Stephen Wille Padnos wrote: > > I have done reasonably extensive testing on an Intel Core 2 Duo CPU, and > I found that the latencies weren't improved much simply by using an > isolated CPU. What did help (a lot!) was making the Linux-managed core > do a lot of nothing. Running the bash script `while true ; do echo > "nothing" > /dev/null ; done` improved matters a lot. Some additional > trimming of loaded modules, combined with using ext2 instead of ext3 > (kjournald made a blip every 5 seconds) made that machine get 200-400ns > average latencies, with the highest spikes still in the 2 us range. >
It didn't occur to me at the time, but I bet I know why the "do a lot of nothing" task helped. I bet the Linux idle task puts the CPU into a HALT or some other low power state. Even though the RT stuff is running on the other core, there might be some side effects of that state that hurt latency. I could certainly see how it would help on a single core system - if the CPU halts, then the latency will include whatever time is needed to get it out of that halt state, which might be non-trivial. Regards, John Kasunich ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
