我目前正在做一些最后的测量优化,主要是为了娱乐和学习,并发现了一些让我有几个问题的东西。
首先,问题:
Expression<...>
版本比最小的DynamicMethod版本运行得更快?这是一个简短而完整的程序。在我的系统上,输出是:
DynamicMethod: 887 ms
Lambda: 1878 ms
Method: 1969 ms
Expression: 681 ms
我希望lambda和方法调用具有更高的值,但DynamicMethod版本一直慢约30-50%(变化可能是由于Windows和其他程序)。有人知道原因吗?
以下是该计划:
using System;
using System.Linq.Expressions;
using System.Reflection.Emit;
using System.Diagnostics;
namespace Sandbox
{
public class Program
{
public static void Main(String[] args)
{
DynamicMethod method = new DynamicMethod("TestMethod",
typeof(Int32), new Type[] { typeof(Int32), typeof(Int32) });
var il = method.GetILGenerator();
il.Emit(OpCodes.Ldarg_0);
il.Emit(OpCodes.Ldarg_1);
il.Emit(OpCodes.Add);
il.Emit(OpCodes.Ret);
Func<Int32, Int32, Int32> f1 =
(Func<Int32, Int32, Int32>)method.CreateDelegate(
typeof(Func<Int32, Int32, Int32>));
Func<Int32, Int32, Int32> f2 = (Int32 a, Int32 b) => a + b;
Func<Int32, Int32, Int32> f3 = Sum;
Expression<Func<Int32, Int32, Int32>> f4x = (a, b) => a + b;
Func<Int32, Int32, Int32> f4 = f4x.Compile();
for (Int32 pass = 1; pass <= 2; pass++)
{
// Pass 1 just runs all the code without writing out anything
// to avoid JIT overhead influencing the results
Time(f1, "DynamicMethod", pass);
Time(f2, "Lambda", pass);
Time(f3, "Method", pass);
Time(f4, "Expression", pass);
}
}
private static void Time(Func<Int32, Int32, Int32> fn,
String name, Int32 pass)
{
Stopwatch sw = new Stopwatch();
sw.Start();
for (Int32 index = 0; index <= 100000000; index++)
{
Int32 result = fn(index, 1);
}
sw.Stop();
if (pass == 2)
Debug.WriteLine(name + ": " + sw.ElapsedMilliseconds + " ms");
}
private static Int32 Sum(Int32 a, Int32 b)
{
return a + b;
}
}
}
答案 0 :(得分:54)
通过DynamicMethod
创建的方法经历了两次thunks,而通过Expression<>
创建的方法不会通过任何方法。
这是它的工作原理。这是在fn(0, 1)
方法中调用Time
的调用序列(为了便于调试,我将参数硬编码为0和1):
00cc032c 6a01 push 1 // 1 argument
00cc032e 8bcf mov ecx,edi
00cc0330 33d2 xor edx,edx // 0 argument
00cc0332 8b410c mov eax,dword ptr [ecx+0Ch]
00cc0335 8b4904 mov ecx,dword ptr [ecx+4]
00cc0338 ffd0 call eax // 1 arg on stack, two in edx, ecx
对于我调查的第一次调用DynamicMethod
,call eax
行如此出现:
00cc0338 ffd0 call eax {003c2084}
0:000> !u 003c2084
Unmanaged code
003c2084 51 push ecx
003c2085 8bca mov ecx,edx
003c2087 8b542408 mov edx,dword ptr [esp+8]
003c208b 8b442404 mov eax,dword ptr [esp+4]
003c208f 89442408 mov dword ptr [esp+8],eax
003c2093 58 pop eax
003c2094 83c404 add esp,4
003c2097 83c010 add eax,10h
003c209a ff20 jmp dword ptr [eax]
这似乎是在进行一些堆栈调整以重新排列参数。我推测这是由于使用隐含的'this'参数的代表与不使用隐式'this'参数的代理之间的区别。
最后的跳跃就这样解决了:
003c209a ff20 jmp dword ptr [eax] ds:0023:012f7edc=0098c098
0098c098 e963403500 jmp 00ce0100
0098c098的其余代码看起来像是一个JIT thunk,它的开始在JIT之后用jmp
重写。只有在这次跳转之后我们才能获得真正的代码:
0:000> !u eip
Normal JIT generated code
DynamicClass.TestMethod(Int32, Int32)
Begin 00ce0100, size 5
>>> 00ce0100 03ca add ecx,edx
00ce0102 8bc1 mov eax,ecx
00ce0104 c3 ret
通过Expression<>
创建的方法的调用顺序是不同的 - 它缺少堆栈混合代码。这是从第一次跳转到eax
:
00cc0338 ffd0 call eax {00ce00a8}
0:000> !u eip
Normal JIT generated code
DynamicClass.lambda_method(System.Runtime.CompilerServices.ExecutionScope, Int32, Int32)
Begin 00ce00a8, size b
>>> 00ce00a8 8b442404 mov eax,dword ptr [esp+4]
00ce00ac 03d0 add edx,eax
00ce00ae 8bc2 mov eax,edx
00ce00b0 c20400 ret 4
现在,事情是怎么发生的?
