Talking trash

Talking Trash Michael Labriola Senior Consultant Digital Primates @mlabriola Page 0 of 59

Who am I? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Page 2 of 59

What are we going to cover? ,[object Object],[object Object],[object Object],[object Object],Page 3 of 59

Disclaimer ,[object Object],[object Object],[object Object],Page 3 of 59

Memories ,[object Object],[object Object],[object Object],[object Object],Page 3 of 59

What is GC ,[object Object],[object Object],[object Object],Page 3 of 59 Memory GC Program Code

Why Proxy? ,[object Object],[object Object],Page 3 of 59

Dangling References ,[object Object],Page 3 of 59 Memory p1 p2 memory = allocate( size ); p1 = memory; p2 = memory; free( memory ); trace( p1.toString() ); trace( p2.toString() );

Double Free ,[object Object],Page 3 of 59 Memory2 memory1 = allocate( size ); free( memory1 ); memory2 = allocate( size ); free( memory1 );

Real Leaks ,[object Object],Page 3 of 59 Memory2 p1 p1 = allocate( size ); p2 = allocate( size ); p1 = p2; Memory1

GC Instead ,[object Object],[object Object],[object Object],Page 3 of 59

GC How ,[object Object],[object Object],Page 3 of 59

Allocation ,[object Object],Page 3 of 59 System Memory 4k 4k 4k GCHeap GC

Pages ,[object Object],Page 3 of 59 4k GC Object A Object B Object C

Much ,[object Object],[object Object],Page 3 of 59

Stack ,[object Object],In this data structure, the only way to get something in the middle is the remove the things above it. Item 1 Item 2 Item 1 Item 2 Item 3

[object Object],Altering the Stack Item 1 Item 2 Item 1 Item 2 Item 3 Item 1 Item 2 Item 4

Local Variable Declaration ,[object Object],function doThing() { var a:int; var b:int; var c:Number; } a b c

Method Calls ,[object Object],function doThing() { var a:int; var b:int; var c:Number; someMethod(); } function someMethod() { var x:int; } a b c x

Method Calls ,[object Object],function doThing() { var a:int; var b:int; var c:Number; someMethod(); } function someMethod() { var x:int; } a b c x doThing

Method Calls ,[object Object],function doThing() { var a:int; var b:int; var c:Number; someMethod1(); someMethod2(); } function someMethod()1 { var x:int; } function someMethod2() { var y:int; } a b c y doThing

Instances ,[object Object],Stack Memory Heap Memory function doThing() { var a:int; var o:Object; o = new Object(); } a o Object A

Instances ,[object Object],Stack Memory Heap Memory function doThing() { var a:int; var o1:Object; o1 = new Object(); doIt( o1 ); } function doIt( o2 ) { var b:int; } Object A a o1 doIt o2 b

Instances ,[object Object],function doThing() { var a:int; var o1:Object; o1 = new Object(); doIt( o1 ); } function doIt( o2 ) { var b:int; } Stack Memory Heap Memory a o1 Object A

Freeing ,[object Object],[object Object],[object Object],Page 3 of 59

Roots ,[object Object],[object Object],[object Object],[object Object],Page 3 of 59

Hybrid ,[object Object],[object Object],Page 3 of 59

Reference Counting ,[object Object],[object Object],Page 3 of 59

Reference Counting ,[object Object],Page 3 of 59 ObjectA a = new ObjectA(); b = new ObjectB(); b.prop = a ; ObjectB a b ObjectA: 2 ObjectB: 1

Reference Counting ,[object Object],Page 3 of 59 ObjectA a = new ObjectA(); b = new ObjectB(); b.prop = a; a = null; ObjectB a b ObjectA: 1 ObjectB: 1

Reference Counting ,[object Object],Page 3 of 59 ObjectA a = new ObjectA(); b = new ObjectB(); b.prop = a; b = null; ObjectB a b ObjectA: 2 ObjectB: 0

Reference Counting ,[object Object],Page 3 of 59 ObjectA a = new ObjectA(); b = new ObjectB(); b.prop = a; a = b = null; ObjectB a b ObjectA: 1 ObjectB: 0

Circular Reference ,[object Object],Page 3 of 59 ObjectA a = new ObjectA(); b = new ObjectB(); b.prop = a; a.prop = b; a = b = null; ObjectB a b ObjectA: 1 ObjectB: 1

Reference Counting Issues ,[object Object],[object Object],[object Object],[object Object],Page 3 of 59

