Performance #5 cpu and battery

Idan Felix10/08/2016

http://bit.ly/2aMrRzgWifi password : dotheimpossible

CPU & BatteryMost eclectic we had so far

5

First,

Idan Felix

I’m 33 years old

VaronisAndroid Academy TLV

Idan Felix

I’m 33 years old

VaronisAndroid Academy TLV

Yonatan LevinGoogle Developer

Expert & Android @ Gett

Idan FelixSenior Android &

Redhead Varonis

Jonathan Yarkoni

Android Developer & Advocate Ironsource

Android Academy Staff

Britt Barak

Android LeadReal

Muiriel Felix

Android Design

I am selling out

Logistics

Logistics

Yossi SegevAndroid

@Crave

https://www.facebook.com/groups/android.academy.ils/

What’s next?14/9 - Britt- Threading

30 / 10 / 2016New course coming

30 / 10 / 2016New course coming

30 / 10 / 2016New course coming

30 / 10 / 2016New course coming

● +: Networking Debt.● A: CPU

○ Theory○ Practice

● B: Battery○ Theory○ Practice

10/08/2016

CPU & Battery

- Assess the problem and establish acceptable behavior.

- Measure perf b4 modification.

- Identify bottleneck.- Remove bottleneck.- Measure perf after

modification.- If better, adopt.

If worse, put it back.

Methods of Systematic performance improvement

https://en.wikipedia.org/wiki/Performance_tuning

Bonus Part: Networking

+“A man in debt is so far a slave.”Ralph Waldo Emerson

Last month, Yonatan talked about

- Networks basics- Retrofit 2.0- Caching, Prefetching- Bundling-up with Android (~ Sync Adapters),

Or at least playing nice (~ Job Scheduler)- Doze (Will be revised

today)Really, check it out. https://docs.google.com/presentation/d/1maecLjfOOy38_VJWc2YKzoXGSR2ulF3KLG6wmoJ3OwE/edit?usp=sharing

Serialization

How objects move across domains*

Serialization/Deserialization

Serialization

Deserialization

JSON Class Representation

{ "starwars": { "number_of_episodes": 1, "realDarthVaderName": "Anakin Skywalker", "nextEpisodeRelease": "01-12-2016 01:00:00+3:00GMT" }}

Sounds like a good idea, right?

Serialization/Deserialization

Advantage - It’s human readable. And it’s its weakest point too.

GZipabilityMemory overhead

GZip

When communicating with servers, it makes sense to compress the data, and it’s quite easy to do so. GZip is a GNU-Licensed compression algorithm, which is a merge of 2 compression algorithms: Lampel-Ziv-77 and Huffman-Codes,That works in 32kb chunks.

GZip - LZ77 Concept - Back References

למעלה מלמטה המתגלגל גלגל קול

ומתגלגלות הולכות סתומות מרכבות

Credit for the example: Orevi Joe

2,28,4

7,27,210,2 49,4 41,2

5,2

How to mess up compressibility

When you’re sending arrays or lists of large objects, the JSON format OOB has a lot of redundancy, and if the object is large, then some of the references fail.

How to mess up compressibility - Solution

Consider crafting a DTO that would be optimized for smaller footprint and compression.Have numbers and similar strings close to each other.Consider refactoring a list-of-object to an object-of-lists.

JSON Class Representation[ { "id": 314, "shoe_size": 42, "show_image": "-- 32kB Base64 representation of a PNG --", }, { "id": 42, "shoe_size": 42, "show_image": "-- 32kB Base64 representation of another PNG --", }, { "id": 456, "shoe_size": 42, "show_image": "-- 32kB Base64 representation of a different PNG --", },}

JSON Class Representation{ "id": [314,42,456], "shoe_sizes": [42,42,42], "show_images": [ "-- 32kB Base64 representation of a PNG --", "-- 32kB Base64 representation of another PNG --", "-- 32kB Base64 representation of a different PNG --" ]}

Json vs. Optimized-JSonHumanReadability

Performance

JSonOptimiz

edJSon

Flat Buffers

- Faster- Lighter

FlatBuffers

Colt McAnlis: https://youtu.be/IwxIIUypnTE

How it works?

