GC You Later, Allocator

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GC You Later, Allocator github.com/swankjesse/memory

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Let’s Make Breakfast

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Kitchen Counters You allocate space You do stuff in that space You clean it up and start again

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Counter Space is Precious More counter space lets you do more things! When counter space is tight, you thrash

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Locality Items that are used together should be close together

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Let’s Make an App

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RUN!

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9:57 9:57

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9:57 9:57

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Compose UI ANDROID iOS SwiftUI SHARED NearbyGator GatorsService Code

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data class NearbyGator( val name: String, val distance: Double, )

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/** * Detects green toothy gators using Bluetooth GATT ERS. */ interface GatorsService : AutoCloseable { fun addListener(listener: Listener) fun removeListener(listener: Listener) interface Listener { fun onGators(nearbyGators: List) } }

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class NearbyGatorsContent( gatorsService: GatorsService, ) : GatorsService.Listener { var list by mutableStateOf>(listOf()) init { gatorsService.addListener(this) } override fun onGators(nearbyGators: List) { list = nearbyGators } }

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class NearbyGatorsContent: ObservableObject, GatorsServiceListener { @Published var array: [NearbyGator] = [] init(gatorsService: GatorsService) { gatorsService.addListener(listener: self) } func onGators(nearbyGators: [NearbyGator]) { self.array = nearbyGators } }

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@Composable fun Content() { if (showNearbyGators) { NearbyGatorsScreen( content = NearbyGatorsContent(service), onDismiss = { showNearbyGators = false }, ).Show() } ... }

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struct ContentView: View { ... var body: some View { Button( ... ) .sheet(isPresented: $showNearbyGators) { NearbyGatorsView( NearbyGatorsContent(service), $showNearbyGators ) } } }

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Logical Memory

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val chompy = NearbyGator( name = "Chompy", distance = 5.5, ) NearbyGator name "Chompy" distance 5.5

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val chompy = NearbyGator( name = "Chompy", distance = 5.5, ) String data "Chompy" NearbyGator name "Chompy" distance 5.5

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val chompy = NearbyGator( name = "Chompy", distance = 5.5, ) String data "Chompy" NearbyGator name "Chompy" distance 5.5

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val chompy = NearbyGator( name = "Chompy", distance = 5.5, ) CharArray length 6 0 C 1 h 2 o 3 m 4 p 5 y String data "Chompy" NearbyGator name "Chompy" distance 5.5

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val chompy = NearbyGator( name = "Chompy", distance = 5.5, ) CharArray length 6 0 C 1 h 2 o 3 m 4 p 5 y String data "Chompy" NearbyGator name "Chompy" distance 5.5

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val chompy = NearbyGator( name = "Chompy", distance = 5.5, ) CharArray length 6 0 C 1 h 2 o 3 m 4 p 5 y String data "Chompy" class NearbyGator name "Chompy" distance 5.5

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val chompy = NearbyGator( name = "Chompy", distance = 5.5, ) CharArray length 6 0 C 1 h 2 o 3 m 4 p 5 y String data "Chompy" class NearbyGator name "Chompy" distance 5.5 Class name "NearbyGator" superclass Any ...

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val chompy = NearbyGator( name = "Chompy", distance = 5.5, ) CharArray length 6 0 C 1 h 2 o 3 m 4 p 5 y String data "Chompy" class NearbyGator name "Chompy" distance 5.5 class Class name "NearbyGator" superclass Any ... class Class name "Any" superclass null ...

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val chompy = NearbyGator( name = "Chompy", distance = 5.5, ) class CharArray length 6 0 C 1 h 2 o 3 m 4 p 5 y class String data "Chompy" class NearbyGator name "Chompy" distance 5.5 class Class name "NearbyGator" superclass Any ... class Class name "Any" superclass null ... class Class name "Class" superclass Any ...

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val chompy = NearbyGator( name = "Chompy", distance = 5.5, ) CharArray 6 C h o m p y String "Chompy" NearbyGator "Chompy" 5.5 Class "NearbyGator" Any ... Class "Any" null ... Class "Class" Any ...

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val chompy = NearbyGator( name = "Chompy", distance = 5.5, ) 6 C h o m p y 5.5 ... null ... ...

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val chompy = NearbyGator( name = "Chompy", distance = 5.5, ) 0x06 0x43 0x68 0x6f 0x6d 0x70 0x79 0x40160000000000 ... 0x00 ... ...

