SlideShare ist ein Scribd-Unternehmen logo
1 von 42
Downloaden Sie, um offline zu lesen
Let’s refresh our memory!
Memory management in .NET
Maarten Balliauw
@maartenballiauw
.NET runtime
Manages execution of programs
Just-in-time compilation: Intermediate Language (IL) ->machine code
Type safety
Exception handling
Security
Thread management
Memory management
Garbage collection (GC)
Garbage Collector
Memory management and GC
“Virtually unlimited memory for our applications”
Big chunk of memory pre-allocated
Runtime manages allocation in that chunk
Garbage Collector (GC) reclaims unused memory, making it available again
.NET memory management 101
Memory allocation
Objects allocated in “managed heap” (big chunk of memory)
Allocating memory is fast, it’s just adding a pointer
Some unmanaged memory is also consumed (not GC-ed)
.NET CLR, Dynamic libraries, Graphics buffer, …
Memory release or “Garbage Collection” (GC)
Generations
Large Object Heap
.NET memory management 101
Memory allocation
Memory release or “Garbage Collection” (GC)
GC releases objects no longer in use by examining application roots
GC builds a graph of all the objects that are reachable from these roots
Object unreachable? Remove object, release memory, compact heap
Takes time to scan all objects!
Generations
Large Object Heap
.NET memory management 101
Memory allocation
Memory release or “Garbage Collection” (GC)
Generations
Large Object Heap
Generation 0 Generation 1 Generation 2
Short-lived objects (e.g. Local
variables)
In-between objects Long-lived objects (e.g. App’s
main form)
.NET memory management 101
Memory allocation
Memory release or “Garbage Collection” (GC)
Generations
Large Object Heap (LOH)
Special segment for large objects (>85KB)
Collected only during full garbage collection
Not compacted (by default) -> fragmentation!
Fragmentation can cause OutOfMemoryException
The .NET garbage collector
Runs very often for gen0
Short-lived objects, few references, fast to clean
Local variable
Web request/response
Higher generation
Usually more references, slower to clean
GC pauses the running application to do its thing
Usually short, except when not…
Background GC (enabled by default)
Concurrent with application threads
May still introduce short locks/pauses, usually just for one thread
The .NET garbage collector
When does it run? Vague… But usually:
Out of memory condition – when the system fails to allocate or re-allocate memory
After some significant allocation – if X memory is allocated since previous GC
Failure of allocating some native resources – internal to .NET
Profiler – when triggered from profiler API
Forced – when calling methods on System.GC
Application moves to background
GC is not guaranteed to run
http://blogs.msdn.com/b/oldnewthing/archive/2010/08/09/10047586.aspx
http://blogs.msdn.com/b/abhinaba/archive/2008/04/29/when-does-the-net-compact-framework-garbage-collector-run.aspx
Helping the GC, avoid pauses
Optimize allocations (use struct when it makes sense, Span<T>, object pooling)
Don’t allocate at all
Make use of IDisposable / using statement
Clean up references, giving the GC an easy job
Weak references
Allow the GC to collect these objects, no need for checks
Finalizers
Beware! Moved to finalizer queue -> always gen++
Helping the GC
DEMO
https://github.com/maartenba/memory-demos
Allocations
When is memory allocated?
Not for value types (int, bool, struct, decimal, enum, float, byte, long, …)
Allocated on stack, not on heap
Not managed by garbage collector
For reference types
When you new
When you load data into a variable, object, property, ...
Hidden allocations!
Boxing!
Put an int in a box
Take an int out of a box
Lambda’s/closures
Allocate compiler-generated
DisplayClass to capture state
Params arrays
And more!
int i = 42;
// boxing - wraps the value type in an "object box"
// (allocating a System.Object)
object o = i;
// unboxing - unpacking the "object box" into an int again
// (CPU effort to unwrap)
int j = (int)o;
How to find them?
Past experience
Intermediate Language (IL)
Profiler
“Heap allocations viewer”
ReSharper Heap Allocations Viewer plugin
Roslyn’s Heap Allocation Analyzer
Don’t do premature optimization – measure!
Hidden allocations
DEMO
https://github.com/maartenba/memory-demos
ReSharper Heap Allocations Viewer plugin
Roslyn’s Heap Allocation Analyzer
Don’t optimize what
should not be
optimized.
Measure!
We know when allocations are done...
...but perhaps these don’t matter.
Measure!
How frequently are we allocating?
How frequently are we collecting?
What generation do we end up on?
Are our allocations introducing pauses?
www.jetbrains.com/dotmemory (and www.jetbrains.com/dottrace)
Always Be Measuring
DEMO
https://github.com/maartenba/memory-demos
Object pools / object re-use
If it make sense, re-use objects
Fewer allocations, fewer objects for the GC to scan
Fewer memory traffic that can trigger a full GC
Object pooling - object pool pattern
Create a pool of objects that can be cleaned and re-used
https://www.codeproject.com/articles/20848/c-object-pooling
“Optimize ASP.NET Core” - https://github.com/aspnet/AspLabs/issues/3
Garbage Collector & Allocations
GC is optimized for high memory traffic in short-lived objects
Use that knowledge! Don’t fear allocations!
Don’t optimize what should not be optimized…
GC is the concept that makes .NET / C# tick – use it!
Know when allocations happen
GC is awesome
Gen2 collection that stop the world not so much…
Measure!
Strings
Strings are objects
.NET tries to make them look like a value type, but they are a reference type
Read-only collection of char
Length property
A bunch of operator overloading
Allocated on the managed heap
var a = new string('-', 25);
var b = a.Substring(5);
var c = httpClient.GetStringAsync("http://blog.maartenballiauw.be");
String literals
Are all strings on the heap? Are all strings duplicated?
var a = "Hello, World!";
var b = "Hello, World!";
Console.WriteLine(a == b);
Console.WriteLine(Object.ReferenceEquals(a, b));
Prints true twice. So “Hello World” only in memory once?
Portable Executable (PE)
#UserStrings
DEMO
https://github.com/maartenba/memory-demos
String literals in #US
Compile-time optimization
Store literals only once in PE header metadata stream ECMA-335 standard, section II.24.2.4
Reference literals (IL: ldstr)
var a = Console.ReadLine();
var b = Console.ReadLine();
Console.WriteLine(a == b);
Console.WriteLine(Object.ReferenceEquals(a, b));
String duplicates
Any .NET application has them (System.Globalization duplicates quite a few)
Are they bad?
.NET GC is fast for short-lived objects, so meh.
Don’t waste memory with string duplicates on gen2
(but: it’s okay to have strings there)
String interning
Store (and read) strings from the intern pool
Simply call String.Intern when “allocating” or reading the string
Scans intern pool and returns reference
var url = "http://blog.maartenballiauw.be";
var stringList = new List<string>();
for (int i = 0; i < 1000000; i++)
{
stringList.Add(string.Intern(url + "/"));
}
String interning caveats
Why are not all strings interned by default?
CPU vs. memory
Not on the heap but on intern pool
No GC on intern pool – all strings in memory for AppDomain lifetime!
Rule of thumb
Lot of long-lived, few unique -> interning good
Lot of long-lived, many unique -> no benefit, memory growth
Lot of short-lived -> trust the GC
Measure!
Exploring the heap
for fun and profit
How would you do it...
Build a managed type system, store in memory, CPU/memory friendly
Probably:
Store type info (what’s in there, what’s the offset of fieldN, …)
Store field data (just data)
Store method pointers (“who you gonna call?”)
Inheritance information
Stuff on the Stack
Stuff on the Managed Heap
(scroll down for more...)
.NET memory is like a database
Pointer to an “instance”
Instance
Pointer to Runtime Type Information (RTTI)
Field values (which can be pointers in turn)
RunTime Type Information
Interface addresses
Instance method addresses
Static method addresses
…
Theory is nice...
Microsoft.Diagnostics.Runtime (ClrMD)
“ClrMD is a set of advanced APIs for programmatically inspecting a crash dump of
a .NET program much in the same way that the SOS Debugging Extensions (SOS)
do. This allows you to write automated crash analysis for your applications as well
as automate many common debugger tasks. In addition to reading crash dumps
ClrMD also allows supports attaching to live processes.”
“LINQ-to-heap”
Maarten’s definition
ClrMD
DEMO
https://github.com/maartenba/memory-demos
But... Why?
Programmatic insight into memory space of a running project
Unit test critical paths and assert behavior (did we clean up what we expected?)
Capture memory issues in running applications
Other options in this space
dotMemory Unit (JetBrains)
Benchmark.NET
Conclusion
Conclusion
Garbage Collector (GC) optimized for high memory traffic + short-lived objects
Don’t fear allocations! But beware of gen2 “stop the world”
String interning when lot of long-lived, few unique
Don’t optimize what should not be optimized…
Measure!
Using a profiler/memory analysis tool
ClrMD to automate inspections
dotMemory Unit, Benchmark.NET, … to profile unit tests
Blog series: https://blog.maartenballiauw.be
.NET Internals: stack
memory management
Nikolay Balakin
16:05 – Track 2
Thank you!
http://blog.maartenballiauw.be
@maartenballiauw

