Merge "Add initial README file for TARE."

apex/jobscheduler/service/java/com/android/server/tare/README.md

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+Welcome to The Android Resource Economy (TARE for short). If you're reading this, you may be
+wondering what all of this code is for and what it means. TARE is an attempt to apply economic
+principles to resource (principally battery) management. It acknowledges that battery is a limited
+resource on mobile devices and that the system must allocate and apportion those resources
+accordingly. Every action (running a job, firing an alarm, using the network, using the CPU,
+etc.) has a cost. Once that action has been performed and that bit of battery has been drained, it's
+no longer available for someone else (another app) to use until the user charges the device again.
+
+The key tenets of TARE are:
+
+1. Charge for actions --- when an app performs an action, reduce its access to resources in the
+   future. This should help remind everyone that everything they do has a cost.
+1. Reward for good actions --- reward and encourage behavior that provides value to the user
+1. Fine bad actions --- fine and discourage behavior that is bad for the user
+
+# Details
+
+To achieve the goal laid out by TARE, we introduce the concept of Android Resource Credits
+(ARCs for short).
+
+## How do ARCs work?
+
+ARCs are required to perform any action while in the background. Some actions may have a fixed cost.
+Others may be more dynamic (some may even allow apps to bid higher ARCs for some actions to have
+them prioritized). If the app doesn't have enough ARCs, the action can't be performed. Apps are
+granted ARCs (below a certain threshold) as the device charges. Apps are also granted ARCs for
+providing user value (eg. for doing things that engage the user).
+
+ARCs will be used across the entire system as one unified concept. When an app performs an action,
+it pulls from the same account, regardless of the action. This means that apps can choose to do more
+of one action in lieu of being able to do as much of another. For example, an app can choose to use
+all of its ARCs for jobs if it doesn't want to schedule any alarms.
+
+### Scaling
+
+With the ARC system, we can limit the total number of ARCs in circulation, thus limiting how much
+total work can be done, regardless of how many apps the user has installed.
+
+# Definitions
+
+* ARC: Android Resource Credits are the "currency" units used as an abstraction layer over the real
+  battery drain. They allow the system to standardize costs and prices across various devices.
+* NARC: The smallest unit of an ARC. A narc is 1 nano-ARC.
+* Satiated: used to refer to when the device is fully charged (at 100% battery level)