Messages in this thread | | | Date | Mon, 14 Jul 2008 11:30:00 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [PATCH, RFC] use hrtimer in sched_clock |
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On Fri, 11 Jul 2008, Uwe Kleine-König wrote: > This should make it unnecessary to overwrite sched_clock for a higher > precision. > With this patch I get sub-jiffie timing with CONFIG_PRINTK_TIME=y. > > Signed-off-by: Uwe Kleine-König <Uwe.Kleine-Koenig@digi.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Ingo Molnar <mingo@elte.hu> > --- > Hello, > > I tested the patch on arch-arm/mach-ns9xxx and it seem seams to work. > But I admit I didn't test it deeply and I didn't measure if there is any > overhead.
There is lots of overhead and your approach is simply wrong.
> unsigned long long __attribute__((weak)) sched_clock(void)
The correct way to solve it is to override sched_clock() with a high resolution implementation for your hardware platform. sched_clock is a weak function to provide a default implementation based on jiffies.
If you do a grep -r sched_clock arch/arm you'll find a couple of examples how to override sched_clock().
Thanks,
tglx | |