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Direction of C# as a High-Performance LanguageIgor FesenkoSoftServe Inc.
@ky7m
Who am I?
• Leading software development
projects
• Passionate about high burst/HPC
systems
• Design cloud ready software solutions
• SoftServe .NET Community leader
• Conference speaker and trainer
• More… go to ifesenko.com
“Performance of my code is awesome.”
Developer
“…premature optimization is the root of all evil…”
Donald Knuth
• Productivity and ease of use
• Built-in safety
• Powerful async and concurrency models
• Mature ecosystem of tools and libraries
Why C#?
@ky7m #dotnet
#fwdays
Problem?
@ky7m #dotnet
#fwdays
.NET
@ky7m #dotnet
#fwdays
.NET
Problem?
@ky7m #dotnet
#fwdays
• Garbage collection
• Allocation-rich APIs and patterns
Why Not C#?
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Memory Allocations Everywhere
Code Generation
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• Just-In-Time (JIT) - CoreCLR
• fast compile times
• simple
• decent code quality
• Ahead-Of-Time (AOT) - CoreRT
• best code quality
• slower compile times
• complex deployment model
• Hybrid [Future]
• let the system adaptively recompile
Code Generation
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#fwdays
Code Generation
JITAOT
AOT
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• Inlining
• Flowgraph and loop analysis
• Range analysis
• SIMD and vectorization
• Dead code elimination
• …
/optimize+
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#fwdays
Inlining
• New stack frame
• Save return address
• Save registers
• Call
• Restore context
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Inlining
int tmp = a; a = b; b = tmp;
void Swap<T>(ref T a, ref T b)
{
T tmp = a; a = b; b = tmp;
}
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#fwdays
Allocation
• Allocates up to 2 objects
• lambda
• captured stack frame
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Stop the world!
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• Generational, compacting garbage collector
• Large Object Heap (LOH) manually only
• Manual “low pause” regions
• LowLatency
• TryStartNoGCRegion
• Parallel collector for server workloads
• Server mode
• .NET 4.5 concurrent + parallel in harmony
Garbage Collection
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• Language Feature Status
• C# 7.0
• Binary Literals
• Digit Separators
• Local Functions
• Type switch
• Ref Returns
• Tuples
• Out var
• ValueTask
• …
C# 7 Features
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Who wants to be a Millionaire?
C# 6.0 Quiz
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A. All options are correct
What is the correct C# syntax to declare
the getter-only auto-property ?
Opt. 1 - public int Property1 => 42;
Opt. 2 - public int Property2 { get => 42; }
Opt. 3 - public int Property3 { get { return 42; }
B. Options 1 and 3
C. Option 3 D. I’m Java developer
A. All options are correct
D. I’m Java developer
What is the correct C# syntax to declare
the getter-only auto-property ?
Opt. 1 - public int Property1 => 42;
Opt. 2 - public int Property2 { get => 42; }
Opt. 3 - public int Property3 { get { return 42; }
A. All options are correct
D. I’m Java developer
What is the correct C# syntax to declare
the getter-only auto-property ?
Opt. 1 - public int Property1 => 42;
Opt. 2 - public int Property2 { get => 42; }
Opt. 3 - public int Property3 { get { return 42; }
Local Functions
@ky7m #dotnet
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Local Functions
List<T> items,
values
values,
• Value Type to build closure
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Ref Returns
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Ref Returnsref
ref
ref ref
place = 9;
WriteLine(array[4]); // prints 9
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Tuples
• New Tuples are value types
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• Struct type
• Not replace Task, but help to
• drastically reduce the number of allocations
• method inlining
ValueTask<T>
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#fwdays
The hardest problem in computer science is fighting the urge to solve a different, more interesting problem than the one at hand.
