Memory Management in Titanium AppsTIM POULSENSOFTWARE ENGINEER, TOOLING TEAM

@skypanther

What are our goals?

No crashesFast, responsive appsDo moreLonger battery lifeHappy users!

<0.1 second = “instant”<1 second = “uninterrupted”~10 seconds = user loses attention -- Nielsen Norman Group

Topics I’ll cover

Memory limitsWhat uses memoryGarbage collectionGarbage is goodAlloy specificsProfiling

http://muppet.wikia.com/wiki/I_Love_Trash

Memory limits

Pre-ICS ~16-24 MBNexus 4 ~96 MB“Large heap” enabled ~128 MB+

iPhone 4 ~50 MBiPhone 5/5s ~100 MBiPad2 ~50 MBiPad Air ~100 MB

(Limit ~10% of device RAM)

What’s in a Titanium app?

Your app’s code

Titanium APIs

Kroll bridge

Native components & libraries

• Your app’s code• Alloy’s libraries• Graphics• Custom fonts• Data – queries,

network calls, etc.

Garbage Collection

Garbage Collection

Memory Management Masterclass, Addy Osmani https://www.youtube.com/watch?v=LaxbdIyBkL0

Garbage

Garbage Collection

Obj 1 Obj 2 Obj 4Obj

3Live

Reserve

Memory Management Masterclass, Addy Osmani https://www.youtube.com/watch?v=LaxbdIyBkL0

Obj 5

GC Pause

JavaScript Mark & Sweep

Obj 1 Obj 2 Obj 4Ob

j 3Live

Reserve

Memory Management Masterclass, Addy Osmani https://www.youtube.com/watch?v=LaxbdIyBkL0

Obj 5

JavaScript & native objects

Your app’s code

Titanium APIs

Kroll bridge

Native components & libraries

Object

Object

Native memory cleanup

Android / Java layer GC:Runs at its own intervalSlower & less frequent

iOSManual allocation/de-allocation by core SDKARC supported in modules

Garbage Collection Takeaways

Every allocation gets you closer to a GC pauseMore objects = more time for GCGC is automaticJavaScript and native processes to consider

http://muppet.wikia.com/wiki/I_Love_Trash

Efficient and garbage-friendly

Efficient and GC friendly

Watch those imagesAvoid global variablesDon’t create variables you don’t need toClean up after yourselfA couple of extras...

Images

Decompressed in memoryFile format doesn’t matter!Pixels and color depth doUse scaled resolutionsLazy load themRemove them when you canDon’t use them

200 by 200 px image= 40,000 pixels x 32 bits per pixel= 1,280,000 bits= 160,000 Bytes= 156.25 KB= ~1/6th MB

A 1536 x 2048 image ~ 12 MB

“Why not just use xhdpi images across all resolutions and let the device scale to the right size?” -- Q&A user

“I’ve got a table with 200 rows, each with an image and my app crashes. Titanium sucks” -- Q&A user

Custom fonts

Don’t use global variables

Scope - global & functionGlobals are bad:

Can’t be garbage collectedCollisions (unintended value changes)

Watch for accidental globalsUse scope to your advantage:

Wrap in functions / IIFEs

Locals & Globals

CommonJS Singleton

Don’t create variables you don’t need to

Don’t create variables you don’t need to

Closures

Unintended references

Clean up

Set to null or undefinedLet JavaScript clean up for youAvoid tight loops

IIFEs (self-calling functions)

Too tight

Process data in the right place

Data Data

SQLite

Android specifics

Use the R bitmapsStop servicesClean up in onPause() or onuserleavehint eventEspecially sensitive to rapid allocation/de-allocation

Alloy considerations

Alloy considerations

Use the frameworkModel/Collection referencesJust don’t – er, clean-up functionsRemember the basics

Use the framework

config.json Alloy.CFG.fooAlloy.Globals -> delete Alloy.Globals.fooCompiler / platform directives

(OS_IOS, OS_ANDROID, etc.)

But don’t abuse it

Don’t put images or large objects into Alloy.GlobalsDon’t declare variables in alloy.jsController listeners: $.view.on() and $.view.off()

Model/Collection listeners: coll.on() and coll.off()

Model/Collection cleanup

Speaking of, just don’t...

Well, at least do a good job...

Remember the basics: don’t create variables unnecessarily

Remember the basics: clean up after yourself

Remember the basics: even if you have to get tricky

Profiling and testing

github.com/skypanther/LeakyApp

Instruments

Instruments

Monitor

Monitor, almost useful...

Takeaways

Limit images, lazy load, use fonts ...I love trash (aka: code with GC in mind)

Let Alloy do its stuffBut clean up after yourself

Profile your apps

Thank YouTIM POULSEN@skypanther