Messages in this thread | | | Date | Wed, 25 Jan 2012 15:04:18 +0100 | From | Daniel Lezcano <> | Subject | Re: [PATCH 0/3] coupled cpuidle state support |
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On 01/20/2012 09:40 PM, Colin Cross wrote: > On Fri, Jan 20, 2012 at 12:46 AM, Daniel Lezcano > <daniel.lezcano@linaro.org> wrote: >> Hi Colin, >> >> this patchset could be interesting to resolve in a generic way the cpu >> dependencies. >> What is the status of this patchset ? > I can't do much with it right now, because I don't have any devices > that can do SMP idle with a v3.2 kernel. I've started working on an > updated version that avoids the spinlock, but it might be a while > before I can test and post it. I'm mostly looking for feedback on the > approach taken in this patch, and whether it will be useful for other > SoCs besides Tegra and OMAP4.
Hi Colin,
I will be happy to test your patchset. Do you have a pointer to a more recent kernel ?
>> Did you have the opportunity to measure the power consumption with and >> without this patchset ? > Power consumption will be very dependent on the specific SoC in > question. The most important factors are the power savings of the > independent cpuidle state (normally WFI) vs. the hotplug state > (normally 1 cpu in OFF), and the workload being tested. > > On a very idle system, these patches result in the same total power as > hotplugging one cpu and letting the other idle normally. On a 25% > busy system, you might see a slight increase in power, as the best > independent cpuidle state might be WFI, vs 1 cpu in OFF mode in > hotplug. On OMAP4, that difference is small, on the order of 10 mW. > Once you hit the threshold where a hotplug governor would have > hotplugged in the second cpu (lets say 40%), the savings from these > patches are enormous, as you can hit the lowest power state up to 60% > of the time, where the hotplug solution would never be going below WFI > on both cpus. On OMAP4, that can be well over 100 mW.
Interesting.
Thanks
-- Daniel
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