Process

1.Create schema2.Compile schema with flatc compiler3.Import generated files into your project4.Read from byte[]:

java.nio.ByteBuffer buf = builder.dataBuffer();// Deserialize the data from the buffer.StarWars starWars = StarWars.getRootAsStarWars(buf);

Any Questions?

Any Questions?

● +: Networking Debt.● A: CPU

○ Theory○ Practice

● B: Battery○ Theory○ Practice

10/08/2016

CPU & Battery

Part A: CPUA

“Tears come from the heart and not from the brain. ”

Leonardo Di Vinci

Understanding CPU- How does my phone know Java?- Big-O Notation and an intro to Data Structures- Auto-Boxing- Optimized Data Structures (Sparse Arrays and

Maps)- Things we can’t control

But before we begin, something totally unrelated..

What is

Eyjafjörður?

I wonder…How does my phone know

Java?

Well, IT DOESN’T

Build → ExecuteOn your PC, Gradle does a really complicatedBuild process, that takes the Java Code andTurns it into an APK.We’ll go into what it does, So we can appreciate the beauty.

Build → ExecuteSimplified Walkthrough the build:A. Manifest Merging

B. AAPT goes over the RES file and produces R.java and resources

C. Javac takes the code and produces a JAR file

D. ProGuard optimizes the JAR(s)

E.Dx takes the JAR(s) and produces a DEX file

F. AAPT takes everything (+ the Manifest), signs it and packs it to an APK

G. JarSigner signs the APK

Read more: https://developer.android.com/studio/build/index.html

The APK is unzipped on the device. The customized Java Runtime loads and executes your code.

Build → Execute

If KitKat (4.4) and below

DALVIKIf Lollipop and above

ART

Remember this classic diagram?

Build → Execute

We are here.

Build → Execute: Dalvik

Dalvik is a VM that..:- uses dex (and odex) files to run programs.

Thanks, DEX, for using a short to index the method table. #65K

- Instead of being Stack based (Like the JVM), it is Register based.

- It’s main idea:

Being optimized for low memory consumption.

Build → Execute: Dalvik

And then there was Froyo (2.2)Google added an amazing ability, called JIT compiling (by trace).

JIT - Compile parts (~by trace) of the “ByteCode” to Machine-Code.Performance was better - but the optimization options were limited.

Runtime-Perf: What to measure?

These are some of the KPIs for the Runtime:- Performance - App Startup Time- Jank- Battery Footprint- Memory Footprint

Build → Execute: Art

The Art (~Android Runtime) uses the same dx format,

But instead of JIT-Compiling, uses AOT-Compiling.

When installing an app, the phone compiles the entire dex to machine-code, and binds (statically link) whatever it needs to the framework.

Build → Execute: Art

In N, ART does both JIT and AOT.It profiles your code, and decides which methods it should compile.Since compilation is not a trivial task, it does it only when the device is 100% charged and connected to the charger.Read: In Nougat, connecting your phone to a charger makes it work faster.

So, Is your phone a computer or not?

Why Yes:It has a CPU, Memory, GPU, an OS, It runs Java

Why No:Not the same VM, Not the same amounts of CPU, Memory, Not the same usage patterns and expectations.

If it was a computer...

Big-O and Data Structures

This is what we were taught in Intro2CS, DataStructures, and etc.:

- Considering very large inputs (limn->∞) and ignore constants

- The Big O Notation: “1.02n” >> “n3 + 5n2” === “30n3” > “1000n2”

- Counting operations- Accessing a memory cell by address is O(1)

Loops on some input are O(n),

- Trade-off Everything

Big-O and Data Structures

Big-O and Data Structures

Some rules still apply in mobile:- Use the right algorithm, - Use the right data-structure,- Be Smart

Don’t forget that this is a mobile device.

Storing a list of numbers

You need to store n integers.If you know what n is, use an array.If you don’t - What do you do?(Support insert-last and get operation)

Possible Solution:

Create an array-like interface:int get(int index)void insertLast(int value)

Guess or get an initial size, and if needed, Create a new array with more room, copy the items, and use the new array.

