Messages in this thread | | | Date | Mon, 14 Jul 2008 11:48:47 +0200 | From | Uwe Kleine-König <> | Subject | Re: [PATCH, RFC] use hrtimer in sched_clock |
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Hello Thomas,
Thomas Gleixner wrote: > 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. I expected to have some overhead, but can you please elaborate on "simply wrong"? I will try to measure the actual overhead but cannot promise to find time for that in the near future.
> > 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(). I new that and my purpose was to make this unneeded. Would be nice, wouldn't it?
Thanks and best regards, Uwe
-- Uwe Kleine-König, Software Engineer Digi International GmbH Branch Breisach, Küferstrasse 8, 79206 Breisach, Germany Tax: 315/5781/0242 / VAT: DE153662976 / Reg. Amtsgericht Dortmund HRB 13962 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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