Hello eas-dev, I wanted to give you all an update on EAS product codeline development for Android.

As you may have noticed, the Android Common Kernel branch android-4.4 (https://android.googlesource.com/kernel/common.git/+/android-4.4) now has the EAS product codeline merged. All the patches in there have been validated on a big.LITTLE device. Some of the more experimental patches which were part of the EASr1.2 stack did not make the cut yet, but we will continue to develop them.

All development for the Android Common Kernel will be done in the open so that interested people can see the code, pull the patches and participate in code reviews on the AOSP Gerrit. Development is expected to be continuous - we plan a number of enhancements and upstream backports over the coming months. The main focus for EAS development on the product codeline is to have a kernel which has good performance and efficiency on big.LITTLE devices running Android. As part of this we aim to reduce the delta to mainline as much as possible while of course maintaining any differences necessary for mobile devices.

EAS is intended to be an upstream technology eventually and as we upstream various components we will be backporting them to the product codeline where suitable.

We intend not only to push patches which we consider ready (for code review) but also more ‘experimental’ patches for things that we are working on, an example is here:

https://android-review.googlesource.com/#/c/411501/

This is a stack consisting of 11 patches. The first 6 patches make some changes to the performance index filtering in schedtune, and have a topic of 'fix_performance_index'. On top of those are 2 patches with a topic of 'small_optimizations' which are some optimizations which can be done to existing code. Finally there are 3 patches with a topic of 'experimental_utilest' which is a backport of the current mainline-focussed util_est solution.

Util_est is a filtered version of the existing PELT signals intended to address some of the generally acknowledged responsiveness issues PELT has when compared to WALT. There are multiple mainline ideas about making PELT more suitable for the uses we have, util_est is not the only one and may not be attractive to maintainers but it is included here to help evaluating the signal characteristics.

Where we have multiple patches which make sense to review together, we will send them as a single set and set the topics as appropriate. The review patch stacks will be structured as less controversial changes at the start, and more experimental/risky patches at the end - it's perfectly possible that some will be merged and not others.

As we push patches for review, we intend to post here announcing them.

Since we will now be doing continuous development in the open, the EAS releases (EASr1.3 etc.) become documentation points where we describe the features which are merged and are expected to be merged soon. The development model for android is to have frequent merges of the common kernel, and we feel this fits.

For EAS product codeline testing, we are starting to use Hikey960 as it has big.LITTLE (4xA73+4xA53). Note that we find it essential to add a heatsink and a fan, so firmware thermal capping doesn’t affect EAS performance. We’ve been using a 14mm x 14mm heatsink on the SoC:

http://uk.farnell.com/abl-heatsinks/bga-std-015/heat-sink-bga-standard-26-5-...

with a 5v fan blowing on it. We are using Baylibre ACME for power measurement, which is supported in LISA (https://github.com/ARM-software/lisa) which we're using for development testing and trace analysis.

The current (21-June-2017) Hikey960 status is that cpufreq/cpuidle is working using the ARM Trusted Firmware. There is an open issue relating to OPP switch time on the little cluster which is being investigated. We are also engaged with Leo in validating the energy model.

For Android Common Kernel 4.9 (https://android.googlesource.com/kernel/common.git/+/android-4.9) we have a first pass of a patch stack bringing it up to parity with android-4.4 which is being tested on Juno and original hikey. This will be posted for review against the android-4.9 branch and is a change to the existing EAS code that’s there. The tests are passing on Juno, but please note there is significantly less testing than for kernel 4.4

We very much welcome broad participation in the future direction of EAS for products - to participate in EAS product codeline development, please ensure you are registered for a googlesource Gerrit userid which you can get at https://android.googlesource.com/new-password

Thanks,

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