We need a MONOTONIC clock. Looks like CLOCK_MONOTONIC_FAST appears to be the best choice for us, since we don't care about high precision (10 msec precision is good enough).
Thanks for the benchmarks. Regards -steve On Tue, 2009-07-21 at 11:42 -0700, Sean Chittenden wrote: > re: clock_gettime(2). I have a few random things to add there that > came out of some benchmarking that I did about a year ago for FreeBSD > and is of some relevance. Issues regarding the correctness of yet- > another-clock_id aside, on FreeBSD CLOCK_REALTIME_FAST is ridiculously > fast compared to CLOCK_REALTIME. I don't know what degree of > precision you're looking for in these time calls since > CLOCK_REALTIME_FAST only gets updated once a HZ, but it's a pretty > significant speedup. > > The URL to the full post is below, but the specific excerpts from the > benchmark can be seen here: > > % ./bench_time 9079882 | sort -rnk1 > Timing micro-benchmark. 9079882 syscall iterations. > Avg. us/call Elapsed Name > 9.322484 84.647053 gettimeofday(2) > 8.955324 81.313291 time(3) > 8.648315 78.525684 clock_gettime(2/CLOCK_REALTIME) > 8.598495 78.073325 clock_gettime(2/CLOCK_MONOTONIC) > 0.674194 6.121600 clock_gettime(2/CLOCK_PROF) > 0.648083 5.884515 clock_gettime(2/CLOCK_VIRTUAL) > 0.330556 3.001412 clock_gettime(2/CLOCK_REALTIME_FAST) > 0.306514 2.783111 clock_gettime(2/CLOCK_SECOND) > 0.262788 2.386085 clock_gettime(2/CLOCK_MONOTONIC_FAST) > Last value from gettimeofday(2): 1212380080.620649 > Last value from time(3): 1212380161 > Last value from clock_gettime(2/CLOCK_VIRTUAL): 2.296430000 > Last value from clock_gettime(2/CLOCK_SECOND): 1212380338.000000000 > Last value from clock_gettime(2/CLOCK_REALTIME_FAST): > 1212380243.461081040 > Last value from clock_gettime(2/CLOCK_REALTIME): 1212380240.459788612 > Last value from clock_gettime(2/CLOCK_PROF): 185.560343000 > Last value from clock_gettime(2/CLOCK_MONOTONIC_FAST): 5747219.271879584 > Last value from clock_gettime(2/CLOCK_MONOTONIC): 5747216.886509281 > > http://sean.chittenden.org/news/2008/06/01/ > > Random drive-by $0.02. -sc > > > -- > Sean Chittenden > [email protected] > > > > > > > -- > Sean Chittenden > [email protected] > > > > _______________________________________________ > Openais mailing list > [email protected] > https://lists.linux-foundation.org/mailman/listinfo/openais _______________________________________________ Openais mailing list [email protected] https://lists.linux-foundation.org/mailman/listinfo/openais