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Logical Memory is a Big Graph! Each object is just a combination of: • Values like Doubles and Chars • References to other objects Your program works by manipulating this graph

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Physical Memory

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iFixit, https://www.iﬁxit.com/Teardown/Google+Pixel+XL+Teardown/71237

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iFixit, https://www.iﬁxit.com/Teardown/Google+Pixel+XL+Teardown/71237

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iFixit, https://www.iﬁxit.com/Teardown/Google+Pixel+XL+Teardown/71237

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RAM: Random Access Memory Like a ByteArray(4294967296) Keeps state for the OS and all running apps Physical Memory is a Big ByteArray!

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Allocating Memory

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The allocator’s job is to bridge the gap between ‘Big Graph’ and ‘Big ByteArray’

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The Simplest Allocator Allocate memory in sequence, as requested When you run out of memory, crash! targets.withType().all { compilations.configureEach { compileTaskProvider.configure { compilerOptions.freeCompilerArgs.add("-Xgc=noop") } } }

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0x99 0xfe 0xb0b15c00 0x0465 0x00 0x09 0xcafebabe 0x08675309 0x43 0x06 0x68 0x6d 0x6f 0x79 0x70 0xc0 4016000000000000 0x

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var nextOffset = 160000 0x99 0xfe 0xb0b15c00 0x0465 0x00 0x09 0xcafebabe 0x08675309 0x43 0x06 0x68 0x6d 0x6f 0x79 0x70 0xc0 4016000000000000 0x

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var nextOffset = 160000 val referenceSize = 4 0x99 0xfe 0xb0b15c00 0x0465 0x00 0x09 0xcafebabe 0x08675309 0x43 0x06 0x68 0x6d 0x6f 0x79 0x70 0xc0 4016000000000000 0x

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var nextOffset = 160000 val referenceSize = 4 0x99 0xfe 0xb0b15c00 0x0465 0x00 0x09 0xcafebabe 0x08675309 0x43 0x06 0x68 0x6d 0x6f 0x79 0x70 0xc0 4016000000000000 0x 160000

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var nextOffset = 160000 val referenceSize = 4 10 0x99 0xfe 0xb0b15c00 0x0465 0x00 0x09 0xcafebabe 0x08675309 0x43 0x06 0x68 0x6d 0x6f 0x79 0x70 0xc0 4016000000000000 0x 160000

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var nextOffset = 160000 val referenceSize = 4 10 0x99 0xfe 0xb0b15c00 0x0465 0x00 0x09 0xcafebabe 0x08675309 0x43 0x06 0x68 0x6d 0x6f 0x79 0x70 0xc0 4016000000000000 0x 160000 160010

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var nextOffset = 160000 val referenceSize = 4 10 21 0x99 0xfe 0xb0b15c00 0x0465 0x00 0x09 0xcafebabe 0x08675309 0x43 0x06 0x68 0x6d 0x6f 0x79 0x70 0xc0 4016000000000000 0x 160000 160010

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var nextOffset = 160000 val referenceSize = 4 10 21 0x99 0xfe 0xb0b15c00 0x0465 0x00 0x09 0xcafebabe 0x08675309 0x43 0x06 0x68 0x6d 0x6f 0x79 0x70 0xc0 4016000000000000 0x 160000 160021 160010

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var nextOffset = 160000 val referenceSize = 4 10 21 34 0x99 0xfe 0xb0b15c00 0x0465 0x00 0x09 0xcafebabe 0x08675309 0x43 0x06 0x68 0x6d 0x6f 0x79 0x70 0xc0 4016000000000000 0x 160000 160021 160010

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var nextOffset = 160000 val referenceSize = 4 10 21 34 0x99 0xfe 0xb0b15c00 0x0465 0x00 0x09 0xcafebabe 0x08675309 0x43 0x06 0x68 0x6d 0x6f 0x79 0x70 0xc0 4016000000000000 0x 160000 160021 160034 160010

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var nextOffset = 160000 val referenceSize = 4 10 21 34 39 0x99 0xfe 0xb0b15c00 0x0465 0x00 0x09 0xcafebabe 0x08675309 0x43 0x06 0x68 0x6d 0x6f 0x79 0x70 0xc0 4016000000000000 0x 160000 160021 160034 160010

