On Wed, 14 Feb 2007, Johann Schuster wrote: > currently i'm trying to measure the cpu times for > numerical algorithms written in C using two calls of > getrusage() and then calculating the time difference. > > According to the man page of getrusage i looked at the > user time of my process. Surprisingly the measured user > times vary strongly depending on the system load of the > machine. > A heavy system load nearly doubles the measured time > for my routine.
Does your system have hyperthreading? (look at whether the siblings field in /proc/cpuinfo is greater than one) If yes, there is no way to accurately measure runtimes because the (single-threaded) performance of your CPU depends on the other tasks running. Just disable hyperthreading for these measurements. Tim - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/