Más contenido relacionado

Was ist angesagt?

JavaOne 2012 - JVM JIT for Dummies
JavaOne 2012 - JVM JIT for DummiesJavaOne 2012 - JVM JIT for Dummies
JavaOne 2012 - JVM JIT for DummiesCharles Nutter
 
Millions quotes per second in pure java
Millions quotes per second in pure javaMillions quotes per second in pure java
Millions quotes per second in pure javaRoman Elizarov
 
Java Serialization Facts and Fallacies
Java Serialization Facts and FallaciesJava Serialization Facts and Fallacies
Java Serialization Facts and FallaciesRoman Elizarov
 
An Introduction to JVM Internals and Garbage Collection in Java
An Introduction to JVM Internals and Garbage Collection in JavaAn Introduction to JVM Internals and Garbage Collection in Java
An Introduction to JVM Internals and Garbage Collection in JavaAbhishek Asthana
 
Understanding Java Garbage Collection
Understanding Java Garbage CollectionUnderstanding Java Garbage Collection
Understanding Java Garbage CollectionAzul Systems Inc.
 
Fast as C: How to Write Really Terrible Java
Fast as C: How to Write Really Terrible JavaFast as C: How to Write Really Terrible Java
Fast as C: How to Write Really Terrible JavaCharles Nutter
 
Beyond JVM - YOW! Sydney 2013
Beyond JVM - YOW! Sydney 2013Beyond JVM - YOW! Sydney 2013
Beyond JVM - YOW! Sydney 2013Charles Nutter
 
Down the Rabbit Hole: An Adventure in JVM Wonderland
Down the Rabbit Hole: An Adventure in JVM WonderlandDown the Rabbit Hole: An Adventure in JVM Wonderland
Down the Rabbit Hole: An Adventure in JVM WonderlandCharles Nutter
 
The Year of JRuby - RubyC 2018
The Year of JRuby - RubyC 2018The Year of JRuby - RubyC 2018
The Year of JRuby - RubyC 2018Charles Nutter
 
Java Garbage Collection - How it works
Java Garbage Collection - How it worksJava Garbage Collection - How it works
Java Garbage Collection - How it worksMindfire Solutions
 
Ruby Performance - The Last Mile - RubyConf India 2016
Ruby Performance - The Last Mile - RubyConf India 2016Ruby Performance - The Last Mile - RubyConf India 2016
Ruby Performance - The Last Mile - RubyConf India 2016Charles Nutter
 
Why GC is eating all my CPU?
Why GC is eating all my CPU?Why GC is eating all my CPU?
Why GC is eating all my CPU?Roman Elizarov
 
JVM Garbage Collection Tuning
JVM Garbage Collection TuningJVM Garbage Collection Tuning
JVM Garbage Collection Tuningihji
 
JVM for Dummies - OSCON 2011
JVM for Dummies - OSCON 2011JVM for Dummies - OSCON 2011
JVM for Dummies - OSCON 2011Charles Nutter
 
JRuby and Invokedynamic - Japan JUG 2015
JRuby and Invokedynamic - Japan JUG 2015JRuby and Invokedynamic - Japan JUG 2015
JRuby and Invokedynamic - Japan JUG 2015Charles Nutter
 
JavaOne 2011 - JVM Bytecode for Dummies
JavaOne 2011 - JVM Bytecode for DummiesJavaOne 2011 - JVM Bytecode for Dummies
JavaOne 2011 - JVM Bytecode for DummiesCharles Nutter
 
JVM Mechanics: When Does the JVM JIT & Deoptimize?
JVM Mechanics: When Does the JVM JIT & Deoptimize?JVM Mechanics: When Does the JVM JIT & Deoptimize?
JVM Mechanics: When Does the JVM JIT & Deoptimize?Doug Hawkins
 
Java Performance Tuning
Java Performance TuningJava Performance Tuning
Java Performance TuningMinh Hoang
 

Was ist angesagt? (20)

JavaOne 2012 - JVM JIT for Dummies
JavaOne 2012 - JVM JIT for DummiesJavaOne 2012 - JVM JIT for Dummies
JavaOne 2012 - JVM JIT for Dummies
 
Java Performance Tuning
Java Performance TuningJava Performance Tuning
Java Performance Tuning
 
Millions quotes per second in pure java
Millions quotes per second in pure javaMillions quotes per second in pure java
Millions quotes per second in pure java
 
Java Serialization Facts and Fallacies
Java Serialization Facts and FallaciesJava Serialization Facts and Fallacies
Java Serialization Facts and Fallacies
 
An Introduction to JVM Internals and Garbage Collection in Java
An Introduction to JVM Internals and Garbage Collection in JavaAn Introduction to JVM Internals and Garbage Collection in Java
An Introduction to JVM Internals and Garbage Collection in Java
 
Understanding Java Garbage Collection
Understanding Java Garbage CollectionUnderstanding Java Garbage Collection
Understanding Java Garbage Collection
 
Fast as C: How to Write Really Terrible Java
Fast as C: How to Write Really Terrible JavaFast as C: How to Write Really Terrible Java
Fast as C: How to Write Really Terrible Java
 
Beyond JVM - YOW! Sydney 2013
Beyond JVM - YOW! Sydney 2013Beyond JVM - YOW! Sydney 2013
Beyond JVM - YOW! Sydney 2013
 
Down the Rabbit Hole: An Adventure in JVM Wonderland
Down the Rabbit Hole: An Adventure in JVM WonderlandDown the Rabbit Hole: An Adventure in JVM Wonderland
Down the Rabbit Hole: An Adventure in JVM Wonderland
 
The Year of JRuby - RubyC 2018
The Year of JRuby - RubyC 2018The Year of JRuby - RubyC 2018
The Year of JRuby - RubyC 2018
 
Java Garbage Collection - How it works
Java Garbage Collection - How it worksJava Garbage Collection - How it works
Java Garbage Collection - How it works
 
Ruby Performance - The Last Mile - RubyConf India 2016
Ruby Performance - The Last Mile - RubyConf India 2016Ruby Performance - The Last Mile - RubyConf India 2016
Ruby Performance - The Last Mile - RubyConf India 2016
 
Why GC is eating all my CPU?
Why GC is eating all my CPU?Why GC is eating all my CPU?
Why GC is eating all my CPU?
 