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var nextOffset = 160000 val referenceSize = 4 10 21 34 39 45 0x99 0xfe 0xb0b15c00 0x0465 0x00 0x09 0xcafebabe 0x08675309 0x43 0x06 0x68 0x6d 0x6f 0x79 0x70 0xc0 4016000000000000 0x 160000 160021 160034 160039 160010

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var nextOffset = 160000 val referenceSize = 4 10 21 34 39 45 56 0x99 0xfe 0xb0b15c00 0x0465 0x00 0x09 0xcafebabe 0x08675309 0x43 0x06 0x68 0x6d 0x6f 0x79 0x70 0xc0 4016000000000000 0x 160000 160021 160034 160039 160045 160010

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var nextOffset = 160056 val referenceSize = 4 0x00027122 0x0002712d 0x99 0xfe 0xb0b15c00 0x0465 0x00 0x09 0xcafebabe 0x08675309 0x43 0x06 0x68 0x6d 0x6f 0x79 0x70 0xc0 4016000000000000 0x 0x000271a0 0x00027115 0x00027115 0x0002712d 0x00027127 0x00027127 0x00027100 0x00027100 0x00027100 0x00027100 0x00027100 0x000271a0 0x000271a0

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0x000271a0 0x00027115 0x00027122 0x00027127 0x0002712d 0x00027100 0x00027100 0x00027100 0x000271a0 0x000271a0 0x00027115 0x0002712d 0x00027127 0x99 0xfe 0xb0b15c00 0x0465 0x00 0x09 0xcafebabe 0x08675309 0x43 0x06 0x68 0x6d 0x6f 0x79 0x70 0xc0 4016000000000000 0x var nextOffset = 160056 val referenceSize = 4 0x00027100 0x00027100

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0x00027100 0x000271a0 0x00027115 0x00027122 0x00027127 0x0002712d 00027100 00027100 00027100 000271a0 000271a0 00027115 0002712d 00027127 99 fe b0b15c00 0465 00 09 cafebabe 4016000000000000 08675309 43 06 68 6d 6f 79 70 c0 0x 0x 0x 0x 0x 0x 0x 0x 0x 0x 0x 0x 0x 0x 0x 0x 0x 0x 0x 0x 0x 0x 0x 0x 0x var nextOffset = 160056 val referenceSize = 4

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00027100 00027100 00027100 000271a0 000271a0 00027115 0002712d 00027127 99 fe b0b15c00 0465 00 09 cafebabe 4016000000000000 08675309 43 06 68 6d 6f 79 70 c0 var nextOffset = 160056 val referenceSize = 4

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Real Allocators They don’t keep everything in the big graph! • Some objects in the graph have no incoming references • Nobody will know if we stop tracking them! You can create temporary objects without running out of memory

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Garbage Collection A batch process to ﬁnd & free unnecessary objects 1. Mark every object you can reach 2. Free the rest Used by the JVM, ART, Kotlin/Native, JavaScript, and Golang

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class NearbyGatorsContent { var list = listOf() override fun onGators(nearbyGators: List) { list = nearbyGators } }

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List size 1 0 NearbyGator name "Lyle" distance 4.57 NearbyGators Content list HomeActivity scope ... model

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List size 1 0 NearbyGator name "Lyle" distance 4.57 NearbyGators Content list NearbyGator name "Smiley" distance 7.64 NearbyGator name "Chompy" distance 9.58 List size 2 0 1 HomeActivity scope ... model

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NearbyGators Content list NearbyGator name "Smiley" distance 7.64 NearbyGator name "Chompy" distance 9.58 List size 2 0 1 HomeActivity scope ... model ✔ ✔ ✔ ✔ ✔

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Reference Counting Each object tracks how many other objects reference it When the count reaches zero, it self-destructs Used by Swift, Python, C++’s std::shared_ptr, and Rust’s Rc

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class NearbyGatorsContent { var array: [NearbyGator] = [] func onGators(array: [NearbyGator]) { self.array = array } }

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NearbyGators Content ref count 1 array NearbyGator ref count 1 name "Lyle" distance 4.57 HomeView ref count 1 model Array ref count 1 size 1 0

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NearbyGators Content ref count 1 array NearbyGator ref count 1 name "Chompy" distance 9.58 NearbyGator ref count 1 name "Smiley" distance 7.64 NearbyGator ref count 1 name "Lyle" distance 4.57 HomeView ref count 1 model Array ref count 1 size 1 0 Array ref count 1 size 1 0 1

