Игорь Фесенко "Direction of C# as a High-Performance Language"

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Direction of C# as a High-
Performance Language
Igor Fesenko
SoftServe Inc.
@ky7m

Who am I?
• Leading software development
projects
• Passionate about high burst/HPC
systems
• Design cloud ready software ...

“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 l...

Problem?
@ky7m #dotnet
#fwdays

.NET
@ky7m #dotnet
#fwdays

.NE
T
Problem?
@ky7m #dotnet
#fwdays

• Garbage collection
• Allocation-rich APIs and patterns
Why Not C#?
@ky7m #dotnet
#fwdays

Memory Allocations Everywhere

Code Generation
@ky7m #dotnet
#fwdays

• Just-In-Time (JIT) - CoreCLR
• fast compile times
• simple
• decent code quality
• Ahead-Of-Time (AOT) - CoreRT
• best c...

Code Generation
JIT
AOT
AOT
@ky7m #dotnet
#fwdays

• Inlining
• Flowgraph and loop analysis
• Range analysis
• SIMD and vectorization
• Dead code elimination
• …
/optimize+
...

Inlining
• New stack frame
• Save return
address
• Save registers
• Call
• Restore context
@ky7m #dotnet
#fwdays

Inlining
int tmp = a; a = b; b = tmp;
void Swap<T>(ref T a, ref T b)
{
T tmp = a; a = b; b = tmp;
}
@ky7m #dotnet
#fwdays

Allocation
• Allocates up to 2
objects
• lambda
• captured stack
frame @ky7m #dotnet
#fwdays

Stop the world!
@ky7m #dotnet
#fwdays

• Generational, compacting garbage collector
• Large Object Heap (LOH) manually only
• Manual “low pause” regions
• LowLat...

• Language Feature Status
• C# 7.0
• Binary Literals
• Digit Separators
• Local Functions
• Type switch
• Ref Returns
• Tu...

Who wants to be a Millionaire?

C# 6.0 Quiz
@ky7m #dotnet
#fwdays

A. All options are correct
What is the correct C# syntax to declare
the getter-only auto-property ?
Opt. 1 - public int Pr...

A. All options are correct
D. I’m Java developer
What is the correct C# syntax to declare
the getter-only auto-property ?
...

A. All options are correct
D. I’m Java developer
What is the correct C# syntax to declare
the getter-only auto-property ?
...

Local Functions
@ky7m #dotnet
#fwdays

Local Functions
List<T> items,
values
values,
• Value Type
to build
closure
@ky7m #dotnet
#fwdays

Ref Returns
@ky7m #dotnet
#fwdays

Ref Returns
ref
ref
ref ref
place = 9;
WriteLine(array[4]); // prints 9
@ky7m #dotnet
#fwdays

Tuples
• New Tuples are value
types
@ky7m #dotnet
#fwdays

• Struct type
• Not replace Task, but help to
• drastically reduce the number of allocations
• method inlining
ValueTask<T...

The hardest problem in computer science is
fighting the urge to solve a different, more
interesting problem than the one a...

• Exposes implementation details
• Code Complexity
• Obscures Logic
• Missing Static Checks
• More Exception Handlers
• Se...

• Available on Nuget -
https://www.nuget.org/packages/FastMember
• Open-source -
https://github.com/mgravell/fast-member/
...

FastMember Example Usage
var
string // smth known at runtime
while /* some loop of data */
// obj could be static or DLR
v...

FastMember and SqlBulkCopy
var new
var
@ky7m #dotnet
#fwdays

• Nuget -
https://www.nuget.org/packages/System.Runtime.Co
mpilerServices.Unsafe/
• Low-level functionality for manipulati...

Unsafe class api
public static class Unsafe
// all methods are public static unsafe
void
void void value
int
object where ...

With Unsafe you’re more Safe
var 10
var ref //void*
var int // int
@ky7m #dotnet
#fwdays

• One Really Big Query Expression (60-line query)
• A lot of LINQ To * (what you want)
LINQ is fantastic feature of C#!
@k...

Even R# helps…
@ky7m #dotnet
#fwdays

• Hidden allocations
• Possible multiple enumeration
• Easy to write a non-optimal query
LINQ downsides
@ky7m #dotnet
#fwd...

• Nuget -
https://www.nuget.org/packages/LinqOptimizer.CSharp/
• Works at run-time
• Requires AsQueryExpr().Run() to LINQ ...

• https://github.com/antiufo/roslyn-linq-rewrite
• Works at compile time (build step)
• No code changes
• No allocations f...

• https://github.com/dotnet/corefxlab/tree/master/src
/System.Slices
• Span is a simple struct that gives you uniform acce...

Make subslices without allocations
byte stackalloc byte 256
var new byte 256
char new char ’ ' 'N' 'E' 'T'
char new char
c...

• Nuget -
https://www.nuget.org/packages/System.Buffers/
• ArrayPool
• resource pool that enables reusing instances of T[]...

• Get your own instance
• ArrayPool<T>.Shared (Thread safe)
• NativeBufferPool<byte>.SharedByteBufferPool (Thread
safe)
• ...

• Heap allocation viewer
Heap Allocations Viewer R# plugin
Clr Heap Allocation Analyzer VS extension
• Roslyn analyzers
ht...

• C# delivers productivity and safety, good
performance from JIT to AOT and everything in
between
• A lot of features are ...

• https://github.com/dotnet/corefx
• https://github.com/dotnet/coreclr
• https://github.com/dotnet/corefxlab
• https://git...

Questions
@ky7m | ifesenko.com |
ifesen@softserveinc.com

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