JVM Garbage Collection Tuning
JVM Garbage Collection TuningJVM Garbage Collection Tuning
JVM Garbage Collection Tuning
 
JVM for Dummies - OSCON 2011
JVM for Dummies - OSCON 2011JVM for Dummies - OSCON 2011
JVM for Dummies - OSCON 2011
 
JRuby and Invokedynamic - Japan JUG 2015
JRuby and Invokedynamic - Japan JUG 2015JRuby and Invokedynamic - Japan JUG 2015
JRuby and Invokedynamic - Japan JUG 2015
 
Down the Rabbit Hole
Down the Rabbit HoleDown the Rabbit Hole
Down the Rabbit Hole
 
JavaOne 2011 - JVM Bytecode for Dummies
JavaOne 2011 - JVM Bytecode for DummiesJavaOne 2011 - JVM Bytecode for Dummies
JavaOne 2011 - JVM Bytecode for Dummies
 
JVM Mechanics: When Does the JVM JIT & Deoptimize?
JVM Mechanics: When Does the JVM JIT & Deoptimize?JVM Mechanics: When Does the JVM JIT & Deoptimize?
JVM Mechanics: When Does the JVM JIT & Deoptimize?
 
Java Performance Tuning
Java Performance TuningJava Performance Tuning
Java Performance Tuning
 

Ähnlich wie DotNetFest - Let’s refresh our memory! Memory management in .NET

Exploring .NET memory management - A trip down memory lane - Copenhagen .NET ...
Exploring .NET memory management - A trip down memory lane - Copenhagen .NET ...Exploring .NET memory management - A trip down memory lane - Copenhagen .NET ...
Exploring .NET memory management - A trip down memory lane - Copenhagen .NET ...Maarten Balliauw
 
ConFoo - Exploring .NET’s memory management – a trip down memory lane
ConFoo - Exploring .NET’s memory management – a trip down memory laneConFoo - Exploring .NET’s memory management – a trip down memory lane
ConFoo - Exploring .NET’s memory management – a trip down memory laneMaarten Balliauw
 
Unmanaged Parallelization via P/Invoke
Unmanaged Parallelization via P/InvokeUnmanaged Parallelization via P/Invoke
Unmanaged Parallelization via P/InvokeDmitri Nesteruk
 
JDD 2016 - Grzegorz Rozniecki - Java 8 What Could Possibly Go Wrong
JDD 2016 - Grzegorz Rozniecki - Java 8 What Could Possibly Go WrongJDD 2016 - Grzegorz Rozniecki - Java 8 What Could Possibly Go Wrong
JDD 2016 - Grzegorz Rozniecki - Java 8 What Could Possibly Go WrongPROIDEA
 
Java Garbage Collection, Monitoring, and Tuning
Java Garbage Collection, Monitoring, and TuningJava Garbage Collection, Monitoring, and Tuning
Java Garbage Collection, Monitoring, and TuningCarol McDonald
 
Quantifying the Performance of Garbage Collection vs. Explicit Memory Management
Quantifying the Performance of Garbage Collection vs. Explicit Memory ManagementQuantifying the Performance of Garbage Collection vs. Explicit Memory Management
Quantifying the Performance of Garbage Collection vs. Explicit Memory ManagementEmery Berger
 
Performance and predictability (1)
Performance and predictability (1)Performance and predictability (1)
Performance and predictability (1)RichardWarburton
 
Performance and Predictability - Richard Warburton
Performance and Predictability - Richard WarburtonPerformance and Predictability - Richard Warburton
Performance and Predictability - Richard WarburtonJAXLondon2014
 
Immutable Deployments with AWS CloudFormation and AWS Lambda
Immutable Deployments with AWS CloudFormation and AWS LambdaImmutable Deployments with AWS CloudFormation and AWS Lambda
Immutable Deployments with AWS CloudFormation and AWS LambdaAOE
 
Smash the Stack: Writing a Buffer Overflow Exploit (Win32)
Smash the Stack: Writing a Buffer Overflow Exploit (Win32)Smash the Stack: Writing a Buffer Overflow Exploit (Win32)
Smash the Stack: Writing a Buffer Overflow Exploit (Win32)Elvin Gentiles
 
NET Systems Programming Learned the Hard Way.pptx
NET Systems Programming Learned the Hard Way.pptxNET Systems Programming Learned the Hard Way.pptx
NET Systems Programming Learned the Hard Way.pptxpetabridge
 
GWT is Smarter Than You
GWT is Smarter Than YouGWT is Smarter Than You
GWT is Smarter Than YouRobert Cooper
 
Eclipse Memory Analyzer
Eclipse Memory AnalyzerEclipse Memory Analyzer
Eclipse Memory Analyzernayashkova
 
the productive programer: mechanics
the productive programer: mechanicsthe productive programer: mechanics
the productive programer: mechanicselliando dias
 
dotMemory 4 - What's inside?
dotMemory 4 - What's inside?dotMemory 4 - What's inside?
dotMemory 4 - What's inside?Maarten Balliauw
 
Best Practices for performance evaluation and diagnosis of Java Applications ...
Best Practices for performance evaluation and diagnosis of Java Applications ...Best Practices for performance evaluation and diagnosis of Java Applications ...
Best Practices for performance evaluation and diagnosis of Java Applications ...IndicThreads
 
Logging for Production Systems in The Container Era
Logging for Production Systems in The Container EraLogging for Production Systems in The Container Era
Logging for Production Systems in The Container EraSadayuki Furuhashi
 

Ähnlich wie DotNetFest - Let’s refresh our memory! Memory management in .NET (20)

Exploring .NET memory management - A trip down memory lane - Copenhagen .NET ...
Exploring .NET memory management - A trip down memory lane - Copenhagen .NET ...Exploring .NET memory management - A trip down memory lane - Copenhagen .NET ...
Exploring .NET memory management - A trip down memory lane - Copenhagen .NET ...
 
ConFoo - Exploring .NET’s memory management – a trip down memory lane
ConFoo - Exploring .NET’s memory management – a trip down memory laneConFoo - Exploring .NET’s memory management – a trip down memory lane
ConFoo - Exploring .NET’s memory management – a trip down memory lane
 
Unmanaged Parallelization via P/Invoke
Unmanaged Parallelization via P/InvokeUnmanaged Parallelization via P/Invoke
Unmanaged Parallelization via P/Invoke
 
JDD 2016 - Grzegorz Rozniecki - Java 8 What Could Possibly Go Wrong
JDD 2016 - Grzegorz Rozniecki - Java 8 What Could Possibly Go WrongJDD 2016 - Grzegorz Rozniecki - Java 8 What Could Possibly Go Wrong
JDD 2016 - Grzegorz Rozniecki - Java 8 What Could Possibly Go Wrong
 
Java Garbage Collection, Monitoring, and Tuning
Java Garbage Collection, Monitoring, and TuningJava Garbage Collection, Monitoring, and Tuning
Java Garbage Collection, Monitoring, and Tuning
 
Quantifying the Performance of Garbage Collection vs. Explicit Memory Management
Quantifying the Performance of Garbage Collection vs. Explicit Memory ManagementQuantifying the Performance of Garbage Collection vs. Explicit Memory Management
Quantifying the Performance of Garbage Collection vs. Explicit Memory Management
 
