>Running your program here I see even worse values than that on 2.6.11-mm4 >and it's also interresting to see that for a lot of continuous runs the >values reported drop steadily and eventually settle around ~1100, but if I >insert a sleep 1 between runs, then I see a steady ~1000 reported. >This is all with HZ = 1000
That may be related to the new mix of USER_HZ. I can't really tell, just observed that there is such. >Linux nanosleep() used to have a busywait loop for sleeps less than two >milliseconds. 2.4.x still does. Yes, I know. Linus threw it out during 2.5 because it was deemed to buggy. That did not affect me, because that busywaiting is only possible in !SCHED_OTHER, which I cannot use, because tiny delays are needed in a user-runnable userspace app, and I don't want it suid and stuff. (I've developed an "overhead correction" for accurate(*) realtime replay of logfiles. (*) with respect to the total runtime. Works well.) >You can spin on the gettimeofday() result in userspace. How can I use it? / What does it help me? I just have the gettimeofday() in the example script to measure the total time of nanosleep(). Sometimes, nanosleep completes in the same tick, sometimes (95%), another task is scheduled before returning. I am calling nanosleep repetedly to find out the _average_ time for a 0us-nanosleep(), usually 100/1000 us. Jan Engelhardt -- - 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/
