Optimizing Your Android Applications

Transcription

1 Optimizing Your Android Applications Alexander Nelson November 27th, 2017 University of Arkansas - Department of Computer Science and Computer Engineering

2 The Problem

3 Reminder Immediacy and responsiveness Three time limits 1 : < 0.1s - User feels system acts instantaneously < 1s - Maintain user s flow of thought < 10s - Maintain user s attention Plan for these limits! Use loading screens/timers when necessary 1 Jacob Nielsen

4 Why do you need to optimize? Reasons to optimize: 1) Meet time constraints 2) Users complain about apps that run slowly = bad reviews! 3) Inefficient background services use battery

5 Why is optimizing difficult? Optimizing mobile applications is difficult because: Mobile phones have less compute resources than workstations Different mobile devices with various specifications UI- or Event-driven code is harder to profile Running on the emulator doesn t necessarily match the performance on the device Especially if the device has a JIT

6 Optimizing Android Applications

7 What are goals for optimization? The primary goals for optimization are: Meet all time constraints Use less battery Use less cellular data We already went over this

8 Optimizing for Performance Primary focus of this lecture is optimizing for performance Resources:

9 First Principle Most important design decision? Algorithm and data structure selection No performance tip can outrun a bad design decision

10 Writing Efficient Code Two basic rules for writing efficient code: Don t do work that you don t need to do Don t allocate memory if you can avoid it

11 Avoid creating unnecessary objects Creating an object = Memory allocation Creating a lot of objects forces garbage collection Tips for reducing object creation: Change method signatures to manipulate existing objects Slice multi-dimensional arrays into parallel one-dimension arrays Avoid creating short-term temporary objects whenever possible

12 Prefer Static If you don t need to alter an object s fields make method static Invocations will be 15-20% faster Good coding practice anyway method signature indicates the object can t be manipulated Use Static Final for constants Only applies to primitives and String constants Reduces initialization and access time

13 Use Enhanced For Loop Syntax The enhanced for loop (or for-each loop) can be used for Iterable collections and arrays Zero is slowest One is slower than Two without a JIT Equivalent with a JIT

14 Package Access for Private Inner Classes Accesses to private values/methods from inside private inner classes occur thorough static accessor methods Performance overhead to use accessor methods Use package level instead of private when not sensitive

15 Avoid using Floating Point Rule of Thumb: Floating point is 2x slower than integer on android devices In terms of speed, float and double are equivalent Double is 2x larger in memory If space isn t an issue and you require float, use double over float Along those lines Avoid divide if possible Many devices lack a hardware divider

16 Know and Use Libraries Library code is likely safer and more optimized than hand-written code The system can replace library calls with hand-coded assembler Using System.arraycopy() is 9x faster on a Nexus One with JIT than a hand-coded copy loop

17 Native Methods Using the Java Native Interface may or may not produce performance gain Will require compilation on each architecture the code will run on Often, the JIT will optimize code equal-to or better than hand-written code For more on the JNI with Android: perf-jni.html

18 Performance Myths Invoking methods with an exact typed variable is more efficient Slightly true for devices without a JIT Caching field accesses is faster About 20% faster without JIT About the same with a JIT

19 Measure your performance Before starting to micro-optimize, make sure you have a problem to solve Accurately measure existing performance and the goal Traceview can be useful for profiling BUT Traceview currently disables existing JITs, and may misattribute time

20 Measuring Performance

21 Tools to measure performance Tools: Traceview Hierarchy View Memory Monitor (deprecated) Method Tracer (deprecated) Android Profiler (Android Stuido 3.0)

22 Traceview Traceview Provides graphical representation of trace logs Traces generated by instrumenting code with the Debug class

23 Generating Trace Files Debug.startMethodTracing() + Debug.stopMethodTracing() Logs trace data form start->stop Requires external write permission startmethodtracing(filename) can be used to create named tracefiles Log files are by default stored in getexternalfilesdir()

24 Hierarchy View Use to locate an examine view elements within current application

25 Android Profiler Android Profiler New to Android Studio 3.0 Replaces functionality of previous monitoring tools

26 Advanced Profiling If running API 25 or lower, you need to enable advanced profiling Enables: The event timeline on all profiler windows The number of allocated objects in Memory Profiler Garbage collection events in Memory Profiler Details about all transmitted files in Network Profiler Advanced profiling does slow speed (especially involving JIT)

27 Enabling Advanced Profiling How to enable Advanced Profiling: 1. Run>Edit Configurations 2. Select app module in left pane 3. Click Profiling Tab 4. Check Enable Advanced Profiling

28 CPU Profiler CPU Profiler Monitor Application CPU usage at macro level (For detail, record method traces)

29 CPU Profiler 1. Event Timeline UI Events 2. CPU Timeline Real time CPU Usage 3. Thread Activity Timeline Each thread and activity 4. Recording Configurations Sampled/Instrumented 5. Record Button Starts/stops recording a method trace

30 Memory Profiler Memory Profiler Identify memory leaks and churn Shows real-time graph of application memory use Can capture a heap-dump, force garbage collection, track memory allocation

31 Memory Profiler 1. Force Garbage Collect 2. Capture Heap Dump 3. Record Memory Allocation 4. Zoom in/out of timeline 6. Jump forward to live memory data 7. Event Timeline 8. Memory Use Timeline

32 Network Profiler Network Profiler Display and inspect realtime network activity Examine how/when app transfers data in order to optimize

33 Network Profiler Network Profiler

34 Inspecting GPU Rendering To achieve 60 frame per second, GPU should be drawing approx. every 16ms You can view GPU rendering graph on the device Settings >Developer Options >Monitoring >Profile GPU Rendering Select On Screen as Bars Open App you want to profile

35 Inspect GPU Rendering

36 Inspect Battery Usage Battery Historian Docker image which uses device logs of battery usage