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![.NET SUMMIT BELARUS 2017 #DOTNETSUMMITBY | @DINAGOZIL
POOL, BUFFER AND REUSE EXPENSIVE OBJECTS
▸ Pool expensive or large objects
instead of returning them to GC
▸ Many OSS pools out there
▸ For large arrays (e.g. byte[]) may use
System.Buffers
▸ A large preallocated buffer which
is sliced into small parts
46
https://github.com/dotnet/corefx/blob/master/src/System.Buffers/tests/ArrayPool/UnitTests.cs](https://image.slidesharecdn.com/lookmommynogc-170923131828/75/Look-Mommy-no-GC-NET-Summit-2017-46-2048.jpg)
Uploaded byDina Goldshtein
Look Mommy, no GC! (.NET Summit 2017)
Dina Goldshtein's presentation at the .NET Summit Belarus 2017 focuses on memory management in .NET applications, discussing memory allocation, identification of performance issues, and techniques to profile and analyze memory usage. Key recommendations include minimizing garbage collection calls, preferring value types to reduce memory footprint, and utilizing object pooling for expensive objects. The presentation emphasizes the importance of measuring and optimizing memory usage to improve application performance.
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Look Mommy, no GC! (.NET Summit 2017)
- 1. LOOK MOMMY, NOGC! DINA GOLDSHTEIN, @DINAGOZIL
- 2. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL AGENDA ▸ Motivation ▸ Identifying memory traffic problems ▸ Specific code patterns ▸ General tips and tricks 2
- 3. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL IT’S NOT THAT SIMPLE ▸ Memory allocations are cheap ▸ But not free ▸ And have side effects ▸ Don’t forget to think about the memory 3
- 4. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL THIS ISN’T JUST THEORY 4
- 5. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL THIS ISN’T JUST THEORY 5
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- 7. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL PERFORMANCE COUNTERS ▸ Provide numeric performance information about the system ▸ Located in different areas in the system - disk, .NET, networking, OS objects ▸ Available on-demand using built-in tools like perfmon and typeperf ▸ Can write your own but that’s not the topic of our talk… 7
- 8. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL PERFMON 8
- 9. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL DIVE DEEPER WITH EVENT TRACING FOR WINDOWS ▸ High-speed logging framework supporting more than 100K structured messages per second ▸ .NET, drivers, services, third party components ▸ Can be turned on on-demand while running ▸ Very small overhead ▸ Can write your own but that’s not the topic of our talk… 9
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- 11. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL STATIC CODE ANALYSIS ▸ Can detect code issues while coding without running the application ▸ Usually based on pattern-detection ▸ Undisposed IDisposable-s ▸ Inefficient String concatenations ▸ Wrong number of “dynamic” parameters ▸ ReSharper, Visual Studio, and more 11
- 12. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL TIPS IN VS 12
- 13. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL DYNAMIC MEMORY PROFILING ▸ Dynamic analysis can help uncover more subtle scenarios ▸ Can collect temporal information ▸ Managed and unmanaged memory leaks ▸ Lots of commercial tools available: .NET Memory Profiler, ANTS, dotMemory… 13
- 14. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL .NET MEMORY PROFILER AND MEMORY LEAKS 14
- 15. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL WHO’S HOLDING MY OBJECTS? 15
- 16.
- 17. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL GARBAGE, GARBAGE EVERYWHERE 17
- 18. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL STRUCTS, COMPARISONS AND WHAT’S BETWEEN THEM ▸ We have a data structure containing a single int value ▸ How long does it take to search an element in a list of such data structures? ▸ Different implementations ▸ Default comparison ▸ Override Equals ▸ Implement IEquatable 18
- 19.
- 20. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL RESULTS 20
- 21. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL HOW DOES SEARCHING WORK? 21
- 22. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL HOW DOES COMPARING WORK? 22
- 23. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL WHAT’S THE DIFFERENCE? 23 …
- 24. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL OBJECT EQUALITY COMPARER 24
- 25. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL GENERIC EQUALITY COMPARER 25
- 26. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL WHAT’S TAKING ALL THE TIME? 26
- 27. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL REFLECTION IS EXPENSIVE 27
- 28. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL LAMBDAS AND CLOSURES 28
- 29.
- 30. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL THE RESULTS 30
- 31. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL IT’S ALL ABOUT THE ALLOCATIONS 31
- 32. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL UNDER THE HOOD - AN ALLOCATION FOR EACH CAPTURE 32
- 33. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL UNDER THE HOOD - NO CAPTURING; HENCE, NO ALLOCATION! 33
- 34. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL UNDER THE HOOD - NO DATA; HENCE, NO ALLOCATION! 34
- 35. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL UNDER THE HOOD - BUG 🐞 35
- 36. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL THE RESULTS 36
- 37.
- 38. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL RESULTS 38
- 39.
- 40. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL DON’T CALL GC.COLLECT() ▸ You have a large heap. Don’t make it worse by frequent calls to full GC which is going to take a long time. ▸ Instead, use what we learned to reduce memory usage ▸ And don’t forget to remove debugging code from production 40
- 41. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL THIS IS NOT A DRILL 41
- 42. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL FAMOUS LAST WORDS 42
- 43. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL AN (UN)FORTUNATE COINCIDENCE 43
- 44. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL PREFER VALUE TYPES ▸ Value types (structs) have a compact memory layout, and can be embedded in their parent object, making cache’s life easier and generally reducing footprint 44
- 45. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL BASED ON A REAL STORY 45
- 46. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL POOL, BUFFER AND REUSE EXPENSIVE OBJECTS ▸ Pool expensive or large objects instead of returning them to GC ▸ Many OSS pools out there ▸ For large arrays (e.g. byte[]) may use System.Buffers ▸ A large preallocated buffer which is sliced into small parts 46 https://github.com/dotnet/corefx/blob/master/src/System.Buffers/tests/ArrayPool/UnitTests.cs
- 47. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL HARD TO WATCH 47
- 48. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL AVOID FINALIZATION ▸ Finalizers run at some point after the object is no longer referenced by the application (non-deterministic) ▸ Finalizers run on a separate thread and create potential concurrency issues ▸ Finalization prolongs object lifetime and can create leaks if finalizers don’t complete quickly enough ▸ Better to use deterministic resource management (IDisposable) 48
- 49. .NET SUMMIT BELARUS2017 #DOTNETSUMMITBY | @DINAGOZIL SUMMARY ▸ Although a single memory allocation is extremely fast, it adds up ▸ All based on real questions, stories and bugs ▸ Don’t overcomplicate where it’s not needed ▸ Measure ▸ And optimize… ▸ DIY: https://github.com/dinazil/look-mommy-no-gc 49
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