Starting with the premise that "Performance is a Feature", Matt Warren will show you how to measure, what to measure and how to get the best performance from your .NET code.
We will look at real-world examples from the Roslyn code-base and StackOverflow (the product), including how the .NET Garbage Collector needs to be tamed!
The presentation covers:
Why we should care about performance
Pitfalls to avoid when measuring performance
How the .NET Garbage Collector can hurt performance
Real-world performance lessons from open-source code
The webinar recording can be found here: http://www.postsharp.net/blog/post/webinar-recording-performance-is-a-feature
9. Why?
“The most amazing achievement of
the computer software industry is its
continuing cancellation of the steady
and staggering gains made by the
computer hardware industry.”
- Henry Petroski
10. Why?
“We should forget about small efficiencies,
say about 97% of the time: premature
optimization is the root of all evil. Yet we
should not pass up our opportunities in
that critical 3%.“
- Donald Knuth
11. Why?
“We should forget about small efficiencies,
say about 97% of the time: premature
optimization is the root of all evil. Yet we
should not pass up our opportunities in
that critical 3%.“
- Donald Knuth
12. Never give up your
performance accidentally
Rico Mariani,
Performance Architect @
Microsoft
23. How?
“The simple act of putting a render time in the upper right hand corner of every
page we serve forced us to fix all our performance regressions and omissions.”
30. using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;
static Uri @object = new Uri("http://google.com/search");
[Benchmark(Baseline = true)]
public string RegularPropertyCall()
{
return @object.Host;
}
[Benchmark]
public object Reflection()
{
Type @class = @object.GetType();
PropertyInfo property =
@class.GetProperty(propertyName, bindingFlags);
return property.GetValue(@object);
}
static void Main(string[] args)
{
var summary = BenchmarkRunner.Run<Program>();
}
31. Watch the webinar recording here:
http://www.postsharp.net/blog/pos
t/webinar-recording-performance-
is-a-feature
32. Compared to one second
• Millisecond – ms
–thousandth (0.001 or 1/1000)
• Microsecond - μs
–millionth (0.000001 or 1/1,000,000)
• Nanosecond - ns
–billionth (0.000000001 or 1/1,000,000,000)
33. BenchmarkDotNet
BenchmarkDotNet=v0.9.4.0
OS=Microsoft Windows NT 6.1.7601 Service Pack 1
Processor=Intel(R) Core(TM) i7-4800MQ CPU @ 2.70GHz, ProcessorCount=8
HostCLR=MS.NET 4.0.30319.42000, Arch=32-bit RELEASE
JitModules=clrjit-v4.6.100.0
Type=Program Mode=Throughput
Method | Median | StdDev | Scaled |
--------------------- |------------ |----------- |------- |
RegularPropertyCall |
Reflection |
35. [Params(1, 2, 3, 4, 5, 10, 100, 1000)]
public int Loops;
[Benchmark]
public string StringConcat()
{
string result = string.Empty;
for (int i = 0; i < Loops; ++i)
result = string.Concat(result, i.ToString());
return result;
}
[Benchmark]
public string StringBuilder()
{
StringBuilder sb = new StringBuilder(string.Empty);
for (int i = 0; i < Loops; ++i)
sb.Append(i.ToString());
return sb.ToString();
}
https://github.com/dotnet/roslyn/issues/5388
42. Stack Overflow Performance Lessons
Use static classes
Don’t be afraid to write your own tools
Dapper, Jil, MiniProfiler,
Intimately know your platform - CLR
43.
44. Roslyn Performance Lessons 1
public class Logger
{
public static void WriteLine(string s) { /*...*/ }
}
public class Logger
{
public void Log(int id, int size)
{
var s = string.Format("{0}:{1}", id, size);
Logger.WriteLine(s);
}
}
Essential Truths Everyone Should Know about Performance in a Large Managed Codebase
http://channel9.msdn.com/Events/TechEd/NorthAmerica/2013/DEV-B333
45. Roslyn Performance Lessons 1
public class Logger
{
public static void WriteLine(string s) { /*...*/ }
}
public class BoxingExample
{
public void Log(int id, int size)
{
var s = string.Format("{0}:{1}",
id.ToString(), size.ToString());
Logger.WriteLine(s);
}
}
https://github.com/dotnet/roslyn/pull/415
AVOID BOXING
46. Roslyn Performance Lessons 2
class Symbol {
public string Name { get; private set; }
/*...*/
}
class Compiler {
private List<Symbol> symbols;
public Symbol FindMatchingSymbol(string name)
{
return symbols.FirstOrDefault(s => s.Name == name);
}
}
47. Roslyn Performance Lessons 2
class Symbol {
public string Name { get; private set; }
/*...*/
}
class Compiler {
private List<Symbol> symbols;
public Symbol FindMatchingSymbol(string name)
{
foreach (Symbol s in symbols)
{
if (s.Name == name)
return s;
}
return null;
}
}
DON’T USE LINQ
49. Roslyn Performance Lessons 3
public class Example
{
// Constructs a name like "Foo<T1, T2, T3>"
public string GenerateFullTypeName(string name, int arity)
{
StringBuilder sb = new StringBuilder();
sb.Append(name);
if (arity != 0)
{
sb.Append("<");
for (int i = 1; i < arity; i++)
{
sb.Append('T'); sb.Append(i.ToString());
}
sb.Append('T'); sb.Append(arity.ToString());
}
return sb.ToString();
}
}
50. Roslyn Performance Lessons 3
public class Example
{
// Constructs a name like "Foo<T1, T2, T3>"
public string GenerateFullTypeName(string name, int arity)
{
StringBuilder sb = new AcquireBuilder();
sb.Append(name);
if (arity != 0)
{
