On Mon, Jan 21, 2013 at 07:06:59PM -0600, Matt Sealey wrote: > On Mon, Jan 21, 2013 at 6:51 PM, John Stultz <john.stu...@linaro.org> wrote: > > On 01/21/2013 02:54 PM, Matt Sealey wrote: > >> > >> On Mon, Jan 21, 2013 at 4:36 PM, John Stultz <john.stu...@linaro.org> > >> wrote: > >>> > >>> On 01/21/2013 01:14 PM, Matt Sealey wrote: > > > > As far as jiffies rating, from jiffies.c: > > .rating = 1, /* lowest valid rating*/ > > > > So I'm not sure what you mean by "the debug on the kernel log is telling me > > it has a higher resolution". > > Oh, it is just if I actually don't run setup_sched_clock on my > platform, it gives a little message (with #define DEBUG 1 in > sched_clock.c)
sched_clock() has nothing to do with time keeping, and that HZ/NO_HZ/HRTIMERS don't affect it (when it isn't being derived from jiffies). Now, sched_clock() is there to give the scheduler a _fast_ to access, higher resolution clock than is available from other sources, so that there's ways of accurately measuring the amount of time processes run for, and other such measurements - and it uses that to determine how to schedule a particular task and when to preempt it. Not providing it means you get those measurements at HZ-based resolution, which is suboptimal for tasks which run often for sub-HZ periods (which can end up accumulating zero run time.) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/