Messages in this thread | | | Date | Mon, 5 Sep 2005 13:19:28 +0530 | From | Srivatsa Vaddagiri <> | Subject | Re: [PATCH 1/3] dynticks - implement no idle hz for x86 |
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On Mon, Sep 05, 2005 at 08:37:28AM +0100, Russell King wrote: > That's because, like x86, we've been ignoring each other. ARM > doesn't handle dyntick SMP yet - ARM is fairly young as far as > SMP issues goes, and as yet doesn't include a full SMP > implementation in mainline.
> > Despite that, the timers as implemented on the hardware are not > suitable for dyntick use - attempting to use them, you lose long > term precision of the timer interrupts.
Thats one of the problems I am seeing on x86 as well. Recovering wall-time precisely after sleep is tough esepcially if the interrupt source (PIT) and backing-time source (TSC/PM Timer/HPET) can drift wrt each other. PPC64 should be much better I hope (which is what I intend to take up next).
> > 5. Don't see how DYN_TICK_SKIPPING is being used. In SMP scenario, > > it doesnt make sense since it will have to be per-cpu. The bitmap > > that I talked of exactly tells that (whether a CPU is skipping > > ticks or not). > > What's DYN_TICK_SKIPPING and what's it used for? It looks like > a redundant definition left over from Tony's original implementation.
Tony was using it to signal that all CPUs are idle and timer are being skipped. With the SMP changes I made, I felt it can be substituted with the nohz_cpu_mask bitmap and hence I removed it.
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Thanks and Regards, Srivatsa Vaddagiri, Linux Technology Center, IBM Software Labs, Bangalore, INDIA - 560017 - 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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