On Tue, Jan 06, 2009 at 09:57:20PM +0100, Peter Zijlstra wrote: > On Tue, 2009-01-06 at 12:34 -0800, Luck, Tony wrote: > > > > All ia64 systems are potentially affected ... but perhaps you might > > > > never see the problem on most because the itc clocks are synced as close > > > > as s/w can get them when cpus are brought on line. > > > > > > Do you want Dimitri to resubmit with this set for all IA64 or leave it > > > as is? > > > > I'd like to understand the impact of turning on HAVE_UNSTABLE_SCHED_CLOCK > > > > It looks like both the i386_defconfig and x86_64_defconfig choose this, > > so at least ia64 will be hitting the well tested code paths > > > > Have the other architectures just not hit this yet? Or do they all have > > "stable" sched_clock() functions? > > > > > > sched_clock() seemed like such a straightforward thing to begin with. A > > quick & easy way to measure a time delta ON THE SAME CPU. I'm not at > > all sure why it has been co-opted for general time measurement. > > It came from the complication of needing to tell a remote cpu's time due > to remote wakeups in the scheduler. But doesn't scheduler tick advance the rq->clock? Why do the others need to fiddle with a remote runqueue's clock? When that cpu starts taking ticks again, it will update it's rq->clock field and start the processes. I guess I am a lot underinformed about the new scheduler design. Robin -- To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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