Date: Tue, 11 Jan 2005 10:40:58 +0100 From: Ulrich Spoerlein <q@uni.de> To: freebsd-questions@freebsd.org Subject: How to reliably measure user time (getrusage(2)) Message-ID: <20050111094057.GA813@galgenberg.net>
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Hi all, I need to measure the time spent in user mode for rather short-lived processes. Sadly the results vary highly % while true;do \time -p woptsa tsplib/pla7397/pla7397.tsp 2>&1|sed -n /user/p;done user 1.13 user 0.67 user 0.65 user 0.65 user 0.64 user 0.65 % while true;do \time -p woptsa tsplib/pla7397/pla7397.tsp 2>&1|sed -n /user/p;sleep 1;done user 1.22 user 0.87 user 0.75 user 0.67 user 0.86 user 0.74 % while true;do \time -p woptsa tsplib/pla7397/pla7397.tsp 2>&1|sed -n /user/p;sleep 3;done user 1.24 user 1.23 user 1.27 user 1.27 user 1.10 user 1.19 I fail to see how sleeping or waiting between consecutive runs could affect user time. Everything from page faults to I/O is handled inside the kernel, so it shouldn't affect user-time, no? The only library function not taking constant time I could think of would be malloc(3), is that a possibility? Inside the program I'm using getrusage(2) to measure the time my program is executing. kern.hz is set to 1000, this is on a 5-STABLE 1.5GHz Pentium-M. What to do? Ulrich Spoerlein -- PGP Key ID: F0DB9F44 Encrypted mail welcome! Fingerprint: F1CE D062 0CA9 ADE3 349B 2FE8 980A C6B5 F0DB 9F44 Ok, which part of "Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn." didn't you understand?home | help
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