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NearbyGators Content ref count 1 array NearbyGator ref count 1 name "Chompy" distance 9.58 NearbyGator ref count 1 name "Smiley" distance 7.64 HomeView ref count 1 model Array ref count 1 size 1 0 1

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NearbyGators Content ref count 1 array NearbyGator ref count 1 name "Chompy" distance 9.58 NearbyGator ref count 1 name "Smiley" distance 7.64 HomeView ref count 1 model Array ref count 1 size 1 0 1 2

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Leaking Memory

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Leaks Wasted counter space wrecks your cooking performance Wasted memory can wreck your app’s performance Impact is most severe for long-running processes: • Servers • Point-of-sale apps

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XCODE TIPS 5

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FLATTEN KOTLIN/NATIVE ALLOCATIONS #1 MaNY OBJECTS SHARE A NODE

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FLATTEN KOTLIN/NATIVE ALLOCATIONS #1 kotlin { targets.withType().all { compilations.configureEach { compileTaskProvider.configure { // This makes the Xcode memory analyzer graphs easier to // understand. Be careful when using this in production; // it's not as stable as the default allocator. // (See KT-68769) compilerOptions.freeCompilerArgs.add("-Xallocator=std") // Work around an issue with the above option! compilerOptions.freeCompilerArgs.add("-opt") } } } }

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FLATTEN KOTLIN/NATIVE ALLOCATIONS #1

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FLATTEN KOTLIN/NATIVE ALLOCATIONS #1 Task :shared:linkDebugFrameworkIosSimulatorArm64 FAILED /Users/jwilson/.gradle/.../kotlinx-coroutines-core is cached (in ~/.konan/kotlin-native-prebuilt-macos-aarch64-2.0.0/...), but its dependency isn't: /Users/jwilson/.konan/.../stdlib $ rm -rf ~/.konan/kotlin-native-prebuilt-macos-aarch64-2.0.0

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FLATTEN KOTLIN/NATIVE ALLOCATIONS #1

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FLATTEN KOTLIN/NATIVE ALLOCATIONS #1 MORE NODES!

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PAY ATTENTION TO ZOOM #2

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PAY ATTENTION TO ZOOM #2 Labeled Nodes

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PAY ATTENTION TO ZOOM #2 Labeled Edges Labeled Nodes

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PRINT DESCRIPTION #3

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PRINT DESCRIPTION #3 THAT’S TOSTRING()

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STACK LOGGING #4

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STACK LOGGING #4

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STACK LOGGING #4

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STACK LOGGING #4

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STACK LOGGING #4

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STACK LOGGING #4

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STACK LOGGING #4 USELESS LABELS

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STACK LOGGING #4 USELESS LABELS

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STACK LOGGING #4

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STACK LOGGING #4

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STACK LOGGING #4 CALL STACK WHEN IT WAS ALLOCATED!

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FORCE GC #5 132 INSTANCEs }

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/** * Call this in debug builds to collect Kotlin objects and chains * of Kotlin + Swift objects. This isn't necessary for correct * application behavior, but it is helpful when doing memory * analysis because it removes unreachable objects. * * This runs a Kotlin GC which may have the side effect of * queueing some Swift objects to be eligible for `deinit()`. * And running that `deinit()` on the main thread will potentially * make some Kotlin objects eligible for collection! */ @OptIn(NativeRuntimeApi::class) object KotlinMemory { fun blockingCollect() { GC.collect() } } FORCE GC #5

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FORCE GC #5 9 INSTANCEs }

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XCODE TIPS 5 FLATTEN KOTLIN/NATIVE ALLOCATIONS PAY ATTENTION TO ZOOM PRINT DESCRIPTION 1. 2. 3. 4. 5. STACK LOGGING FORCE GC

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Memory Leaks on Android

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Just Use LeakCanary It detects leaks automatically: • It knows the lifecycles for common Android objects • If an object is still reachable in the Big Graph after its lifecycle is done, it probably leaked The leak trace shows you what to ﬁx

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YourKit Too Export an .hprof ﬁle from Android Studio Open that in YourKit Much more capable than Android Studio’s heap viewer

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class NearbyGatorsContent( private val gatorsService: GatorsService, ) : GatorsService.Listener { val list = mutableStateListOf() init { gatorsService.addListener(this) } override fun onGators(nearbyGators: List) { list.clear() list.addAll(nearbyGators) } } }

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Memory Leaks on iOS using Kotlin/Native

