[parisc-linux] sched_clock implementation

Matthew Wilcox willy@debian.org
Thu, 18 Sep 2003 21:35:10 +0100


Anyone want to do better than the lame implementation?  ;-)

----- Forwarded message from Andrew Morton <akpm@osdl.org> -----

I'll be merging Ingo & Con's CPOU scheduler changes into Linus's tree soon.

It does require that the architecture provides a new timing function:

A lame implementation is:

/*
 * Returns nanoseconds
 */

unsigned long long sched_clock(void)
{
	return (unsigned long long)jiffies * (1000000000 / HZ);
}

But for best CPU scheduler results the architecture should try to return a
higher-resolution number than this of course.

sched_clock() has no absolute time requirements: it just has to return some
number which goes up by 1,000,000,000 times per second.

I already have implementations for x86, ppc, sparc64 and ia64.

I have a completely stupid ppc64 implementation which is only accurate on
1GHz CPUs.  Anton please note!

As for the rest, it'll break the build, sorry.

----- End forwarded message -----

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