Re: Measuring cpu time using getrusage
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/
Re: Measuring cpu time using getrusage
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/
Measuring cpu time using getrusage
Hello, 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 anyone know a better way to measure the used cpu cycles of a given process (or part of a program) or can anyone give me a hint if i missed some important fact. Any help appreciated. Thank you in advance. Johann Schuster - 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/
Measuring cpu time using getrusage
Hello, 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 anyone know a better way to measure the used cpu cycles of a given process (or part of a program) or can anyone give me a hint if i missed some important fact. Any help appreciated. Thank you in advance. Johann Schuster - 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/
