' seem to answer my
question.

I think I can assume AMD CPUs generally run slower with the same CPU rating, if
we test many types of applications and compute an average.

Yong Huang


*********** Chet Nichols III wrote ***********

Do you happen to have hyperthreading enabled?

On Wed, Jul 9, 2008 at 1:23 PM, Yong Huang <yong321 at yahoo.com> wrote:

> Even though bogomips as shown in /proc/cpuinfo is a rough estimation of CPU
> capability, there must be some truth to it. Is it computed by doing a
> simple
> busy loop to see how many iterations it can go through within some set
> time? I
> can't imagine half of the CPUs on one of our boxes have only half the
> bogomips
> of the others:
>
> $ grep bogomips /proc/cpuinfo
> bogomips        : 4018.62
> bogomips        : 2009.31
> bogomips        : 4018.62
> bogomips        : 2009.31
> bogomips        : 4018.62
> bogomips        : 2009.31
> bogomips        : 4018.62
> bogomips        : 2009.31
>
> Yong Huang