Messages in this thread | | | Date | Fri, 25 Aug 2006 09:58:05 +0200 | From | Arjan van de Ven <> | Subject | Re: [RFC] maximum latency tracking infrastructure |
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Nick Piggin wrote: > Arjan van de Ven wrote: >> Jesse Barnes wrote: >> >>> On Thursday, August 24, 2006 10:41 am, Arjan van de Ven wrote: >>> >>>> The reason for adding this infrastructure is that power management in >>>> the idle loop needs to make a tradeoff between latency and power >>>> savings (deeper power save modes have a longer latency to running code >>>> again). >>> >>> >>> What if a processor was already in a sleep state when a call to >>> set_acceptable_latency() latency occurs? >> >> >> there's nothing sane that can be done in that case; any wake up >> already will cause the unwanted latency! >> A premature wakeup is only making it happen *now*, but now is as >> inconvenient a time as any... >> (in fact it may be a worst case time scenario, say, an audio >> interrupt...) > > Surely you would call set_acceptable_latency() *before* running such > operation that requires the given latency? And that set_acceptable_latency > would block the caller until all CPUs are set to wake within this latency. > > That would be the API semantics I would expect, anyway.
but that means it blocks, and thus can't be used in irq context
(the usage model I imagine happens most is a set_acceptable_latency() which can block during device init, with either no or a very course limit, and a modify_acceptable_latency(), which cannot block, from irq context or device open) - 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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