EnScript Workshop
EnScript WorkshopEnScript Workshop
EnScript Workshop
 
A Life of breakpoint
A Life of breakpointA Life of breakpoint
A Life of breakpoint
 
Performance and predictability (1)
Performance and predictability (1)Performance and predictability (1)
Performance and predictability (1)
 
Performance and Predictability - Richard Warburton
Performance and Predictability - Richard WarburtonPerformance and Predictability - Richard Warburton
Performance and Predictability - Richard Warburton
 
Immutable Deployments with AWS CloudFormation and AWS Lambda
Immutable Deployments with AWS CloudFormation and AWS LambdaImmutable Deployments with AWS CloudFormation and AWS Lambda
Immutable Deployments with AWS CloudFormation and AWS Lambda
 
Smash the Stack: Writing a Buffer Overflow Exploit (Win32)
Smash the Stack: Writing a Buffer Overflow Exploit (Win32)Smash the Stack: Writing a Buffer Overflow Exploit (Win32)
Smash the Stack: Writing a Buffer Overflow Exploit (Win32)
 
NET Systems Programming Learned the Hard Way.pptx
NET Systems Programming Learned the Hard Way.pptxNET Systems Programming Learned the Hard Way.pptx
NET Systems Programming Learned the Hard Way.pptx
 
Scope Stack Allocation
Scope Stack AllocationScope Stack Allocation
Scope Stack Allocation
 
GWT is Smarter Than You
GWT is Smarter Than YouGWT is Smarter Than You
GWT is Smarter Than You
 
Eclipse Memory Analyzer
Eclipse Memory AnalyzerEclipse Memory Analyzer
Eclipse Memory Analyzer
 
the productive programer: mechanics
the productive programer: mechanicsthe productive programer: mechanics
the productive programer: mechanics
 
dotMemory 4 - What's inside?
dotMemory 4 - What's inside?dotMemory 4 - What's inside?
dotMemory 4 - What's inside?
 
Best Practices for performance evaluation and diagnosis of Java Applications ...
Best Practices for performance evaluation and diagnosis of Java Applications ...Best Practices for performance evaluation and diagnosis of Java Applications ...
Best Practices for performance evaluation and diagnosis of Java Applications ...
 
Logging for Production Systems in The Container Era
Logging for Production Systems in The Container EraLogging for Production Systems in The Container Era
Logging for Production Systems in The Container Era
 

Mehr von Maarten Balliauw

Bringing nullability into existing code - dammit is not the answer.pptx
Bringing nullability into existing code - dammit is not the answer.pptxBringing nullability into existing code - dammit is not the answer.pptx
Bringing nullability into existing code - dammit is not the answer.pptxMaarten Balliauw
 
Nerd sniping myself into a rabbit hole... Streaming online audio to a Sonos s...
Nerd sniping myself into a rabbit hole... Streaming online audio to a Sonos s...Nerd sniping myself into a rabbit hole... Streaming online audio to a Sonos s...
Nerd sniping myself into a rabbit hole... Streaming online audio to a Sonos s...Maarten Balliauw
 
Building a friendly .NET SDK to connect to Space
Building a friendly .NET SDK to connect to SpaceBuilding a friendly .NET SDK to connect to Space
Building a friendly .NET SDK to connect to SpaceMaarten Balliauw
 
Microservices for building an IDE - The innards of JetBrains Rider - NDC Oslo...
Microservices for building an IDE - The innards of JetBrains Rider - NDC Oslo...Microservices for building an IDE - The innards of JetBrains Rider - NDC Oslo...
Microservices for building an IDE - The innards of JetBrains Rider - NDC Oslo...Maarten Balliauw
 
Indexing and searching NuGet.org with Azure Functions and Search - .NET fwday...
Indexing and searching NuGet.org with Azure Functions and Search - .NET fwday...Indexing and searching NuGet.org with Azure Functions and Search - .NET fwday...
Indexing and searching NuGet.org with Azure Functions and Search - .NET fwday...Maarten Balliauw
 
NDC Sydney 2019 - Microservices for building an IDE – The innards of JetBrain...
NDC Sydney 2019 - Microservices for building an IDE – The innards of JetBrain...NDC Sydney 2019 - Microservices for building an IDE – The innards of JetBrain...
NDC Sydney 2019 - Microservices for building an IDE – The innards of JetBrain...Maarten Balliauw
 
.NET Conf 2019 - Indexing and searching NuGet.org with Azure Functions and Se...
.NET Conf 2019 - Indexing and searching NuGet.org with Azure Functions and Se....NET Conf 2019 - Indexing and searching NuGet.org with Azure Functions and Se...
.NET Conf 2019 - Indexing and searching NuGet.org with Azure Functions and Se...Maarten Balliauw
 
CloudBurst 2019 - Indexing and searching NuGet.org with Azure Functions and S...
CloudBurst 2019 - Indexing and searching NuGet.org with Azure Functions and S...CloudBurst 2019 - Indexing and searching NuGet.org with Azure Functions and S...
CloudBurst 2019 - Indexing and searching NuGet.org with Azure Functions and S...Maarten Balliauw
 
NDC Oslo 2019 - Indexing and searching NuGet.org with Azure Functions and Search
NDC Oslo 2019 - Indexing and searching NuGet.org with Azure Functions and SearchNDC Oslo 2019 - Indexing and searching NuGet.org with Azure Functions and Search
NDC Oslo 2019 - Indexing and searching NuGet.org with Azure Functions and SearchMaarten Balliauw
 
Approaches for application request throttling - Cloud Developer Days Poland
Approaches for application request throttling - Cloud Developer Days PolandApproaches for application request throttling - Cloud Developer Days Poland
Approaches for application request throttling - Cloud Developer Days PolandMaarten Balliauw
 
Indexing and searching NuGet.org with Azure Functions and Search - Cloud Deve...
Indexing and searching NuGet.org with Azure Functions and Search - Cloud Deve...Indexing and searching NuGet.org with Azure Functions and Search - Cloud Deve...
Indexing and searching NuGet.org with Azure Functions and Search - Cloud Deve...Maarten Balliauw
 
Approaches for application request throttling - dotNetCologne
Approaches for application request throttling - dotNetCologneApproaches for application request throttling - dotNetCologne
Approaches for application request throttling - dotNetCologneMaarten Balliauw
 
ConFoo Montreal - Microservices for building an IDE - The innards of JetBrain...
ConFoo Montreal - Microservices for building an IDE - The innards of JetBrain...ConFoo Montreal - Microservices for building an IDE - The innards of JetBrain...
ConFoo Montreal - Microservices for building an IDE - The innards of JetBrain...Maarten Balliauw
 
ConFoo Montreal - Approaches for application request throttling
ConFoo Montreal - Approaches for application request throttlingConFoo Montreal - Approaches for application request throttling
ConFoo Montreal - Approaches for application request throttlingMaarten Balliauw
 
Microservices for building an IDE – The innards of JetBrains Rider - TechDays...
Microservices for building an IDE – The innards of JetBrains Rider - TechDays...Microservices for building an IDE – The innards of JetBrains Rider - TechDays...
Microservices for building an IDE – The innards of JetBrains Rider - TechDays...Maarten Balliauw
 
VISUG - Approaches for application request throttling
VISUG - Approaches for application request throttlingVISUG - Approaches for application request throttling
VISUG - Approaches for application request throttlingMaarten Balliauw
 