Discuss.

Possible Solution, Now with Generics:

Create an array-like interface:T get(int index)void insert(T value, int index)

This is also called an ArrayList<T>.

Are there any implications? Discuss.

How Generics Work

In Java, The compiler translates your <T>s to Objects, and adds casting as necessary.So, you can’t use int (or boolean, or double, or long, …), so instead, you use Integer (or Boolean, Double, or Long), which do the same thing, more or less.

Now, consider these codes

int i = 5; Integer i = 5;int j = i + 2;Integer j = i + 2;

What do these compile to?

Now, consider these codes

int i = 5; Integer i = 5;int j = i + 2;Integer j = i + 2;public void noBoxing(); Code: 0: iconst_5 1: istore_1 2: iload_1 3: iconst_2 4: iadd 5: istore_2 6: return

Proof: javap -c Boxing.java

public void withBoxing(); Code: 0: iconst_5 1: invokestatic #2 // Method java/lang/Integer.valueOf:(I)Ljava/lang/Integer; 4: astore_1 5: aload_1 6: invokevirtual #3 // Method java/lang/Integer.intValue:()I 9: iconst_2 10: iadd 11: invokestatic #2 // Method java/lang/Integer.valueOf:(I)Ljava/lang/Integer; 14: astore_2 15: return

Now, consider this code

ArrayList<Integer> list = new ArrayList<Integer>();

list.add(1);list.add(2);

Same issue.

Now, consider this code

ArrayList<Integer> list = new ArrayList<Integer>();For (int i = 0; i++; i < list.size()){

int value = list.get(i);} Same

issue.

AutoBoxing

To handle previous code samples, The runtime automagically takes your int, puts it inside a box, called Integer and stores it in the heap.

This is AutoBoxing.

Colt McAnlis: https://youtu.be/dgzOwuoXVJU

AVOID BOXING

BEWARE of AUTO-BOXINGColt McAnlis: https://youtu.be/dgzOwuoXVJU

Any Questions?

Storing a list of objects, by Key

You need to store n objects, by key.If you know what n is, use an array.If you don’t - What do you do?(Support an insert and get operations)

Storing a list of objects, by Key

Consider this API:void insert(key, value)int get(key)

What’s in a key?

Consider this task:You have a list of devices that you want to retrieve by their IMEI.Here’s a sample IMEI: 53865487920334156 (17 digits)It doesn’t make sense to have an array with 1017 cells…

Same for Creditcards, ID numbers, GUIDs, and mostly anything that has an id and there’s a lot of it in the world, and you will not need them all

Here’s what we’ll do- Squash the key to something we can handle

(~HashCode),Store according to the key

- Handle Conflicts somehow (Open-hash / Closed-hash)

- Handle resizing somehow

- If we add Generics, This will be called java.util.HashMap<TKey, TValue>

Is it the right algorithm?

- Inserting: Amortized O(1), but up to O(n)- Searching: Amortized O(1), but up to O(n)

- Memory Consumption - Not so good.

What’s wrong with it?

- If you’re using Integers or Longs (IMEIs), for keys or for values, you might hit AutoBoxing.

- The “Entry” class (internal implementation detail) is another layer of abstraction that gets allocated that we don’t need.

- Compacting and Expending are expensive

HashMap solution 1: ArrayMaps

ArrayMaps (from android.util) use a different algorithm:It uses 2 arrays - one for the values and the keys, and one for the hashes, which is kept sorted.

Colt McAnlis: https://youtu.be/ORgucLTtTDI

HashMap solution 1: ArrayMaps

ArrayMaps (from android.util) use a different algorithm:It uses 2 arrays - one for the values and the keys, and one for the hashes, which is kept sorted.Insertion - O(n)Searching - O(log n)

Colt McAnlis: https://youtu.be/ORgucLTtTDI

HashMap solution 1: ArrayMaps

ArrayMaps (from android.util) use a different algorithm:It uses 2 arrays - one for the values and the keys, and one for the hashes, which is kept sorted.Insertion - O(n)Searching - O(log n)

Memory consumption - much better, but autoboxing is still an issueColt McAnlis: https://youtu.be/ORgucLTtTDI

HashMap Solution #1: ArrayMaps

This data-structure is useful on mobile for 2 use-cases:

HashMap solution 2: SparseArrays and co.