sb.Append("<");
for (int i = 1; i < arity; i++)
{
sb.Append('T'); sb.Append(i.ToString());
}
sb.Append('T'); sb.Append(arity.ToString());
}
return GetStringAndReleaseBuilder(sb);
}
}
OBJECT POOLING
53. Watch the webinar recording here:
http://www.postsharp.net/blog/pos
t/webinar-recording-performance-
is-a-feature
Notes de l'éditeur
Who has: - any perf requirements - perf requirements with numbers! - any perf tests - perf test that are run continuously
I’m joined by Tony from PostSharp, ask questions on GoToWebinar question box (will be answered at the end)
Who has: - any perf requirements - perf requirements with numbers! - any perf tests - perf test that are run continuously
Front-end
- YSlow, Google PageSpeed, CDN & caching
- "High Performance Web Sites" by Steve Sounder
Database & caching
- Learn to use SQL Profiler
- Redis or similar
- MiniProfiler
.NET (server-side) <- This is what we are looking at
Mechanical Sympathy
- Anything by Martin Thompson
- Disruptor and Disruptor.NET
- CPU caches (L1, L2, etc)
- memory access patterns
Save money when running in the cloud (Zeeshan anecdote) - Scale-up rather than just scale-out- Save power on mobile devices (also bad perf more obvious on constrained device)- To users bad performance looks like you're website isn't working! - PerfBytes podcast, "News Of The Damned", a.k.a "which UK ticketing site has crashed this week"!- Bad performance might be losing you customers, before you even got them!!
- Even internal L.O.B apps - What could Dave in accounting do with an extra 50 minutes per week (10 min per/day) - Maybe the really slow accounting app is the reason for him quitting and going to work for your main competitor!!
Henry Petroski (February 6, 1942) is an American engineer specializing in failure analysis. A professor both of civil engineering and history at Duke University, he is also a prolific author.
To Engineer Is Human: The Role of Failure in Successful Design
To know the critical 3%, we have to measure,
Except Donal Knuth, who never write slow code and
if he did, he would know which bit was slow!
To know the critical 3%, we have to measure,
Except Donal Knuth, who never write slow code and
if he did, he would know which bit was slow!
Thanks him for making Visual Studio faster
He helped fix it after adding WPF made it SLOW!!!!
Should be roughly 10-15 mins in by now, if not hurry up!!!!
Normal distribution
Things like height, weight, DOESN’T apply to everything!!
Average is just less than 2, i.e. 1.995 or something like that
But > 99% of people in the UK have 2 legs (more than the average)
This is a histogram,
Real-world example
Web page response times
Why are there 2 groups of histograms bar?
- fast = cached data
- slow = hitting the database
Pause, for Tony to ask a question here (about next slide, ‘real-world’ example)
Unit tests are meant to be fast, and they only test 1 thing
In dev you don’t always have a full set of data
You don’t test for long periods of time
Smaller setup
Michelle Bustamante talk about logging, don’t just need to measure things,
Need to log the data AND be able to get at it!!
You’ll probably guess wrong!!
Consider adding performance unit tests,
Noda-Time does this, can graph performance over time, see if it’s regressed!!
MiniProfiler
Turn this on in Development and if possible in Production
Glimpse is an alternative
Runs on .NET,
Puts everything in 1 place, Web Server & Database
Summary metrics up front
Can drill-down into detailed metrics, including executed SQL, page load times, etc
Make sure you are really measuring what you think you are measuring!!
Question about profiler, fixing the most expensive things first, 80/20 rule?
Make sure you are really measuring what you think you are measuring!!
Question: how does it compare to other tools
Nbench
Xunit Performance
https://github.com/dotnet/roslyn/issues/5388
Implement string concatenation in loops via manipulating a StringBuilder instead of emitting String.Concat()
WON’T be implemented by the compiler
Question: when doing code review, should performance be taken into consideration
Both StackOverflow and Roslyn affected by this!!!!!
In the .NET Framework 4.5, there is background server garbage collection (before .NET 4.5 was Workstation only)
So until .NET 4.5, Server GC was STOP-THE-WORLD
Process Explorer
From Sysinternals
PerfView is a stand-alone utility, to help you debug CPU and memory problems
Light-weight and non-intrusive, can be used to on production apps with minimal impact
Uses ETW (Event Tracing for Windows), designed to be v. fast!!!!
They were able to graph these results & equate them to Garbage Collector pauses!!!
They had good logging and measurements in place,
They measured and found that all of these were on the HOT PATH
https://github.com/dotnet/roslyn/pull/415 Avoid unnecessary boxing with String.Concat
Able to implement this optimization for types which are immutable, pure, and not affected by other code. Notably:
- bool
- char (and this was one of the motivating types for this optimization)
- IntPtr
- UIntPtr
Due to side-effects of calling ToString() implementations that rely on the current culture (i.e. it culture can be changed mid-way through and you’ll see different behaviour)