Nick Lockwood
• Exposes implementation details
• Code Complexity
• Obscures Logic
• Missing Static Checks
• More Exception Handlers
• Security
• Performance
Problems with Reflection
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• Available on Nuget -https://www.nuget.org/packages/FastMember
• Open-source -https://github.com/mgravell/fast-member/
• Uses ILGenerator and SiteCall power
FastMember
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FastMember Example Usagevar
string // smth known at runtime while /* some loop of data */
// obj could be static or DLR
var
string // smth known at runtime
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FastMember and SqlBulkCopyvar newvar
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• Nuget -https://www.nuget.org/packages/System.Runtime.CompilerServices.Unsafe/
• Low-level functionality for manipulating pointers
• Whole code is single IL file
System.Runtime.CompilerServices.Unsafe
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Unsafe class apipublic static class Unsafe
// all methods are public static unsafe
void
void void value
int
object where class
void ref value
ref void
void InitBlock void byte uint
void CopyBlock void void uint
ref void
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With Unsafe you’re more Safevar 10
var ref //void*
var int // int
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• One Really Big Query Expression (60-line query)
• A lot of LINQ To * (what you want)
LINQ is fantastic feature of C#!
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#fwdays
Even R# helps…
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• Hidden allocations
• Possible multiple enumeration
• Easy to write a non-optimal query
LINQ downsides
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• Nuget -https://www.nuget.org/packages/LinqOptimizer.CSharp/
• Works at run-time
• Requires AsQueryExpr().Run() to LINQ methods
• Optimizes Parallel LINQ
• Specialized strategies and algorithms
LinqOptimizer
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• https://github.com/antiufo/roslyn-linq-rewrite
• Works at compile time (build step)
• No code changes
• No allocations for Expression<> trees and enumerator boxing
• Parallel LINQ is not supported
RoslynLinqRewrite
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• https://github.com/dotnet/corefxlab/tree/master/src/System.Slices
• Span is a simple struct that gives you uniform access to any kind of contiguous memory
• It provides a uniform API for working with:
• Unmanaged memory buffers
• Arrays and subarrays
• Strings and substrings
• It’s fully type-safe and memory-safe.
• Almost no overhead.
Span (Slice)
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Make subslices without allocationsbyte stackalloc byte 256
var new byte 256
char new char ’ ' 'N' 'E' 'T'char new char
char0 4
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• Nuget -https://www.nuget.org/packages/System.Buffers/
• ArrayPool
• resource pool that enables reusing instances of T[]
• managed memory
• NativeBufferPool (experimental, under corefxlab)
• Unmanaged memory
• pool of Slice<T>
System.Buffers
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• Get your own instance • ArrayPool<T>.Shared (Thread safe)
• NativeBufferPool<byte>.SharedByteBufferPool (Thread safe)
• ArrayPool<T>.Create(int maxArrayLength, ..)
• Rent
• Specify the min size
• Bigger can be returned, don’t rely on .Length
• Finally { Return }
• Alternative - Microsoft.IO.RecyclableMemoryStream
• Provide pooling for .NET MemoryStream objects
• Limited usage
How to work with Pools
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• Heap allocation viewerHeap Allocations Viewer R# pluginClr Heap Allocation Analyzer VS extension
• Roslyn analyzershttps://github.com/dotnet/roslyn-analyzershttps://github.com/Wintellect/Wintellect.Analyzershttps://github.com/DotNetAnalyzers/StyleCopAnalyzers
• Annotations[StackOnly] - Microsoft.CodeAnalysis.StackOnlyTypes[NoAlloc] ensures a method doesn’t allocate [MustNotCopy] ensures a struct isn’t copied [Scoped] ensures a value doesn’t escape the callee... and more ...
Essential tools in your toolbox
@ky7m #dotnet
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• C# delivers productivity and safety, good performance from JIT to AOT and everything in between
• A lot of features are “free”
• Structs can improve memory performance
• Less GC pressure
• Better memory locality
• Less overall space usage
• Beware of copying large structs, “ref returns”
• New features in next rev of C# and .NET: ValueTask, ValueTuple, others
• Use power of Roslyn
Summary
• https://github.com/dotnet/corefx
• https://github.com/dotnet/coreclr
• https://github.com/dotnet/corefxlab
• https://github.com/dotnet/roslyn
• https://github.com/dotnet/corert
• https://github.com/dotnet/coreclr/blob/master/Documentation/botr/readytorun-overview.md
Links
