avgtime - Small D util for your everyday benchmarking needs

[Marco Leise]

Am Fri, 23 Mar 2012 09:02:01 +0100
schrieb "Juan Manuel Cabo" <juanmanuel.cabo at gmail.com>:

> On Friday, 23 March 2012 at 05:16:20 UTC, Andrei Alexandrescu 
> wrote:
> [.....]
> >> (man, the gaussian curve is everywhere, it never ceases to
> >> perplex me).
> >
> > I'm actually surprised. I'm working on benchmarking lately and 
> > the distributions I get are very concentrated around the 
> > minimum.
> >
> > Andrei
> 
> 
> Well, the shape of the curve depends a lot on
> how the random noise gets inside the measurement.
> 
> I like  'ls -lR'  because the randomness comes
> from everywhere, and its quite bell shaped.
> I guess there is a lot of I/O mess (even if
> I/O is all cached, there are lots of opportunities
> for kernel mutexes to mess everything I guess).
> 
> When testing "/bin/sleep 0.5", it will be quite
> a pretty boring histogram.
> 
> And I guess than when testing something thats only
> CPU bound and doesn't make too much syscalls,
> the shape is more concentrated in a few values.
> 
> 
> On the other hand, I'm getting some weird bimodal
> (two peaks) curves sometimes, like the one I put on
> the README.md.
> It's definitely because of my laptop's CPU throttling,
> because it went away when I disabled it (for the curious
> ones, in ubuntu 64bit, here is a way to disable
> throttling (WARNING: might get hot until you undo or reboot):
> 
> echo 1600000 > 
> /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq
> 
> echo 1600000 > 
> /sys/devices/system/cpu/cpu1/cpufreq/scaling_min_freq
> 
> (yes my cpu is 1.6GHz, but it rocks).
> 
> 
> --jm

On Gnome I use the cpufreq-applet to change the the frequency governor from 'ondemand' to 'performance'. That's better than manually setting a minimum frequency. (Alternatively you can set it through the /sys interface.) - Unless this governor is not compiled into the kernel.

-- 
Marco