I usuall optimize my code for clean *code* and don't spend much time
worrying about optimizing for particular hardware, or really worrying
about hardware at all.  This is why I was surprised when I ran this on
our deparment computer lab:

    wking@xphy1:~$ grep MHz /proc/cpuinfo
    cpu MHz         : 2000.000
    cpu MHz         : 3166.000

What!  Why is the CPU speed changing for a dual-core chip?  Some
searching around lead me to [cpufrequtils][] (Debian: `cpufrequtils`,
Gentoo: `sys-power/cpufrequtils`) and `cpufreq-info`:

    wking@xphy1$ cpufreq-info 
    cpufrequtils 006: cpufreq-info (C) Dominik Brodowski 2004-2009
    Report errors and bugs to cpufreq@vger.kernel.org, please.
    analyzing CPU 0:
      driver: acpi-cpufreq
      CPUs which run at the same hardware frequency: 0
      CPUs which need to have their frequency coordinated by software: 0
      maximum transition latency: 10.0 us.
      hardware limits: 2.00 GHz - 3.17 GHz
      available frequency steps: 3.17 GHz, 2.67 GHz, 2.33 GHz, 2.00 GHz
      available cpufreq governors: conservative, ondemand, userspace,
                      powersave, performance
      current policy: frequency should be within 2.00 GHz and 3.17 GHz.
                      The governor "ondemand" may decide which speed to use
                      within this range.
      current CPU frequency is 2.00 GHz (asserted by call to hardware).
      cpufreq stats: 3.17 GHz:4.40%, 2.67 GHz:0.05%, 2.33 GHz:0.05%,
                      2.00 GHz:95.49%  (3538)
    analyzing CPU 1:
      driver: acpi-cpufreq
      CPUs which run at the same hardware frequency: 1
      CPUs which need to have their frequency coordinated by software: 1
      maximum transition latency: 10.0 us.
      hardware limits: 2.00 GHz - 3.17 GHz
      available frequency steps: 3.17 GHz, 2.67 GHz, 2.33 GHz, 2.00 GHz
      available cpufreq governors: conservative, ondemand, userspace,
                      powersave, performance
      current policy: frequency should be within 2.00 GHz and 3.17 GHz.
                      The governor "ondemand" may decide which speed to use
                      within this range.
      current CPU frequency is 2.00 GHz (asserted by call to hardware).
      cpufreq stats: 3.17 GHz:4.03%, 2.67 GHz:0.77%, 2.33 GHz:0.03%,
                      2.00 GHz:95.17%  (3743)

Now it makes sense ;).  Apparently the current (possibly throttled)
frequency is listed in `/proc/cpuinfo`, not the maximum frequency.

Also, the computer lab computers don't seem to be working very hard ;).

[cpufrequtils]: http://www.kernel.org/pub/linux/utils/kernel/cpufreq/cpufrequtils.html

[[!tag tags/linux]]
[[!tag tags/programming]]