Sparse Arrays are optimized for no-autoboxing, and use similar algorithms for storage as ArrayMaps.Use SparseArrays when the keys or the values are primitives (partial):

Colt McAnlis: https://youtu.be/I16lz26WyzQ

Key Type Value Type SparseArray

Integer Object SparseArray

Integer Boolean SparseBooleanArray

Long Object LongSparseArray

Important for job interviews

SparseArrays and Array-Maps:GET - Requires binary search - O(log

n)INS - Require binary search and

moving - O(n)(and they also don’t retain order, נבלות)

Another “what does this compiles to”

Consider the following code:// from Iterators.foo();ArrayList<Foo> foos = new ArrayList<Foo>();for (Foo foo : foos){ // … Do something with foo}

public void foo(); Code: 0: new #2 // class java/util/ArrayList 3: dup 4: invokespecial #3 // Method java/util/ArrayList."<init>":()V 7: astore_1 8: aload_1 9: invokevirtual #4 // Method java/util/ArrayList.iterator:()Ljava/util/Iterator; 12: astore_2 13: aload_2 14: invokeinterface #5, 1 // InterfaceMethod java/util/Iterator.hasNext:()Z 19: ifeq 35 22: aload_2 23: invokeinterface #6, 1 // InterfaceMethod java/util/Iterator.next:()Ljava/lang/Object; 28: checkcast #7 // class Foo 31: astore_3 32: goto 13 35: return

What does it compile to? (In Bytecode)

Now, Let’s compare public void baz(){ ArrayList<Foo> foos = new ArrayList<Foo>(); int size = foos.size(); for (int i = 0; i < size; i++){ Foo foo = foos.get(i); // Do something with foo... } }

Now, Let’s compare public void baz(); Code: 0: new #2 // class java/util/ArrayList 3: dup 4: invokespecial #3 // Method java/util/ArrayList."<init>":()V 7: astore_1 8: aload_1 9: invokevirtual #8 // Method java/util/ArrayList.size:()I 12: istore_2 13: iconst_0 14: istore_3 15: iload_3 16: iload_2 17: if_icmpge 36 20: aload_1 21: iload_3 22: invokevirtual #9 // Method java/util/ArrayList.get:(I)Ljava/lang/Object; 25: checkcast #7 // class Foo 28: astore 4 30: iinc 3, 1 33: goto 15 36: return

Hmm. Android vs. Java?- Java: use for(int i : list) because that’s how

we do it in java.

- Android: do what Java says, especially if you’re using

an iterator. https://developer.android.com/training/articles/perf-tips.html#Loops

- Colt McAnlis:Use a CS101 for loop, avoid the iterator if

possible.See for yourself: https://youtu.be/MZOf3pOAM6A

One thing we can’t control

Android can change the speed of the CPU to conserve battery.

Slower CPU ⇒ Battery lasts longer

This might cause 2 symptoms:- Dropped frames (it takes 20ms for the CPU to speed-up

again)- Normal things take longer

This is OK

Colt McAnlis: https://youtu.be/c8u3fEM3JG0

Any Questions?

Any Questions?

● +: Networking Debt.● A: CPU

○ Theory○ Practice

● B: Battery○ Theory○ Practice

10/08/2016

CPU & Battery

A recent study showed that 100% of your users don’t use your app when their battery is

out of juice.

The BatteryB

Understanding Battery- Battery theory

- As A Developer, How to reduce battery usage

- As ANDROID, How to reduce battery usage

Measurement Units

Ampere (A) is a unit of electric current. It describes how much power something needs at an instant.Milli-Ampere (mA) is the unit that we actually use, because it’s a mobile device, and things don’t use a lot of power.Example: My GPS needs 140mA, and my 4G chip needs 180mA.https://en.wikipedia.org/wiki/Ampere

Measurement Units

However, it doesn’t take time into considerations - That’s why we use mAh.

