On 14/03/10 14:24, Bruno Haible wrote: > Hi Chen, > >> ... it was consistently (as in every run for 20 runs) faster, and thus I've >> included it in the patch. > > Thanks. I'll wait for the FSF notification that the legal papers have arrived.
Hi Chen, The copyright stuff is sorted now I presume? > >> This is not what I expected at all, and I'm having a hard time coming up with >> a reason why this is > > 15 years ago, on a Linux/x86 machine, I could measure CPU performance with > about 1% precision (with 3 or 5 runs of a program). At the same time, on > Windows, I got only about 5% precision. > > On SPARC CPUs, sometimes the same program was 30% slower than the previous > day. > So, such platforms were unusable for benchmarking. lol > Today, x86 CPUs have additional complexity: multiple CPU cores that fight over > the memory bus; hyperthreads. The Linux memory management has become more > complex as well (the kernel actively swapping out some pages). Sometimes > you're > even running inside a virtual machine. I usually can get only about 2% of > precision nowadays. That's why I keep my single core laptop for benchmarking. After a suspend/resume cycle or large memory thrashing performance can vary quite a bit, but for multiple runs within a particular session, it's quite stable. cheers, Pádraig.
