Hi Darren,

On 01/02/17 16:37, Darren Greene wrote:

Hello all,

I have an x86 based platform which is running android. I wanted to play around with the EAS patches to see if it would improve power numbers on it.

This sounds very interesting!

I had a few basic questions regarding this:

1. Can EAS be used with x86 based platforms ? I see some arm/arm64

energy model related patches in the eas integration tree (git://linux-arm.org/linux-power.git). However, there aren't any x86 specific changes present. Is that because no x86 specific changes are required or just that it is untested there ?

EAS is designed to work on heterogeneous dual-cluster systems but we also support a dual-cluster ARM64 SMP platform (Hikey) in our integration repo. So EAS currently operates in MC and DIE sched_domain level. It attempts to do a better job of packing vs spreading tasks based on PM related energy model data.

SMT is currently not supported though.

A list of x86 specific changes:

Create an energy model for your processor similar to the ARM64 example and provide it to the task scheduler via struct sched_domain_topology_level x86_topology[].

Create a frequency invariant engine (based on X86_FEATURE_APERFMPERF ?) and wire it up to the task scheduler.

Set the EAS sched_domain flag SD_SHARE_CAP_STATES indicating which cores are sharing a DVFS domain.

Depending on the actual cpu topology and PM subsystem design there might be more to do.

2. Is it expected that EAS would show significant power savings on SMP

systems or just on HMP systems ?

We expect to see power savings even on SMP platforms due to better control over packing vs spreading of tasks.

3. Would there be any cpufreq/cpuidle integration be required for x86

specifically ? If so, would I need to base them on the arm stuff or is there any other reference code.

You would need to use cpufreq driver with target_index() callback (e.g. acpi-cpufreq), so not the current Intel P-State driver. Turbo Boost is not supported, you would have to disable it.

4. Are there other in-flight patches that need to be applied over the

patches in the eas integration tree for best results ?

Besides the EAS integration tree we have the EAS product integration which has additional features. Chris' email '[Eas-dev] EAS 1.2 Pre-alpha Experimental Branch now available for Pixel/Pixel XL' he sent out yesterday on eas-dev has more on this.

If indeed the EAS patches can be used on x86. then I would be interested in integrating and providing results on my platform. Please guide.

Let us know if we can support you further on this.

Cheers,

-- Dietmar

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