Messages in this thread | | | Subject | Re: update on hrtimer based select/poll and range-hrtimers | From | Peter Zijlstra <> | Date | Sun, 07 Sep 2008 22:46:39 +0200 |
| |
On Sun, 2008-09-07 at 11:11 -0700, Arjan van de Ven wrote: > Hi, > > since the last lkml posting I've merged a few fixes and added comments > from Peter, and I've redone the "estimate_accuracy" function. > > Rather than reposting the entire series, I'll point to the git tree at > > git://git.kernel.org/pub/scm/linux/kernel/git/arjan/linux-2.6-hrtimer.git > > and I've pasted the new function below. > Rather than having the hardcoded steps from the "Linus" function, I've > turned it into: > 0 for realtime tasks > "0.1% of the time" for not-nice, not realtime tasks > "0.5% of the time" for nice, not realtime tasks > with a cap of 100msec for both. > > I would like to request feedback on this approach; I think this is > better than the "hardcoded steps" as before, but maybe someone can come > up with an ever better idea....
logarithms pop to mind (again :-)
> static unsigned long __estimate_accuracy(struct timespec *tv) > { > unsigned long slack; > int divfactor = 1000; > > if (task_nice(current))
This triggers for both -nice and +nice tasks, it might be worth differentiating between those.
> divfactor = divfactor / 5; > > slack = tv->tv_nsec / divfactor; > slack += tv->tv_sec * (NSEC_PER_SEC/divfactor); > > if (slack > 100 * NSEC_PER_MSEC) > slack = 100 * NSEC_PER_MSEC; > return slack; > } > > static unsigned long estimate_accuracy(struct timespec *tv) > { > unsigned long ret; > struct timespec now; > > /* > * Realtime tasks get a slack of 0 for obvious reasons. > */ > > if (current->policy == SCHED_FIFO || > current->policy == SCHED_RR) > return 0;
rt_task(current) ?
> ktime_get_ts(&now); > now = timespec_sub(*tv, now); > ret = __estimate_accuracy(&now); > if (ret < current->timer_slack_ns) > return current->timer_slack_ns;
pull out the max from __estimate_accuracy() and use clamp() here?
> return ret; > }
| |