Frequent Allocations ,[object Object],[object Object],Page 3 of 59

Missing Stack Count ,[object Object],Stack Memory method x Page 3 of 59 ObjectA a = new ObjectA(); var x = a; a = null; trace( x.someProp ); ObjectA: 0

Zero Count Table ,[object Object],Page 3 of 59 a = new ObjectA(); var x = a; a = null; trace( x ); ObjectA: 0 Zero Count Table Stack Memory method x ObjectA

Zero Count Table ,[object Object],Page 3 of 59 ObjectA Zero Count Table ObjectB ObjectC Stack Memory method x

Back to Circles ,[object Object],[object Object],[object Object],Page 3 of 59

Mark and Sweep ,[object Object],[object Object],Page 3 of 59

Marking ,[object Object],Page 3 of 59 Object A Object Object Object Object Object Object Object Object Object Object Object

Remainder ,[object Object],Page 3 of 59 Object A Object Object Object Object Object Object Object Object Object Object Object

Tangent – Weak References ,[object Object],[object Object],[object Object],[object Object],[object Object],Page 3 of 59

Weak Reference ,[object Object],Page 3 of 59 Object A Object Object Object Object Object Object Object Object Object Object

Tangent – Weak References ,[object Object],[object Object],[object Object],[object Object],Page 3 of 59

Back on Track ,[object Object],[object Object],[object Object],Page 3 of 59

Work Queue ,[object Object],Page 3 of 59 Work Queue Object A Object B

Hello Complexity ,[object Object],Page 3 of 59 Object A Parent Object Object Child

Tri-Color ,[object Object],[object Object],[object Object],[object Object],[object Object],Page 3 of 59

Work Queue Start ,[object Object],Page 3 of 59 Work Queue Object A Object B

Queue Progress ,[object Object],Page 3 of 59 Work Queue Object B

New Addition ,[object Object],Page 3 of 59 Work Queue Object B O1 O2 O3 O4 Object B Object Object Object Object

Added to the Queue ,[object Object],Page 3 of 59 Work Queue Object B O1 O2 O1 O2 O3 O4 Object B Object Object Object Object

Being Conservative ,[object Object],[object Object],[object Object],Page 3 of 59

Pointer or Integer ,[object Object],[object Object],[object Object],[object Object],[object Object],Page 3 of 59

Minor Leaks ,[object Object],[object Object],[object Object],Page 3 of 59

Moving On ,[object Object],[object Object],[object Object],[object Object],Page 3 of 59

Controlling GC ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Page 3 of 59

Imminence ,[object Object],[object Object],[object Object],Page 3 of 59 Pause Marking 0 Imminence Increasing 1

Something Incubating ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Page 3 of 59

Pause Now ,[object Object],[object Object],[object Object],Page 3 of 59 Pause Marking 0 Imminence Increasing 1

Wait, pause now? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Page 3 of 59

Advice Examples ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Page 3 of 59

Giving Back ,[object Object],Page 3 of 59 System Memory 4k 4k 4k GCHeap GC

[object Object],Fragmentation Page 3 of 59 Object Object Object Pages are allocated and space for objects allocated. Object Object Object Object Object Object Some objects collected, some new ones created Object Object Object Net result: Even though we did collect objects, we cant release any pages. Object Object Time

[object Object],[object Object],Fragmentation Page 3 of 59

[object Object],[object Object],[object Object],Pure Speculation Page 3 of 59

[object Object],Fragmentation Page 3 of 59 Object Object Object Pages are allocated and space for objects allocated. Object Object Object Object Object Object Some objects collected, some new ones created Object Object Objects are moved into a single page. Other pages could be freed. Time Object Object Object

[object Object],[object Object],[object Object],[object Object],[object Object],Objects, where? Page 3 of 59

[object Object],[object Object],[object Object],[object Object],[object Object],Exact Tracing Page 3 of 59

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Exact Tracing Page 3 of 59

[object Object],[object Object],[object Object],Why Else? Page 3 of 59

[object Object],[object Object],[object Object],Generational Page 3 of 59

[object Object],Generational Page 3 of 59 Object Object Object New objects live in this region. GC checks this region often for reaping. Object Object Object Object Object The oldest objects in the system are checked infrequently Object Object Object Object Age

[object Object],Generational Page 3 of 59 Object Object Object This region is continually reused Object Object Object Object Object Object Objects are copied if they are referenced from older memory Object The oldest objects change infrequently Object Object Object Object Object Movement

[object Object],[object Object],[object Object],Reference Count No More Page 3 of 59

Contact Information Michael Labriola http://twitter.com/mlabriola Page 59 of 59

Talking trash

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Talking trash