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.NET [Core] Internals Garbage Collection Robert Haken software & cloud architect, HAVIT, s.r.o. [email protected], @RobertHaken, https://knowledge-base.havit.cz + .eu Microsoft MVP: Development, MCT, MCPD: Web, MCSE: Cloud

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Page 1: NET [Core] Internals Garbage Collection...2019/01/17  · Garbage Collection Steps 1. Trigger 2. Suspend managed threads (vs. concurrent GC) 3. User-thread runs GC code 4. Select

.NET [Core] InternalsGarbage Collection

Robert Hakensoftware & cloud architect, HAVIT, [email protected], @RobertHaken, https://knowledge-base.havit.cz + .euMicrosoft MVP: Development, MCT, MCPD: Web, MCSE: Cloud

Page 2: NET [Core] Internals Garbage Collection...2019/01/17  · Garbage Collection Steps 1. Trigger 2. Suspend managed threads (vs. concurrent GC) 3. User-thread runs GC code 4. Select

AGENDA

Architektura paměti .NET aplikací

Managed Heap a Garbage Collection

Roots

Generations

Large Object Heap

Finalization, IDisposable

Další optimalizace GC

Page 3: NET [Core] Internals Garbage Collection...2019/01/17  · Garbage Collection Steps 1. Trigger 2. Suspend managed threads (vs. concurrent GC) 3. User-thread runs GC code 4. Select

DEMO

Heap Inspection (02-ManagedHeap)

Page 4: NET [Core] Internals Garbage Collection...2019/01/17  · Garbage Collection Steps 1. Trigger 2. Suspend managed threads (vs. concurrent GC) 3. User-thread runs GC code 4. Select

Architektura paměti .NET aplikací

Instrukční paměť

Zásobník (Stack)

Halda (Heap)

–Managed Heap (.NET, Garbage Collector)

–Native Heap (Unmanaged Resources)

Page 5: NET [Core] Internals Garbage Collection...2019/01/17  · Garbage Collection Steps 1. Trigger 2. Suspend managed threads (vs. concurrent GC) 3. User-thread runs GC code 4. Select

Halda (ManagedHeap)

Garbage Collector ~ 1959 LISP

Garbage Collection–překročení thresholdugenerace při alokaci

–system-wide memory pressure

–GC.Collect() API (never-ever!)

bump pointer allocation vs. free-list

sesypání, update referencí

Page 6: NET [Core] Internals Garbage Collection...2019/01/17  · Garbage Collection Steps 1. Trigger 2. Suspend managed threads (vs. concurrent GC) 3. User-thread runs GC code 4. Select
Page 7: NET [Core] Internals Garbage Collection...2019/01/17  · Garbage Collection Steps 1. Trigger 2. Suspend managed threads (vs. concurrent GC) 3. User-thread runs GC code 4. Select

DEMO

Garbage Collection (03-SimpleGarbageCollection)

Page 8: NET [Core] Internals Garbage Collection...2019/01/17  · Garbage Collection Steps 1. Trigger 2. Suspend managed threads (vs. concurrent GC) 3. User-thread runs GC code 4. Select

Roots

kořeny grafu objektů pro zjištění dosažitelnosti

– zásobník (lokální proměnné, parametry metod)

– GCHandles

• globální statické fieldy

• pinnedobjects

• ...

– F-reachablequeue

(WeakReference)

Page 9: NET [Core] Internals Garbage Collection...2019/01/17  · Garbage Collection Steps 1. Trigger 2. Suspend managed threads (vs. concurrent GC) 3. User-thread runs GC code 4. Select

DEMO

GC Roots (04-GCRoots)

Page 10: NET [Core] Internals Garbage Collection...2019/01/17  · Garbage Collection Steps 1. Trigger 2. Suspend managed threads (vs. concurrent GC) 3. User-thread runs GC code 4. Select

Generations

výkonová optimalizace

soustředí se objekty s krátkou životností

Gen 0 – nové, Gen 1 & 2 – přežily 1/více-krát

Gen 0 + 1 = ephemeral segment („fixed“ size)

Gen 2 = variablesize

Page 11: NET [Core] Internals Garbage Collection...2019/01/17  · Garbage Collection Steps 1. Trigger 2. Suspend managed threads (vs. concurrent GC) 3. User-thread runs GC code 4. Select

Generations

Page 12: NET [Core] Internals Garbage Collection...2019/01/17  · Garbage Collection Steps 1. Trigger 2. Suspend managed threads (vs. concurrent GC) 3. User-thread runs GC code 4. Select

DEMO

Generations (05-Generations)

Page 13: NET [Core] Internals Garbage Collection...2019/01/17  · Garbage Collection Steps 1. Trigger 2. Suspend managed threads (vs. concurrent GC) 3. User-thread runs GC code 4. Select

Finalization

explicitní úklid unmanaged zdrojů

Finalize() ~ C# destructor

Finalization Queue=> do Gen 1

F-reachableQueue

Finalization Thread

IDisposable, ResourceWrapper pattern

Page 14: NET [Core] Internals Garbage Collection...2019/01/17  · Garbage Collection Steps 1. Trigger 2. Suspend managed threads (vs. concurrent GC) 3. User-thread runs GC code 4. Select

DEMO

Page 15: NET [Core] Internals Garbage Collection...2019/01/17  · Garbage Collection Steps 1. Trigger 2. Suspend managed threads (vs. concurrent GC) 3. User-thread runs GC code 4. Select

LargeObjectHeap

výkonová optimalizace

objekty větší než 85 000 bytů (default)

součást Gen 2 collection

nesetřásá se (NET 4.5.1+ lze jednorázově)

Free List

Page 16: NET [Core] Internals Garbage Collection...2019/01/17  · Garbage Collection Steps 1. Trigger 2. Suspend managed threads (vs. concurrent GC) 3. User-thread runs GC code 4. Select

DEMO

Large Object Heap (06-LargeObjectHeap)

Page 17: NET [Core] Internals Garbage Collection...2019/01/17  · Garbage Collection Steps 1. Trigger 2. Suspend managed threads (vs. concurrent GC) 3. User-thread runs GC code 4. Select

Garbage Collection Steps

1. Trigger

2. Suspend managed threads (vs. concurrent GC)

3. User-thread runs GC code

4. Select generation

5. Mark (GCRoots, Remembered Sets vs. Card Tables)

6. Plan (Compact/Sweep)

7. Sweep / Compact + Relocate

8. Resume managed threads

Page 18: NET [Core] Internals Garbage Collection...2019/01/17  · Garbage Collection Steps 1. Trigger 2. Suspend managed threads (vs. concurrent GC) 3. User-thread runs GC code 4. Select

Verze GarbageCollectoru

Workstation (lag) vs. server (throughput)configuration/runtime/gcServerenabled="true|false"

Background GC (NET4 wksonly, NET4.5 svr)

configuration/runtime/gcConcurrentenabled="true|false"

Objekt >2GB (x64, NET4.5)

LOH Free ListsOptimization (NET4.5)

LOH HeapBalancing (NET4.5)

LOH Compaction, explicit (NET4.5.1)

Page 19: NET [Core] Internals Garbage Collection...2019/01/17  · Garbage Collection Steps 1. Trigger 2. Suspend managed threads (vs. concurrent GC) 3. User-thread runs GC code 4. Select

Q & ARobert Haken

MVP ASP.NET/IIS, MCT

@RobertHaken, [email protected]

http://knowledge-base.havit.cz

mailto:[email protected]

Garbage Collection unter.NET Garbage Collection Optimierung Finalization Resurrection

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