On Mon, 23 Aug 2010, Agustin Ferrin Pozuelo wrote: > Hello, > > I am fine tuning the configuration for an ARM system derived from > AT91SAM9263-EK. > > My goal is to minimize latency, and I am using "cyclictest" from rt-tools > v0.78 for measuring it. > > I get consistently better latency with PREEMPT_DESKTOP over what I get with > PREEMPT_RT. This is an example for a very simple test run, which reflects the > overall results I am getting: > > ### PREEMPT-RT, HRT, no NO_HZ, no RTC, no USE_SLOW_CLOCK > > root@at91sam9263cpc:~# time cyclictest -i 700000 -r -p 80 -l 33 > Clock resolution: 0.000000001 (s.ns) > policy: fifo: loadavg: 0.11 0.10 0.04 1/49 884 > > T: 0 ( 861) P:80 I:700000 C: 33 Min: 370 Act: 627 Avg: 437 Max: > 627 > real 0m 23.51s > user 0m 0.38s > sys 0m 2.20s > > ### PREEMPT-DESKTOP (no RT), HRT, no NO_HZ, no USE_SLOW_CLOCK > root@at91sam9263cpc:~# time cyclictest -i 700000 -r -p 80 -l 33 > Clock resolution: 0.000000001 (s.ns) > policy: fifo: loadavg: 0.24 0.08 0.03 1/46 600 > > T: 0 ( 574) P:80 I:700000 C: 33 Min: 173 Act: 196 Avg: 222 Max: > 378 > real 0m 23.66s > user 0m 0.32s > sys 0m 1.29s 33 loops are not really giving you any useful information. Also run both tests with some background load and not on a fully idle system. Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
