jvm-hotspot

问题 I'm trying to run and debug the utilies from sun.jvm.hotspot.tools and sun.jvm.hotspot.utilities (like JMap.java) in order to understand better what is going on. Unfortunately I get stuck very early with the following error message and don't even get to debug a lot: Attaching to process ID 5144, please wait... Error attaching to process: Timed out while attempting to connect to debug server (please start SwDbgSrv.exe) It seems like for whatever reason the tools are trying to connect to a

问题 I'm trying to run and debug the utilies from sun.jvm.hotspot.tools and sun.jvm.hotspot.utilities (like JMap.java) in order to understand better what is going on. Unfortunately I get stuck very early with the following error message and don't even get to debug a lot: Attaching to process ID 5144, please wait... Error attaching to process: Timed out while attempting to connect to debug server (please start SwDbgSrv.exe) It seems like for whatever reason the tools are trying to connect to a

问题 As we know some people say java JIT is faster then C++. I had some idea to utilize JIT and remove some instructions at runtime code. Here is sample code i tried: /** * Created by kadirbasol on 4/6/14. */ public class RemoveJump { public final boolean test; private static RemoveJump instance = new RemoveJump(); public static final RemoveJump getInstance() { return instance; } private RemoveJump() { //set the test on the constructor once and //remove this if statement forever from testLoop test

问题 I have to evaluate how difficult it would be to extract some object (e.g. java.security.PrivateKey ) from memory of a running java program. I'm not very into this low level memory stuff, so I started out with small C programs and familiarized myself with gdb , /proc/<pid>/maps , /proc/<pid>/mem and a script that dumps all the memory areas. However, things change when switching to java. Memory is allocated and managed very differently with java thanks to garbage collection. In C programs I'd

问题 Objective I'm doing dynamic bytecode instrumentation using a JVMTI agent. I have to instrument those methods which are "hot", that is, the methods which invoke JIT compiler. To do so I listen to a CompiledLoadEvent and inside its call back function, call RetransformClasses . This in turn invokes ClassFileLoadHook on the class containing "hot" function and actual instrumentation begins. Problem Premises Currently I'm instrumenting my class to spawn some threads. I also listen to thread starts

问题 I want to add a java agent to process ID of the already running java application. Is there any way doing that using command line, something like java -jar java agent.jar process_id or if i can edit the hotspot JVM start up script directly to add the java agent there itself, but how can i edit the hotspot JVM start up script. I am using UNIX. 回答1: If you are working with the sun JVM you can use the dynamic attach agent. http://docs.oracle.com/javase/7/docs/technotes/guides/attach/index.html 来源

问题 Guys when the JVM Crashes it writes an Error Log hs_err_pid.log. I want to find out what caused the JVM to crash ? How to understand these Logs, is it documented anywhere on how this Log is arranged. I tried to search on the Net but to no avail :-( Pointing out to relevant URL's will be appreciated. Thanks. 回答1: Unless you are calling native code (JNI), nothing in your code should ever make JVM crash; so the stack trace information in that log file is probably not meant to be very useful to

问题 "Hotspot can remove bounds checking in Java." Can any one explain this please? Actually im analysing the differences between C++ and Java. It is not a homework and im analysing on my own interest. 回答1: After googling "hotspot bounds checking", a Paper with the Title "Array Bounds Check Elimination for the Java HotSpot™ Client Compiler" shows up (as the first result) and gives us some insight: Abstract: Whenever an array element is accessed, Java virtual machines execute a compare instruction

问题 Whilst running test code from this question and fiddling with the JVM's thread stack size, I found that results were not necessarily repeatable: there were values of stack size for which the program would sometimes throw java.lang.StackOverflowError , but sometimes not . My question is: "What is causing the variation in stack space consumption?" Also, can an interrupt's stack be put on this program's main thread? Will results be similarly non-deterministic for other JVM implementations and/or

问题 I need to create a wifi hotspot and a DHCP server in Windows 7-8 with Java. I'm developing a software that could be for the user less intrusive and simple that i could. For the first part of my work, I thought to use netsh to create the hosted network and to set static the ip. my current code is this: String[] command = { "cmd", }; Process p = Runtime.getRuntime().exec(command); new Thread(new SyncPipe(p.getErrorStream(), System.err)).start(); new Thread(new SyncPipe(p.getInputStream(),