我不知道LINQ如何强制JIT,但我确实知道如何自己强制使用JIT - 至少调用一次该函数。更新:我找到了强制JIT的另一种方法:使用restrictedSkipVisibility
argumetn到构造函数并传递true
。所以,这里的修改代码通过使用隐式'this'参数来消除堆栈混合,并使用备用构造函数进行预编译,以便绑定地址是真实地址,而不是thunk:
using System;
using System.Linq.Expressions;
using System.Reflection.Emit;
using System.Diagnostics;
namespace Sandbox
{
public class Program
{
public static void Main(String[] args)
{
DynamicMethod method = new DynamicMethod("TestMethod",
typeof(Int32), new Type[] { typeof(object), typeof(Int32),
typeof(Int32) }, true);
var il = method.GetILGenerator();
il.Emit(OpCodes.Ldarg_1);
il.Emit(OpCodes.Ldarg_2);
il.Emit(OpCodes.Add);
il.Emit(OpCodes.Ret);
Func<Int32, Int32, Int32> f1 =
(Func<Int32, Int32, Int32>)method.CreateDelegate(
typeof(Func<Int32, Int32, Int32>), null);
Func<Int32, Int32, Int32> f2 = (Int32 a, Int32 b) => a + b;
Func<Int32, Int32, Int32> f3 = Sum;
Expression<Func<Int32, Int32, Int32>> f4x = (a, b) => a + b;
Func<Int32, Int32, Int32> f4 = f4x.Compile();
for (Int32 pass = 1; pass <= 2; pass++)
{
// Pass 1 just runs all the code without writing out anything
// to avoid JIT overhead influencing the results
Time(f1, "DynamicMethod", pass);
Time(f2, "Lambda", pass);
Time(f3, "Method", pass);
Time(f4, "Expression", pass);
}
}
private static void Time(Func<Int32, Int32, Int32> fn,
String name, Int32 pass)
{
Stopwatch sw = new Stopwatch();
sw.Start();
for (Int32 index = 0; index <= 100000000; index++)
{
Int32 result = fn(index, 1);
}
sw.Stop();
if (pass == 2)
Console.WriteLine(name + ": " + sw.ElapsedMilliseconds + " ms");
}
private static Int32 Sum(Int32 a, Int32 b)
{
return a + b;
}
}
}
这是我系统上的运行时间:
DynamicMethod: 312 ms
Lambda: 417 ms
Method: 417 ms
Expression: 312 ms
最新添加:
我尝试在我的新系统上运行此代码,这是运行安装了.NET 4 beta 2的Windows 7 x64的Core i7 920(mscoree.dll版本4.0.30902),结果很好,可变。
csc 3.5, /platform:x86, runtime v2.0.50727 (via .config)
Run #1
DynamicMethod: 214 ms
Lambda: 571 ms
Method: 570 ms
Expression: 249 ms
Run #2
DynamicMethod: 463 ms
Lambda: 392 ms
Method: 392 ms
Expression: 463 ms
Run #3
DynamicMethod: 463 ms
Lambda: 570 ms
Method: 570 ms
Expression: 463 ms
也许这是Intel SpeedStep影响结果,或者可能是Turbo Boost。无论如何,这很烦人。
csc 3.5, /platform:x64, runtime v2.0.50727 (via .config)
DynamicMethod: 428 ms
Lambda: 392 ms
Method: 392 ms
Expression: 428 ms
csc 3.5, /platform:x64, runtime v4
DynamicMethod: 428 ms
Lambda: 356 ms
Method: 356 ms
Expression: 428 ms
csc 4, /platform:x64, runtime v4
DynamicMethod: 428 ms
Lambda: 356 ms
Method: 356 ms
Expression: 428 ms
csc 4, /platform:x86, runtime v4
DynamicMethod: 463 ms
Lambda: 570 ms
Method: 570 ms
Expression: 463 ms
csc 3.5, /platform:x86, runtime v4
DynamicMethod: 214 ms
Lambda: 570 ms
Method: 571 ms
Expression: 249 ms
这些结果中的许多都是计时事故,无论是什么导致C#3.5 /运行时v2.0场景中的随机加速。我必须重新启动,看看SpeedStep或Turbo Boost是否对这些影响负责。