What is going on - Application diagnostics on Azure - TechDays Finland
What is going on - Application diagnostics on Azure - TechDays FinlandWhat is going on - Application diagnostics on Azure - TechDays Finland
What is going on - Application diagnostics on Azure - TechDays FinlandMaarten Balliauw
 
ConFoo - NuGet beyond Hello World
ConFoo - NuGet beyond Hello WorldConFoo - NuGet beyond Hello World
ConFoo - NuGet beyond Hello WorldMaarten Balliauw
 
Approaches to application request throttling
Approaches to application request throttlingApproaches to application request throttling
Approaches to application request throttlingMaarten Balliauw
 
NuGet beyond Hello World - DotNext Piter 2017
NuGet beyond Hello World - DotNext Piter 2017NuGet beyond Hello World - DotNext Piter 2017
NuGet beyond Hello World - DotNext Piter 2017Maarten Balliauw
 

Mehr von Maarten Balliauw (20)

Bringing nullability into existing code - dammit is not the answer.pptx
Bringing nullability into existing code - dammit is not the answer.pptxBringing nullability into existing code - dammit is not the answer.pptx
Bringing nullability into existing code - dammit is not the answer.pptx
 
Nerd sniping myself into a rabbit hole... Streaming online audio to a Sonos s...
Nerd sniping myself into a rabbit hole... Streaming online audio to a Sonos s...Nerd sniping myself into a rabbit hole... Streaming online audio to a Sonos s...
Nerd sniping myself into a rabbit hole... Streaming online audio to a Sonos s...
 
Building a friendly .NET SDK to connect to Space
Building a friendly .NET SDK to connect to SpaceBuilding a friendly .NET SDK to connect to Space
Building a friendly .NET SDK to connect to Space
 
Microservices for building an IDE - The innards of JetBrains Rider - NDC Oslo...
Microservices for building an IDE - The innards of JetBrains Rider - NDC Oslo...Microservices for building an IDE - The innards of JetBrains Rider - NDC Oslo...
Microservices for building an IDE - The innards of JetBrains Rider - NDC Oslo...
 
Indexing and searching NuGet.org with Azure Functions and Search - .NET fwday...
Indexing and searching NuGet.org with Azure Functions and Search - .NET fwday...Indexing and searching NuGet.org with Azure Functions and Search - .NET fwday...
Indexing and searching NuGet.org with Azure Functions and Search - .NET fwday...
 
NDC Sydney 2019 - Microservices for building an IDE – The innards of JetBrain...
NDC Sydney 2019 - Microservices for building an IDE – The innards of JetBrain...NDC Sydney 2019 - Microservices for building an IDE – The innards of JetBrain...
NDC Sydney 2019 - Microservices for building an IDE – The innards of JetBrain...
 
.NET Conf 2019 - Indexing and searching NuGet.org with Azure Functions and Se...
.NET Conf 2019 - Indexing and searching NuGet.org with Azure Functions and Se....NET Conf 2019 - Indexing and searching NuGet.org with Azure Functions and Se...
.NET Conf 2019 - Indexing and searching NuGet.org with Azure Functions and Se...
 
CloudBurst 2019 - Indexing and searching NuGet.org with Azure Functions and S...
CloudBurst 2019 - Indexing and searching NuGet.org with Azure Functions and S...CloudBurst 2019 - Indexing and searching NuGet.org with Azure Functions and S...
CloudBurst 2019 - Indexing and searching NuGet.org with Azure Functions and S...
 
NDC Oslo 2019 - Indexing and searching NuGet.org with Azure Functions and Search
NDC Oslo 2019 - Indexing and searching NuGet.org with Azure Functions and SearchNDC Oslo 2019 - Indexing and searching NuGet.org with Azure Functions and Search
NDC Oslo 2019 - Indexing and searching NuGet.org with Azure Functions and Search
 
Approaches for application request throttling - Cloud Developer Days Poland
Approaches for application request throttling - Cloud Developer Days PolandApproaches for application request throttling - Cloud Developer Days Poland
Approaches for application request throttling - Cloud Developer Days Poland
 
Indexing and searching NuGet.org with Azure Functions and Search - Cloud Deve...
Indexing and searching NuGet.org with Azure Functions and Search - Cloud Deve...Indexing and searching NuGet.org with Azure Functions and Search - Cloud Deve...
Indexing and searching NuGet.org with Azure Functions and Search - Cloud Deve...
 
Approaches for application request throttling - dotNetCologne
Approaches for application request throttling - dotNetCologneApproaches for application request throttling - dotNetCologne
Approaches for application request throttling - dotNetCologne
 
ConFoo Montreal - Microservices for building an IDE - The innards of JetBrain...
ConFoo Montreal - Microservices for building an IDE - The innards of JetBrain...ConFoo Montreal - Microservices for building an IDE - The innards of JetBrain...
ConFoo Montreal - Microservices for building an IDE - The innards of JetBrain...
 
ConFoo Montreal - Approaches for application request throttling
ConFoo Montreal - Approaches for application request throttlingConFoo Montreal - Approaches for application request throttling
ConFoo Montreal - Approaches for application request throttling
 
Microservices for building an IDE – The innards of JetBrains Rider - TechDays...
Microservices for building an IDE – The innards of JetBrains Rider - TechDays...Microservices for building an IDE – The innards of JetBrains Rider - TechDays...
Microservices for building an IDE – The innards of JetBrains Rider - TechDays...
 
VISUG - Approaches for application request throttling
VISUG - Approaches for application request throttlingVISUG - Approaches for application request throttling
VISUG - Approaches for application request throttling
 
What is going on - Application diagnostics on Azure - TechDays Finland
What is going on - Application diagnostics on Azure - TechDays FinlandWhat is going on - Application diagnostics on Azure - TechDays Finland
What is going on - Application diagnostics on Azure - TechDays Finland
 
ConFoo - NuGet beyond Hello World
ConFoo - NuGet beyond Hello WorldConFoo - NuGet beyond Hello World
ConFoo - NuGet beyond Hello World
 
Approaches to application request throttling
Approaches to application request throttlingApproaches to application request throttling
Approaches to application request throttling
 
NuGet beyond Hello World - DotNext Piter 2017
NuGet beyond Hello World - DotNext Piter 2017NuGet beyond Hello World - DotNext Piter 2017
NuGet beyond Hello World - DotNext Piter 2017
 

Último

UiPath Studio Web workshop Series - Day 3
UiPath Studio Web workshop Series - Day 3UiPath Studio Web workshop Series - Day 3
UiPath Studio Web workshop Series - Day 3DianaGray10
 
Automation Ops Series: Session 2 - Governance for UiPath projects
Automation Ops Series: Session 2 - Governance for UiPath projectsAutomation Ops Series: Session 2 - Governance for UiPath projects
Automation Ops Series: Session 2 - Governance for UiPath projectsDianaGray10
 
Scenario Library et REX Discover industry- and role- based scenarios
Scenario Library et REX Discover industry- and role- based scenariosScenario Library et REX Discover industry- and role- based scenarios
Scenario Library et REX Discover industry- and role- based scenariosErol GIRAUDY
 
Key Trends Shaping the Future of Infrastructure.pdf
Key Trends Shaping the Future of Infrastructure.pdfKey Trends Shaping the Future of Infrastructure.pdf
Key Trends Shaping the Future of Infrastructure.pdfCheryl Hung
 
Planetek Italia Srl - Corporate Profile Brochure
Planetek Italia Srl - Corporate Profile BrochurePlanetek Italia Srl - Corporate Profile Brochure
Planetek Italia Srl - Corporate Profile BrochurePlanetek Italia Srl
 
