Daniel Stutzbach, 07.07.2011 18:55:

On Thu, Jul 7, 2011 at 7:56 AM, Antonio Cuni wrote:

...

This is using the "ondemand" governor, which is the default on my system. I tried to run it also with "performance", which in theory should give better performance and smaller stdev, but in practice it does not (I don't know why, honestly)

For what it's worth, I ran some similar experiments last year and found that "performance" yielded much lower standard deviations for certain performance tests, compared to "on demand". I no longer recall which ones unfortunately, but in a nutshell "on demand" is just as good only when it's smart enough detect that it should be using the maximum CPU frequency.

Sometimes it doesn't, and the standard deviation goes up a few orders of magnitude.

That matches my benchmarking experience as well.

Stefan