jit

问题 I would like to learn what native instructions Java's JIT compiler generates when it loads a class file. Is there any way of knowing it? I am working in Linux on a 586 processor. And I am using Sun's JDK 1.6 update 21. Is there any tool that I can use to find out what I am looking for? 回答1: You probably need -XX:+PrintOptoAssembly , but you'd need a debug build of the JVM. The links to the binary distributions seem not to be available any longer, so you might have to build it from source:

问题 I'm trying to produce some "Hello World" size C# code snippet that would incur JIT inlining. So far I have this: class Program { static void Main(string[] args) { Console.WriteLine( GetAssembly().FullName ); Console.ReadLine(); } static Assembly GetAssembly() { return System.Reflection.Assembly.GetCallingAssembly(); } } which I compile as "Release"-"Any CPU" and "Run without debugging" from Visual Studio. It displays the name of my sample program assembly so clearly GetAssembly() is not

问题 It takes 15 minutes or more for POI to initialize its first workbook in Java 8 on Windows 10, in a Tomcat 8 instance. Based on interrupting the process in the debugger and looking at the stack, it is spending the time in the classloader, driven by xbeans. Edit This has the feel of a classloader issue because when I implemented the workaround for the POI library (below), other classes started expressing the same issue. Edit The stack trace looks most similar to this bug: https://bugs.java.com

问题 I am implementing a front-end for a JIT compiler using LLVM. I started by following the Kaleidoscope example in the LLVM tutorial. I know how to generate and JIT LLVM IR using the LLVM C++ API. I also know how to call the JITed function, using the "getPointerToFunction" method of llvm::ExecutionEngine. getPointerToFunction returns a void* which I must then cast to the correct function type. For example, in my compiler I have unit test that looks like the following: void* compiled_func =

问题 I am trying to optimize my application for for it to perform well right after it is started. At the moment, its distribution contains 304 binaries (including external dependencies) totaling 57 megabytes. It is a WPF application doing mostly database access, without any significant calculations. I discovered that the Debug configuration offers way better (~5 times gain) times for most operations, as they are performed for the first time during the lifetime of the application's process. For

问题 Since so there are so many JIT implementation out there, every JIT emits native code. Then why hasn't someone made a tool like JIT2EXE, to save the native code to a native executable? 回答1: The question is kind of vague as you have not clearly specified what language you are talking about, in my area of .NET, the .NET executables are pre-jitted at runtime in order to speed up the loading times. The code can be generated to native code by a process known as NGEN which takes the .NET IL code and

问题 I have a BIG application that I'm trying to optimize. to do so, I'm profiling / benchmarking small elements of it by running them millions of times in a loop, and checking their processing time. obviously Hotspot's JIT is kicking in, and I can actually see when that happens. I like it, I can clearly see things going much faster after the "warm up" period. however, after reaching the fastest execution speed and keeping it for some time, I can see that the speed is then reduced to a less

问题 I'm working on an application where I'd like to dynamically generate code for a numerical calculation (for performance). Doing this calculation as a data driven operation is too slow. To describe my requirements, consider this class: class Simulation { Dictionary<string, double> nodes; double t, dt; private void ProcessOneSample() { t += dt; // Expensive operation that computes the state of nodes at the current t. } public void Process(int N, IDictionary<string, double[]> Input, IDictionary

问题 Does class file format provide support for final keyword in case of using it with variables? Or does it just deduce the effective finality of a variable from code and JIT compiler perform optimization based on it? Here, in class file format documentation, they mentioned about final keyword, but only in case of using it with final block and final class . There is nothing about final variables . 回答1: No, there is no such information encoded in class file. You may easily verify this by compiling

问题 I'm comparing performance of MethodHandle::invoke and direct static method invokation. Here is the static method: public class IntSum { public static int sum(int a, int b){ return a + b; } } And here is my benchmark: @State(Scope.Benchmark) public class MyBenchmark { public int first; public int second; public final MethodHandle mhh; @Benchmark @OutputTimeUnit(TimeUnit.NANOSECONDS) @BenchmarkMode(Mode.AverageTime) public int directMethodCall() { return IntSum.sum(first, second); } @Benchmark