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Just Use LeakSwift Just joking! iOS doesn’t have a P-Y There’s a couple of libraries but nothing as easy or capable

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class NearbyGatorsContent: ObservableObject, GatorsServiceListener { private let service: GatorsService @Published var array: [NearbyGator] = [] init(service: GatorsService) { self.service = service service.addListener(listener: self) } func onGators(array: [NearbyGator]) { self.array = array } } }

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deinit { service.removeListener(listener: self) } } class NearbyGatorsContent: ObservableObject, GatorsServiceListener { private let service: GatorsService @Published var array: [NearbyGator] = [] init(service: GatorsService) { self.service = service service.addListener(listener: self) } func onGators(array: [NearbyGator]) { self.array = array }

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List size 0 0 GatorsService listeners ... NearbyGators Content ref count 1 service ... HomeView ref count 1 model

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List size 0 0 GatorsService listeners ... NearbyGators Content ref count 1 service ... HomeView ref count 1 model 1

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List size 0 0 GatorsService listeners ... NearbyGators Content ref count 1 service ... 2 HomeView ref count 1 model 1

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List size 0 0 GatorsService listeners ... NearbyGators Content ref count 1 service ... 2 HomeView ref count 1 model 1 1

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List size 0 0 GatorsService listeners ... NearbyGators Content ref count 1 service ... 2 HomeView ref count 1 model 1 1 ✔ ✔

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func onGators(array: [NearbyGator]) { } .array = array private let service: GatorsService @Published var array: [NearbyGator] = [] {abc class NearbyGatorsContent: ObservableObject init(service: GatorsService) { self.service = service service.addListener( listener: )def deinit { service.removeListener( } listener: )ghi GatorsServiceListener }nop self. self self }xxz ,

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private let service: GatorsService @Published var array: [NearbyGator] = [] {abc class NearbyGatorsContent: ObservableObject init(service: GatorsService) { self.service = service service.addListener( )def deinit { service.removeListener( } )ghi }nop }xxz , func onGators(array: [NearbyGator]) { } .array = array self. GatorsServiceListener listener: listener: self self

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func onGators(array: [NearbyGator]) { } .array = array content? private let service: GatorsService @Published var array: [NearbyGator] = [] {abc class NearbyGatorsContent: ObservableObject init(service: GatorsService) { self.service = service service.addListener( )def }xxz )ghi GatorsServiceListener {hij }klm }nop private class Listener : var content: NearbyGatorsContent? = nil deinit { service.removeListener( } listener: listener: self self

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deinit { service.removeListener( } func onGators(array: [NearbyGator]) { } .array = array content? private let service: GatorsService @Published var array: [NearbyGator] = [] {abc class NearbyGatorsContent: ObservableObject private let listener: Listener init(service: GatorsService) { self.service = service service.addListener(listener: listener )def self.listener = Listener() self.listener.content = self }xxz listener: listener )ghi GatorsServiceListener {hij }klm }nop private class Listener : var content: NearbyGatorsContent? = nil

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deinit { service.removeListener( } func onGators(array: [NearbyGator]) { } .array = array content? private let service: GatorsService @Published var array: [NearbyGator] = [] {abc class NearbyGatorsContent: ObservableObject private let listener: Listener init(service: GatorsService) { self.service = service service.addListener(listener: listener )def self.listener = Listener() self.listener.content = self }xxz listener: listener )ghi weak GatorsServiceListener {hij }klm }nop private class Listener : var content: NearbyGatorsContent? = nil

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deinit { service.removeListener( } func onGators(array: [NearbyGator]) { } .array = array content? private let service: GatorsService @Published var array: [NearbyGator] = [] {abc class NearbyGatorsContent: ObservableObject private let listener: Listener init(service: GatorsService) { self.service = service service.addListener(listener: listener )def self.listener = Listener() self.listener.content = self }xxz listener: listener )ghi weak GatorsServiceListener {hij }klm }nop private class Listener : var content: NearbyGatorsContent? = nil

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NearbyGators Content ref count 1 service listener ... List size 0 0 GatorsService listeners ... HomeView ref count 1 model

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NearbyGators Content ref count 1 service listener ... List size 0 0 GatorsService listeners ... HomeView ref count 1 model Listener ref count 1 content

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NearbyGators Content ref count 1 service listener ... List size 0 0 GatorsService listeners ... HomeView ref count 1 model Listener ref count 1 content + 1 weak