Example: Nexus 5X battery is 2,700 mAh

https://en.wikipedia.org/wiki/Ampere-hour

Battery Theory

My GPS needs 140mA, and my 4G chip needs 180mA.

Which is better for getting a location:

using the GPS or the 4G chip?

Battery Theory

My GPS needs 140mA, and my 4G chip needs 180mA.

Getting a GPS lock takes about 25 seconds, so:25s x 140mA ~= 1mAh

Battery Theory

My GPS needs 140mA, and my 4G chip needs 180mA.

Getting network location lock takes about 2 seconds, so:2s x 180mA ~= 0.1mAhJeffrey Sharkey: https://youtu.be/OUemfrKe65c (From Google I/O 2009)

So, What’s killing your battery?

The Scree

n

The Mode

mThe GPS

Foreground work Background work

About the screen

So what can you do?

Taste of what’s possible: https://developer.android.com/reference/android/app/job/JobInfo.Builder.html

Reduce

Keep background activity to minimum

DeferWait with the activity until the device is

charging

CoalesceTry to piggy-back, batch,

queue or group background work

with other background

tasks that has to be done

The battery and the Radio

True or false:

3G and WIFI need (more or less)

the same amount of power~180 mAh

The battery and the Radio

However, downloading 100mb via 3G radio takes 1’56’’ and via WIFI 0’10’’

180mAh x 10sec = 0.5 mAh180mAh x 116sec = 5.8 mAh

The battery and the Radio

Also: - Radio wake-up costs a lot of power- Radio has to stay awake for responses (and responses of

responses)

- Radio goes to sleep after about ~20sec of activity.

Dive Deeper: Ran Nachmani @ Big Android BBQ 2015: https://youtu.be/LO_Swql0zVg

The battery and the Radio

So what can you do?

I/O 2016: https://youtu.be/VC2Hlb22mZM

Guide: https://developer.android.com/training/efficient-downloads/efficient-network-access.html

Reduce Defer Coalesce

- If it’s not important - Don’t- Reduce payload (GZIP,

FlatBuffers)

- Use the JobScheduler to wait for

- Charger- WIFI

- Piggy-back with SyncAdapters

- Prefetch and Batch

Change usage pattern according to network state!

Tool: DDMS / ADM

The Android Device Monitor can really help in understanding what the network is doing.

Any Questions?

GPS in action

Your device can find its locations using 3 devices:- The GPS, which uses few satellites for exact

location.- The 3G network that uses cell-tower triangulation.- Some WIFI networks can also hint of where you

are.Each of these is a location provider.

Most use the Fused Location Provider from Google Play services.It merges all location providers for bests results and optimal footprint.protected void createLocationRequest() { LocationRequest mLocationRequest = new LocationRequest(); mLocationRequest.setInterval(10000); mLocationRequest.setFastestInterval(5000); mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);}

GPS in action

https://developer.android.com/training/location/change-location-settings.html

GPS in action

True or false:

You might be updated on location

More frequent than you ask.

The battery and the GPS

We already talked about using the GPS vs the 3G data.What else can we do?

More: Colt McAnlis: https://youtu.be/81W61JA6YHw

Reduce Defer Coalesce

- Ask for less accurate location

- Ask for less updates- Limit number of callbacks

- Ask for less updates - Piggy-back other GPS requests

Reduce the location battery footprint of your app.

Set the priority for the accuracy you need.PRIORITY_LOW_POWER (~10km "city" accuracy)PRIORITY_BALANCED_POWER_ACCURACY (~100m "block" accuracy)PRIORITY_HIGH_ACCURACY (accurate as possible at the expense of battery life)

The battery and the GPS

https://developers.google.com/android/reference/com/google/android/gms/location/LocationRequest

Reduce

- Ask for less accurate location

- Ask for less updates- Limit number of callbacks

The battery and the GPS

Reduce the location battery footprint of your app.

