Unblocking The Main Thread_ Solving ANRs and Frozen Frames.pdf

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Unblocking The Main Thread:
Solving ANRs and Frozen Frames
Sinan Kozak
Staff Android Developer
Google Developer Expert

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Sinan Kozak
Google Developer Expert &
Staff Android Developer
12 years Android experience
@snnkzk
I wrote a chapter about performance in 2014
book with GDG community Ankara, Turkey.

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We deliver
food over
70 countries
with a single rider application

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Production is wild,
really wild for Android
10s of thousands of diﬀerent devices

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Diﬀerent stages of
Jank
What to measure?

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Rendering a frame
between 16ms and 700ms
Scroll
Animations
Frame rate
Slow Rendering
Rendering a frame
between 700ms and 5s
App startup
Navigation
Frozen Frame
Blocking main thread
over 5 seconds
Not being able to
handle user inputs
Application Not Responding
Diﬀerent stages of Jank

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Apps have limited
resources
Focus on things we can control

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This his how bad rendering looks like

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This is how acceptable render looks like

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Can slow runtime cause app crashes?
YES
● User will continue to click the screen. Either ANR or Crash could
happen for diﬀerent reasons.
● Foreground services crash when their start is delayed more than
5 seconds

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Is there a magic
solution?
Maybe…

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Reuse thread pool
Reducing allocation
Fix memory leaks
Release Memory Pressure
R8/Proguard optimization
Fast dependency Injection
WebP and vector images
Use reportFullyDrawn
Baseline proﬁle
Render First Frame
Execute in background
Reduce recomposition
Measure and optimize
Drain Main Thread
Diﬀerent categories of solutions

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Quick wins
01 Execute in background
RxJava, Coroutine and other thread solutions
02 Thread pool reuse
Utilize thread pools
03 R8/Proguard optimization
Auto apply proven optimizations
04 Reducing allocation
Only store necessary data in memory
05 No memory leak
Fix all leaks
06 Dependency Injection
Time consuming injection should be in background
07 WebP and vector images
Simpler the image faster to draw
08 Less recomposition
Avoid recurring recomposition
09 Correct Compose API
Use lambda based api for fast changing values
10 reportFullyDrawn
Talk to OS about what needs to prioritize
11 Baseline proﬁle
Make sure OS optimize app startup
12 Measure and optimize
We can have optimized apps

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Reducing
allocation
Garbage collector pauses
runtime to clean up
Spare memory for all features
Photo by Andreas Gücklhorn on Unsplash

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Reducing allocation

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In your heap dump, look for memory leaks caused by any of the following:
● Long-lived references to Activity, Context, View, Drawable, and other objects
that might hold a reference to the Activity or Context container.
● Non-static inner classes, such as a Runnable, that can hold an Activity instance.
● Caches that hold objects longer than necessary.
Memory leak
In your heap dump, look for memory leaks caused by any of the
following:
● Long-lived references to Activity, Context, View, Drawable, and
other objects that might hold a reference to the Activity or
Context container.
● Listeners or Runnables can hold an Activity instance.
● Caches that hold objects longer than necessary.

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Running with memory leaks

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Memory leak
Detection:
● Leak Canary
● Android Studio
● Strict Mode
● Third party memory analyzer
Leak Canary Plumber ﬁxes known common issues.
https://github.com/square/leakcanary/tree/main/plumber

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Collect
StrictMode
violations
Easiest way to collect data

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Collect StrictMode violations

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Collect StrictMode violations

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Use multi thread
solutions
● IO operations
● Data parsing
● Encryption
● Any time consuming operation
Move work to the background
Photo by Campbell on Unsplash

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Execute in background with Coroutine
https://kotlinlang.org/docs/coroutines-overview.html
https://developer.android.com/kotlin/coroutines#use-coroutines-for-main-safety

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Share Thread Pools
A single thread can use 1-3 MB memory

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Features with own thread pools
Most of features have their own thread pool
● RxJava
● Coroutine
● OkHttp
● Image loaders
● Room
● RecyclerView + DiﬀUtil
● WorkManager
● … many more
And they have APIs to change thread pool

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Share Thread Pools
We shared Coroutine Dispatchers with
● RxJava
● OkHttp
● Coil
● WorkManager
Thread count reduced 180+ to 130~ during high load operation
“asOkHttpExecutorService” is a custom implementation that only handle execute function

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Runtime optimization
Code we write is not same as core runs on the device

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R8 and proguard are mainly obfuscation tools, but…
They also shrink and optimize codes.
In order to optimize your app even further, R8 inspects your code at a deeper level to
remove more unused code or, where possible, rewrite your code to make it less
verbose. The following are a few examples of such optimizations:
● If your code never takes the else {} branch for a given if/else statement, R8
might remove the code for the else {} branch.
● If your code calls a method in only a few places, R8 might remove the method
and inline it at the few call sites.
Prefer "proguard-android-optimize.txt" over default
Improve app performance by up to 30%
R8/Proguard optimization

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More resources optimizations
High level documentation
https://developer.android.com/build/shrink-code
https://www.guardsquare.com/manual/conﬁguration/optimizations
Detailed posts
https://jakewharton.com/blog/

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Compose recomposition
optimizations
Does count matter?