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NearbyGators Content ref count 1 service listener ... List size 0 0 GatorsService listeners ... HomeView ref count 1 model 1 Listener ref count 1 content + 1 weak

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NearbyGators Content ref count 1 service listener ... List size 0 0 GatorsService listeners ... HomeView ref count 1 model 1 Listener ref count 1 content 2 + 1 weak

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NearbyGators Content ref count 1 service listener ... List size 0 0 GatorsService listeners ... HomeView ref count 1 model 1 Listener ref count 1 content 2 + 1 weak

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NearbyGators Content ref count 1 service listener ... List size 0 0 GatorsService listeners ... HomeView ref count 1 model 1 Listener ref count 1 content 2 0 + 1 weak

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List size 0 0 GatorsService listeners ... HomeView ref count 1 model 1 Listener ref count 1 content 2 1

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HomeView ref count 1 model Listener ref count 1 content 2 1 0

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HomeView ref count 1 model

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It’s Difﬁcult One big graph of objects with different rules for different objects: • Swift does reference counting • Kotlin does garbage collection

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class Holder { var target: Any? = null } fun createSmallCycle() { val holder = Holder() val array = NSMutableArray() array.addObject(holder) holder.target = array } Retain Cycles without any Swift NSMutableArray ref count 1 size 1 0 Holder target

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It’s not a problem while the objects are still in use The garbage collector can collect cycles as long as every property is declared in Kotlin A cycle* in the Big Graph with at least one NSObject** * ** Anatomy of a Leak

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Avoiding Leaks, Systematically

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How Swift Does It Every property is either an owned reference (default) or one of two other kinds, weak and unowned iOS developers are always thinking about this! It’s as bad as Java developers worrying about null DispatchQueue.main.async { [weak self] in ... }

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How I Avoid Leaks in Kotlin/Native Never reference a Swift object from a Kotlin object If I must break Rule #1: A. Give the referencing Kotlin class a close() function B. That function sets properties to null C. Make sure it gets called RULE #1 RULE #2

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class DisplayLinkTarget( private var displayLink: CADisplayLink?, ) { ... fun close() { displayLink?.invalidate() displayLink = null // Break a reference cycle. } }

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Why Break Cycles From Kotlin?

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Why Break Cycles From Kotlin? Did ya get the latest Kotlin alligators library?

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Did ya get the latest Kotlin alligators library? Yep! But Xcode is mad ’cause it’s leaking memory

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Yep! But Xcode is mad ’cause it’s leaking memory Oh shit

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Oh shit Oh shit

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Oh shit It’s equally valid to break cycles from Swift, or a mix of both! Kotlin that doesn’t leak helps to earn iOS engineers' trust

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Detecting Leaks in Tests We built a LeakWatcher test helper in Redwood Currently JVM-only It uses PhantomReference to check whether an object is referenced val leakWatcher = LeakWatcher { content.listener } content.close() leakWatcher.assertNotLeaked()

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Detecting Leaks in Production We also built a LeakDetector API in Redwood Supports the JVM, Kotlin/Native, and Kotlin/JS It uses WeakReference to check whether an object is referenced leakDetector.watchReference( reference = listener, note = "content listener removed", )

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Take Aways

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Life Comes At You Swiftly Garbage Collection is great LeakCanary is great iOS has neither Every Swift object is a resource you might need to release Xcode can be coerced into helping you

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Valhalla BONUS TOPIC

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Java’s Epic Refactor Kotlin already has a limited version with @JvmInline value classes GOAL: HOW: PLUS: Increase the information density in the JVM’s memory By unifying primitives and references in the type system Better null handling!

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record NearbyGator(String name, double distance) { public }

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record NearbyGator(String name, double distance) { public }

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value public } record NearbyGator(String name, double distance) {

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record NearbyGator(String name, double distance) { public } value

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0 1 2 3 size Array distance name NearbyGator 7.64 String data "Lyle" distance name NearbyGator 9.58 String data "Smiley" 5.31 distance name NearbyGator String data "Chompy" 0 1 2

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0 1 2 3 size Array distance name NearbyGator 7.64 String data "Lyle" distance name 9.58 String data "Smiley" 5.31 distance name String data "Chompy" 0 1 2

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Valhalla Started in 2014 as a research project You can download a build of JDK 23 that has value classes today

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Thanks github.com/swankjesse/memory