Emil Eifrem at GraphSummit Copenhagen 2024 - The Art of the Possible.pptx
Emil Eifrem at GraphSummit Copenhagen 2024 - The Art of the Possible.pptxEmil Eifrem at GraphSummit Copenhagen 2024 - The Art of the Possible.pptx
Emil Eifrem at GraphSummit Copenhagen 2024 - The Art of the Possible.pptxNeo4j
 
AI Workshops at Computers In Libraries 2024
AI Workshops at Computers In Libraries 2024AI Workshops at Computers In Libraries 2024
AI Workshops at Computers In Libraries 2024Brian Pichman
 
Design and Modeling for MySQL SCALE 21X Pasadena, CA Mar 2024
Design and Modeling for MySQL SCALE 21X Pasadena, CA Mar 2024Design and Modeling for MySQL SCALE 21X Pasadena, CA Mar 2024
Design and Modeling for MySQL SCALE 21X Pasadena, CA Mar 2024Alkin Tezuysal
 
The Zero-ETL Approach: Enhancing Data Agility and Insight
The Zero-ETL Approach: Enhancing Data Agility and InsightThe Zero-ETL Approach: Enhancing Data Agility and Insight
The Zero-ETL Approach: Enhancing Data Agility and InsightSafe Software
 
The New Cloud World Order Is FinOps (Slideshow)
The New Cloud World Order Is FinOps (Slideshow)The New Cloud World Order Is FinOps (Slideshow)
The New Cloud World Order Is FinOps (Slideshow)codyslingerland1
 
Introduction to RAG (Retrieval Augmented Generation) and its application
Introduction to RAG (Retrieval Augmented Generation) and its applicationIntroduction to RAG (Retrieval Augmented Generation) and its application
Introduction to RAG (Retrieval Augmented Generation) and its applicationKnoldus Inc.
 
Q4 2023 Quarterly Investor Presentation - FINAL - v1.pdf
Q4 2023 Quarterly Investor Presentation - FINAL - v1.pdfQ4 2023 Quarterly Investor Presentation - FINAL - v1.pdf
Q4 2023 Quarterly Investor Presentation - FINAL - v1.pdfTejal81
 
GraphSummit Copenhagen 2024 - Neo4j Vision and Roadmap.pptx
GraphSummit Copenhagen 2024 - Neo4j Vision and Roadmap.pptxGraphSummit Copenhagen 2024 - Neo4j Vision and Roadmap.pptx
GraphSummit Copenhagen 2024 - Neo4j Vision and Roadmap.pptxNeo4j
 
Patch notes explaining DISARM Version 1.4 update
Patch notes explaining DISARM Version 1.4 updatePatch notes explaining DISARM Version 1.4 update
Patch notes explaining DISARM Version 1.4 updateadam112203
 
UiPath Studio Web workshop series - Day 1
UiPath Studio Web workshop series  - Day 1UiPath Studio Web workshop series  - Day 1
UiPath Studio Web workshop series - Day 1DianaGray10
 
UiPath Studio Web workshop series - Day 4
UiPath Studio Web workshop series - Day 4UiPath Studio Web workshop series - Day 4
UiPath Studio Web workshop series - Day 4DianaGray10
 
Top 10 Squarespace Development Companies
Top 10 Squarespace Development CompaniesTop 10 Squarespace Development Companies
Top 10 Squarespace Development CompaniesTopCSSGallery
 
Introduction - IPLOOK NETWORKS CO., LTD.
Introduction - IPLOOK NETWORKS CO., LTD.Introduction - IPLOOK NETWORKS CO., LTD.
Introduction - IPLOOK NETWORKS CO., LTD.IPLOOK Networks
 
Stobox 4: Revolutionizing Investment in Real-World Assets Through Tokenization
Stobox 4: Revolutionizing Investment in Real-World Assets Through TokenizationStobox 4: Revolutionizing Investment in Real-World Assets Through Tokenization
Stobox 4: Revolutionizing Investment in Real-World Assets Through TokenizationStobox
 

Último (20)

UiPath Studio Web workshop Series - Day 3
UiPath Studio Web workshop Series - Day 3UiPath Studio Web workshop Series - Day 3
UiPath Studio Web workshop Series - Day 3
 
Automation Ops Series: Session 2 - Governance for UiPath projects
Automation Ops Series: Session 2 - Governance for UiPath projectsAutomation Ops Series: Session 2 - Governance for UiPath projects
Automation Ops Series: Session 2 - Governance for UiPath projects
 
SheDev 2024
SheDev 2024SheDev 2024
SheDev 2024
 
Scenario Library et REX Discover industry- and role- based scenarios
Scenario Library et REX Discover industry- and role- based scenariosScenario Library et REX Discover industry- and role- based scenarios
Scenario Library et REX Discover industry- and role- based scenarios
 
Key Trends Shaping the Future of Infrastructure.pdf
Key Trends Shaping the Future of Infrastructure.pdfKey Trends Shaping the Future of Infrastructure.pdf
Key Trends Shaping the Future of Infrastructure.pdf
 
Planetek Italia Srl - Corporate Profile Brochure
Planetek Italia Srl - Corporate Profile BrochurePlanetek Italia Srl - Corporate Profile Brochure
Planetek Italia Srl - Corporate Profile Brochure
 
Emil Eifrem at GraphSummit Copenhagen 2024 - The Art of the Possible.pptx
Emil Eifrem at GraphSummit Copenhagen 2024 - The Art of the Possible.pptxEmil Eifrem at GraphSummit Copenhagen 2024 - The Art of the Possible.pptx
Emil Eifrem at GraphSummit Copenhagen 2024 - The Art of the Possible.pptx
 
AI Workshops at Computers In Libraries 2024
AI Workshops at Computers In Libraries 2024AI Workshops at Computers In Libraries 2024
AI Workshops at Computers In Libraries 2024
 
Design and Modeling for MySQL SCALE 21X Pasadena, CA Mar 2024
Design and Modeling for MySQL SCALE 21X Pasadena, CA Mar 2024Design and Modeling for MySQL SCALE 21X Pasadena, CA Mar 2024
Design and Modeling for MySQL SCALE 21X Pasadena, CA Mar 2024
 
The Zero-ETL Approach: Enhancing Data Agility and Insight
The Zero-ETL Approach: Enhancing Data Agility and InsightThe Zero-ETL Approach: Enhancing Data Agility and Insight
The Zero-ETL Approach: Enhancing Data Agility and Insight
 
The New Cloud World Order Is FinOps (Slideshow)
The New Cloud World Order Is FinOps (Slideshow)The New Cloud World Order Is FinOps (Slideshow)
The New Cloud World Order Is FinOps (Slideshow)
 
Introduction to RAG (Retrieval Augmented Generation) and its application
Introduction to RAG (Retrieval Augmented Generation) and its applicationIntroduction to RAG (Retrieval Augmented Generation) and its application
Introduction to RAG (Retrieval Augmented Generation) and its application
 
Q4 2023 Quarterly Investor Presentation - FINAL - v1.pdf
Q4 2023 Quarterly Investor Presentation - FINAL - v1.pdfQ4 2023 Quarterly Investor Presentation - FINAL - v1.pdf
Q4 2023 Quarterly Investor Presentation - FINAL - v1.pdf
 
GraphSummit Copenhagen 2024 - Neo4j Vision and Roadmap.pptx
GraphSummit Copenhagen 2024 - Neo4j Vision and Roadmap.pptxGraphSummit Copenhagen 2024 - Neo4j Vision and Roadmap.pptx
GraphSummit Copenhagen 2024 - Neo4j Vision and Roadmap.pptx
 