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Recomposition
Recompose count shouldn’t affect correctness.
The compose runtime might end up recomposing a lot more than
you’d expect.
Just looking at the code does not reveal reasons.
Functions can be inline
Classes can be mutable

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https://dev.to/zachklipp/scoped-recomposition-jetpack-compose-what-happens-when-state-changes-l78
Donut hole skipping
Compose API design enforces
better performance with
lambda and scoping

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Donut hole skipping
● Lambdas are special in Compose
● The runtime keeps track of values used in lambdas
● Lambdas get reevaluated if values change
● Composable can be skipped if they are not aﬀected by change

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Rendering ﬁrst pixel
Avoid heavy operations during start up

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WebP
WebP is an image ﬁle format from Google that provides lossy compression
(like JPEG) as well as transparency (like PNG) but can provide better
compression than either JPEG or PNG
Average %26 less space
More eﬃcient
Android Studio can convert images
https://developer.android.com/studio/write/convert-webp
Resource optimizations

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Vector Drawables
is a vector graphic defined in an XML file as a
set of points, lines, and curves along with its
associated color information.
Scalable
svg can be converted to Vector drawables
Simpler is better
The initial loading of a vector drawable can cost
more CPU cycles than the corresponding raster
image.
Size save should be justified with performance
Use Avocado tool to simplify complex vectors
https://github.com/alexjlockwood/avocado

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Dependency Injection
DI slowness eﬀects ﬁrst frame rendering

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Lost of things run on main thread during dependency injection
● Activity/Fragment creation
● Field assignments
● init blocks of injected classes

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P50 P90
One of the our major improvements is creating OkHttp and
Encrypted SharedPreference in the background thread.

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Delay creation of expensive instances
Create in background thread
If you use Dagger, use dagger.Lazy

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Show me real example
Dependency injection issue
Ineﬃcient vector drawable usage

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Eﬀect of Vector Drawable

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Creation of Vector Images can be consuming

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Eﬀect of Vector Drawable

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Talk to
designers for
simpler svgs
You can use webp images or
image loading libraries

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Load heavy resources in background
Code lab - Practical performance problem solving in Jetpack Compose
https://developer.android.google.cn/codelabs/jetpack-compose-performance

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Play Store helps you
Use reportFullyDrawn for better cloud proﬁles

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Baseline Profiles
● Helps app startup after new install or update
● Android run ahead of time compile to prepare app startup
● We can modify and create aggregated profiles
● Libraries can have their own baseline profiles
● Compose benefit from baseline profiles
https://developer.android.com/topic/performance/baselineprofiles/create-baselineprofile

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How to
measure?
Real data vs proﬁling

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How to measure?
Data from proﬁling
● perfetto.dev
● Systrace
● CPU and memory allocation
● Layout inspector and debugger
Data from users
● Firebase Performance Monitoring or similar solutions
● JankStat library
● Memory leaks
● Strict mode

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Measure as much as you can
● Profile a variant close to release
● Measure high level first
● Add more granular metrics and traces
● Use benchmark tests
● Profile before and after changes
● Collect data from production

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Random ANR points during app start up
ANR stacktrace is delayed
Android 14 has improved ANR capturing
Filter ANR for Android 14+ to get better picture
ANR report only contain last executed things
There could be other slowness on main thread

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Visible performance is
one side of the coin
App needs to be performant in all operations.

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10 years retro of
performance suggestions
Comments are welcome in QA

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10 years retro of performance suggestions
View hierarchy - ViewStub > Composables with if else check
ListView - ViewHolder > RecyclerView + LazyColumn
Memory leaks > Memory leaks still exists
Running in background > Coroutine
We still have things to optimized.
They are just diﬀerent.

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I hope you have this chart in your next release

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Thank you
github.com/kozaxinan linkedin.com/in/sinankozak strava.com/athletes/sinankozak
@snnkzk
Do you have any questions?

Unblocking The Main Thread_ Solving ANRs and Frozen Frames.pdf

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