Set the interval as high as you can. mLocationRequest.setInterval(10000);

https://developers.google.com/android/reference/com/google/android/gms/location/LocationRequest

DeferReduc

e- Ask for less accurate

location- Ask for less updates- Limit number of callbacks

The battery and the GPS

Reduce the location battery footprint of your app.

Also limit the number of callbacks. mLocationRequest.setFastestInterval(5000);

https://developers.google.com/android/reference/com/google/android/gms/location/LocationRequest

Reduce

- Ask for less accurate location

- Ask for less updates- Limit number of callbacks

The battery and the GPS

Reduce the location battery footprint of your app.

Use PRIORITY_NO_POWER to passively listen for location updates from other clients.

https://developers.google.com/android/reference/com/google/android/gms/location/LocationRequest

- Piggy-back other GPS requests

Coalesce

Any Questions?

So, What’s killing your battery?

The Scree

n

The Mode

mThe GPS

Foreground work Background work

About the screen

THIS WAS A LIE

Wasting screen / cpu energy

Sometimes, you want to keep the device awake to do some work.Perhaps you want the screen to stay on while watching a video, or wake-up from sleep to calculate something periodically.

This can be done with WakeLocks:PowerManager powerManager = (PowerManager) getSystemService(POWER_SERVICE);WakeLock wakeLock = powerManager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "MyWakelockTag");wakeLock.acquire();Training: https://developer.android.com/training/scheduling/wakelock.html Colt McAnlis: https://youtu.be/reMau7d0yeg

Wasting screen / cpu energy

However, it’s really important to handle WakeLocks with care.

- Beware of dependencies (User data, server faults, etc.)

- Always use a timeout

Training: https://developer.android.com/training/scheduling/wakelock.html Colt McAnlis: https://youtu.be/reMau7d0yeg

Short story

Friday, ~8:00AMMy phone has ~22%

Mr. Levin: “Put it on the floor in your bag, don’t touch it,

and let it go into DOZE.”

OK.

What does Android do to reserve battery?

Doze

Introduced with Marshmallow (6.0, API 23),

https://developer.android.com/training/monitoring-device-state/doze-standby.html

Doze

When the device is in this state:- Network access is suspended- The device ignores wake locks- Alarms (a la AlarmManager) don’t get execute (unless

While-Idle or setAlarmClock)

- No SyncAdapters or JobSchedulers

- System also does not do Wifi Scanshttps://developer.android.com/training/monitoring-device-state/doze-standby.html

So we listened to you for 2 hours for nothing?

Don’t be mad Don’t do anything

If you have a problem with Doze, It means that you have a problem with a simple fact:

Your users have lifeThey might forget their tablet at home when they leave for a 3 days trip to Amsterdam, and would love for it to have battery when they come back from their trip. #TrueStory #FML

Doze

Joanna Smith, Big Android BBQ 2015: https://youtu.be/Rwshwq_vI1s

Doze

Besides that,

Don’t do anything.If you’re using all the stuff we taught, you should be good- SyncAdapters, JobSchedulers will work as expected.

- Alarms are to be watched, and other network access too.Joanna Smith, Big Android BBQ 2015: https://youtu.be/Rwshwq_vI1s

Doze

These are the states that the phone can be in:

Joanna Smith, Big Android BBQ 2015: https://youtu.be/Rwshwq_vI1s

Active Inactive Idle Pending Idle

Idle Maintenan

ceThis transition takes ~2h

Remember my story? About a 45m lecture?

Doze

In Android Nougat, The terms for entering Doze were loosened.This means that even while the device is in the user’spocket it can go into Doze. Still same principle apply:

Don’t do anything about it.

Any Questions?

Felix stop!!! :)

To Amsterdam...

You leave us...

Missing from this lecture

Missing from this lecture

https://youtu.be/dZL2LDAg5cs

Any Questions?

Idan Felix10/08/2016

CPU & BatteryMost eclectic we had so far

5

Idan Felix10/08/2016

Everything is Trade-off

Be as smart as you can be. 5

Idan Felix10/08/2016

Drive Home Safely.5