Patch notes explaining DISARM Version 1.4 update
Patch notes explaining DISARM Version 1.4 updatePatch notes explaining DISARM Version 1.4 update
Patch notes explaining DISARM Version 1.4 update
 
UiPath Studio Web workshop series - Day 1
UiPath Studio Web workshop series  - Day 1UiPath Studio Web workshop series  - Day 1
UiPath Studio Web workshop series - Day 1
 
UiPath Studio Web workshop series - Day 4
UiPath Studio Web workshop series - Day 4UiPath Studio Web workshop series - Day 4
UiPath Studio Web workshop series - Day 4
 
Top 10 Squarespace Development Companies
Top 10 Squarespace Development CompaniesTop 10 Squarespace Development Companies
Top 10 Squarespace Development Companies
 
Introduction - IPLOOK NETWORKS CO., LTD.
Introduction - IPLOOK NETWORKS CO., LTD.Introduction - IPLOOK NETWORKS CO., LTD.
Introduction - IPLOOK NETWORKS CO., LTD.
 
Stobox 4: Revolutionizing Investment in Real-World Assets Through Tokenization
Stobox 4: Revolutionizing Investment in Real-World Assets Through TokenizationStobox 4: Revolutionizing Investment in Real-World Assets Through Tokenization
Stobox 4: Revolutionizing Investment in Real-World Assets Through Tokenization
 

DotNetFest - Let’s refresh our memory! Memory management in .NET

  • 1. Let’s refresh our memory! Memory management in .NET Maarten Balliauw @maartenballiauw
  • 2. .NET runtime Manages execution of programs Just-in-time compilation: Intermediate Language (IL) ->machine code Type safety Exception handling Security Thread management Memory management Garbage collection (GC)
  • 4. Memory management and GC “Virtually unlimited memory for our applications” Big chunk of memory pre-allocated Runtime manages allocation in that chunk Garbage Collector (GC) reclaims unused memory, making it available again
  • 5. .NET memory management 101 Memory allocation Objects allocated in “managed heap” (big chunk of memory) Allocating memory is fast, it’s just adding a pointer Some unmanaged memory is also consumed (not GC-ed) .NET CLR, Dynamic libraries, Graphics buffer, … Memory release or “Garbage Collection” (GC) Generations Large Object Heap
  • 6. .NET memory management 101 Memory allocation Memory release or “Garbage Collection” (GC) GC releases objects no longer in use by examining application roots GC builds a graph of all the objects that are reachable from these roots Object unreachable? Remove object, release memory, compact heap Takes time to scan all objects! Generations Large Object Heap
  • 7. .NET memory management 101 Memory allocation Memory release or “Garbage Collection” (GC) Generations Large Object Heap Generation 0 Generation 1 Generation 2 Short-lived objects (e.g. Local variables) In-between objects Long-lived objects (e.g. App’s main form)
  • 8. .NET memory management 101 Memory allocation Memory release or “Garbage Collection” (GC) Generations Large Object Heap (LOH) Special segment for large objects (>85KB) Collected only during full garbage collection Not compacted (by default) -> fragmentation! Fragmentation can cause OutOfMemoryException
  • 9. The .NET garbage collector Runs very often for gen0 Short-lived objects, few references, fast to clean Local variable Web request/response Higher generation Usually more references, slower to clean GC pauses the running application to do its thing Usually short, except when not… Background GC (enabled by default) Concurrent with application threads May still introduce short locks/pauses, usually just for one thread
  • 10. The .NET garbage collector When does it run? Vague… But usually: Out of memory condition – when the system fails to allocate or re-allocate memory After some significant allocation – if X memory is allocated since previous GC Failure of allocating some native resources – internal to .NET Profiler – when triggered from profiler API Forced – when calling methods on System.GC Application moves to background GC is not guaranteed to run http://blogs.msdn.com/b/oldnewthing/archive/2010/08/09/10047586.aspx http://blogs.msdn.com/b/abhinaba/archive/2008/04/29/when-does-the-net-compact-framework-garbage-collector-run.aspx
  • 11. Helping the GC, avoid pauses Optimize allocations (use struct when it makes sense, Span<T>, object pooling) Don’t allocate at all Make use of IDisposable / using statement Clean up references, giving the GC an easy job Weak references Allow the GC to collect these objects, no need for checks Finalizers Beware! Moved to finalizer queue -> always gen++
  • 14. When is memory allocated? Not for value types (int, bool, struct, decimal, enum, float, byte, long, …) Allocated on stack, not on heap Not managed by garbage collector For reference types When you new When you load data into a variable, object, property, ...
  • 15. Hidden allocations! Boxing! Put an int in a box Take an int out of a box Lambda’s/closures Allocate compiler-generated DisplayClass to capture state Params arrays And more! int i = 42; // boxing - wraps the value type in an "object box" // (allocating a System.Object) object o = i; // unboxing - unpacking the "object box" into an int again // (CPU effort to unwrap) int j = (int)o;
  • 16. How to find them? Past experience Intermediate Language (IL) Profiler “Heap allocations viewer” ReSharper Heap Allocations Viewer plugin Roslyn’s Heap Allocation Analyzer Don’t do premature optimization – measure!
  • 17. Hidden allocations DEMO https://github.com/maartenba/memory-demos ReSharper Heap Allocations Viewer plugin Roslyn’s Heap Allocation Analyzer
  • 18. Don’t optimize what should not be optimized.
  • 19. Measure! We know when allocations are done... ...but perhaps these don’t matter. Measure! How frequently are we allocating? How frequently are we collecting? What generation do we end up on? Are our allocations introducing pauses? www.jetbrains.com/dotmemory (and www.jetbrains.com/dottrace)
  • 21. Object pools / object re-use If it make sense, re-use objects Fewer allocations, fewer objects for the GC to scan Fewer memory traffic that can trigger a full GC Object pooling - object pool pattern Create a pool of objects that can be cleaned and re-used https://www.codeproject.com/articles/20848/c-object-pooling “Optimize ASP.NET Core” - https://github.com/aspnet/AspLabs/issues/3
  • 22. Garbage Collector & Allocations GC is optimized for high memory traffic in short-lived objects Use that knowledge! Don’t fear allocations! Don’t optimize what should not be optimized… GC is the concept that makes .NET / C# tick – use it! Know when allocations happen GC is awesome Gen2 collection that stop the world not so much… Measure!
  • 24. Strings are objects .NET tries to make them look like a value type, but they are a reference type Read-only collection of char Length property A bunch of operator overloading Allocated on the managed heap var a = new string('-', 25); var b = a.Substring(5); var c = httpClient.GetStringAsync("http://blog.maartenballiauw.be");
  • 25. String literals Are all strings on the heap? Are all strings duplicated? var a = "Hello, World!"; var b = "Hello, World!"; Console.WriteLine(a == b); Console.WriteLine(Object.ReferenceEquals(a, b)); Prints true twice. So “Hello World” only in memory once?
  • 27. String literals in #US Compile-time optimization Store literals only once in PE header metadata stream ECMA-335 standard, section II.24.2.4 Reference literals (IL: ldstr) var a = Console.ReadLine(); var b = Console.ReadLine(); Console.WriteLine(a == b); Console.WriteLine(Object.ReferenceEquals(a, b));
  • 28. String duplicates Any .NET application has them (System.Globalization duplicates quite a few) Are they bad? .NET GC is fast for short-lived objects, so meh. Don’t waste memory with string duplicates on gen2 (but: it’s okay to have strings there)
  • 29. String interning Store (and read) strings from the intern pool Simply call String.Intern when “allocating” or reading the string Scans intern pool and returns reference var url = "http://blog.maartenballiauw.be"; var stringList = new List<string>(); for (int i = 0; i < 1000000; i++) { stringList.Add(string.Intern(url + "/")); }
  • 30. String interning caveats Why are not all strings interned by default? CPU vs. memory Not on the heap but on intern pool No GC on intern pool – all strings in memory for AppDomain lifetime! Rule of thumb Lot of long-lived, few unique -> interning good Lot of long-lived, many unique -> no benefit, memory growth Lot of short-lived -> trust the GC Measure!
  • 31. Exploring the heap for fun and profit
  • 32. How would you do it... Build a managed type system, store in memory, CPU/memory friendly Probably: Store type info (what’s in there, what’s the offset of fieldN, …) Store field data (just data) Store method pointers (“who you gonna call?”) Inheritance information
  • 33. Stuff on the Stack
  • 34. Stuff on the Managed Heap (scroll down for more...)
  • 35. .NET memory is like a database Pointer to an “instance” Instance Pointer to Runtime Type Information (RTTI) Field values (which can be pointers in turn) RunTime Type Information Interface addresses Instance method addresses Static method addresses …
  • 36. Theory is nice... Microsoft.Diagnostics.Runtime (ClrMD) “ClrMD is a set of advanced APIs for programmatically inspecting a crash dump of a .NET program much in the same way that the SOS Debugging Extensions (SOS) do. This allows you to write automated crash analysis for your applications as well as automate many common debugger tasks. In addition to reading crash dumps ClrMD also allows supports attaching to live processes.” “LINQ-to-heap” Maarten’s definition
  • 38. But... Why? Programmatic insight into memory space of a running project Unit test critical paths and assert behavior (did we clean up what we expected?) Capture memory issues in running applications Other options in this space dotMemory Unit (JetBrains) Benchmark.NET
  • 40. Conclusion Garbage Collector (GC) optimized for high memory traffic + short-lived objects Don’t fear allocations! But beware of gen2 “stop the world” String interning when lot of long-lived, few unique Don’t optimize what should not be optimized… Measure! Using a profiler/memory analysis tool ClrMD to automate inspections dotMemory Unit, Benchmark.NET, … to profile unit tests Blog series: https://blog.maartenballiauw.be
  • 41. .NET Internals: stack memory management Nikolay Balakin 16:05 – Track 2

