jvm-hotspot

As we know, some JIT allows reordering for object initialization, for example, someRef = new SomeObject(); can be decomposed into below steps: objRef = allocate space for SomeObject; //step1 call constructor of SomeObject; //step2 someRef = objRef; //step3 JIT compiler may reorder it as below: objRef = allocate space for SomeObject; //step1 someRef = objRef; //step3 call constructor of SomeObject; //step2 namely, step2 and step3 can be reordered by JIT compiler. Even though this is theoretically valid reordering, I was unable to reproduce it with Hotspot(jdk1.7) under x86 platform. So, Is

This question already has an answer here: Eligibility for escape analysis / stack allocation with Java 7 3 answers Since somewhere around Java 6, the Hotspot JVM can do escape analysis and allocate non-escaping objects on the stack instead of on the garbage collected heap. This results in a speedup of the generated code and reduces pressure on the garbage collector. What are the rules for when Hotspot is able to stack allocate objects? In other words when can I rely on it to do stack allocation? edit : This question is a duplicate, but (IMO) the answer below is a better answer than what is

If anyone can give me brief information about the advantages and disadvantages of the two JVM since they all depend on the Standard JVM Specification. haylem JRockit was originally developed by Appeal and BEA Systems before being acquired by Oracle to run server software. 1 It was meant to be optimized for large applications requiring long running tasks, a lot of memory and a scalable environment, pushing optimizations for these scenarios even further than the Sun HotSpot JVM in server-mode (see also: Real differences between "java -server" and "java -client"? ). Since the acquisition of Sun

I was benchmarking some code, and I could not get it to run as fast as with java.math.BigInteger , even when using the exact same algorithm. So I copied java.math.BigInteger source into my own package and tried this: //import java.math.BigInteger; public class MultiplyTest { public static void main(String[] args) { Random r = new Random(1); long tm = 0, count = 0,result=0; for (int i = 0; i < 400000; i++) { int s1 = 400, s2 = 400; BigInteger a = new BigInteger(s1 * 8, r), b = new BigInteger(s2 * 8, r); long tm1 = System.nanoTime(); BigInteger c = a.multiply(b); if (i > 100000) { tm += System

Suppose we have 3 methods: method 2 is called from method 1, method 3 is called from method 2. Methods 2 and 3 are of size 30 bytecodes each. Also, suppose for definiteness method 2 is always called from method 1 exactly once, and method 3 is always called from method 2 exaclty once. If method 2 is inlined first, method 3 will be called from the body of method 1 directly, and could be inlined in its turn. If method 3 is inlined into method 2 first, the size of the latter will become about 60 bytecodes, and it couldn't be inlined, because default MaxInlineSize threshold is 35 bytecodes. In