Hinweis der Redaktion

  1. https://pixabay.com/en/memory-computer-component-pcb-1761599/
  2. https://pixabay.com/en/tires-used-tires-pfu-garbage-1846674/
  3. Application roots: Typically, these are global and static object pointers, local variables, and CPU registers.
  4. Application roots: Typically, these are global and static object pointers, local variables, and CPU registers.
  5. Application roots: Typically, these are global and static object pointers, local variables, and CPU registers.
  6. Open TripDownMemoryLane.sln Show WeakReferenceDemo (demo “1-1”) Explain weak reference allows GC to collect reference Show Cache object – has weak references to data, we expect these to probably be cleaned up by GC Attach profiler, run demo “1-1”, snapshot, see 20 instances of WeakReference<Data> Snapshot again, compare – see WeakReference<Data> has been regenerated a couple of times Show DisposeObjectsDemo (demo “1-2”) Explain first demo does not dispose and relies on GC + finalizers. This will mean our object remains in memory for two GC cycles! Explain dispose does clean them up and requires only one cycle In SampleDisposable, explain GC.SuppressFinalize -> tell the GC no finalizer queue work is needed here!
  7. Open TripDownMemoryLane.sln Show Demo02_Random Open IL viewer tool window, show what happens in IL for each code sample Explain IL viewer + hovering statements to see what they do BoxingRing() – show boxing and unboxing statements in IL, explain they consume CPU and allocate an object ParamsArray() – the call to ParamsArrayImpl() actually allocates a new string array! CPU + memory AverageWithinBounds() – temporary class is created to capture state of all variables, then passed around IL_0000: newobj instance void TripDownMemoryLane.Demo02.Demo02_Random/'<>c__DisplayClass3_0'::.ctor() Lambdas() – same thing, temporary class to capture state in the loop IL_001f: newobj instance void Allocatey.Talk.Demo02_Random/'<>c__DisplayClass4_0'::.ctor() Show Demo02_ValidateArgumentsDemo – this one is fun! Explain what we want to do: build a guard function – check a condition, show error First one is the easy one, but it allocates a string and runs string.Format Second one is better – does not allocate the string! But does allocate a function and a state capture... Third one – allocates an array (params) Fourth one – no allocations, yay! Using overloads... Show heap allocations viewer!
  8. Open TripDownMemoryLane.sln Show BeersDemoUnoptimized (demo “3-1” and “3-2”) Explain we’re building an application that shows all beers in the world and their ratings Stored in beers.json (show document) with beer name, brewery, number of votes For a view in our application, read this file into a multi-dimensional dictionary that contains breweries, beers, and their rating Show BeerLoader and note the dictionary format Show LoadBeersInsane and explain this is BAD BAD BAD because of the high memory usage Show LoadBeersUnoptimized, explain what it does, optimized against the insane version as we’re streaming over our file Load beers a number of times Inspect snapshots GC is very visible Most memory in gen2 (we keep our beers around) Compare two snapshots: high traffic on dictionary items (Lots of string allocations - JSON.NET) Show LoadBeersOptimized, explain what it does, re-using dictionary and updating items as we read the JSON Load beers a number of times Inspect snapshots GC is almost invisible Less allocations happening Compare two snapshots: almost no traffic Less work for GC, less pauses! Measure and make it look good!
  9. There is an old adage in IT that says “don’t do premature optimization”. In other words: maybe some allocations are okay to have, as the GC will take care of cleaning them up anyway. While some do not agree with this, I believe in the middle ground. The garbage collector is optimized for high memory traffic in short-lived objects, and I think it’s okay to make use of what the .NET runtime has to offer us here. If it’s in a critical path of a production application, fewer allocations are better, but we can’t write software with zero allocations - it’s what our high-level programming language uses to make our developer life easier. It’s not okay to have objects go to gen2 and stay there when in fact they should be gone from memory. Learn where allocations happen, using any of the above methods, and profile your production applications frequently to see if there are large objects in higher generations of the heap that don’t belong there.
  10. Will print “true” twice.
  11. Open our demo application in dotPeek Explain PE headers Show #US table Open StringAllocationDemo class. Jump to IL code, show ldstr statement for strings that are in #US table
  12. Code = trick question, what if we enter same value twice? String equals, reference not equals!
  13. How many strings are stored
  14. How many strings are stored
  15. Open ClrMD.sln Explain: two projects, one target application, one running ClrMD to analyze what we have Open ClrMD.Explorer.Program, show attaching ClrMD Get CLR version – gets info about the current CLR version Get runtime – gets info about the actual runtime hosting our app Show DumpClrInfo – get info, stress DAC data access components location – defines the runtime structures, used by ClrMD and VS Debugger etc to explore runtime while debugging/profiling/... Explore DumpHeapObjects, stress the heap structure Loop object addresses - foreach (var objectAddress in generation) Get type of object at address - var type = heap.GetObjectType(objectAddress.Ptr); Use type info to get value - type.GetValue(objectAddress.Ptr) Explore type autocomplete – structure to get enum, method addresses, ...