jvm

问题 As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, visit the help center for guidance. Closed 8 years ago . I'm after a book to learn about the internals of the Java virtual machine. I found this thread but it is two years old now. Are there

问题 This question already has answers here : Running jmap getting Unable to open socket file (4 answers) Closed 3 years ago . I am running the command: jstack 1234 > threadDump.tdump On an PID of a Java process. I keep getting the following message: Unable to open socket file: target process not responding or HotSpot VM not loaded The -F option can be used when the target process is not responding I am not asking just how to solve, but I want to understand why I am getting this message, since I

问题 This question already has answers here : Running jmap getting Unable to open socket file (4 answers) Closed 3 years ago . I am running the command: jstack 1234 > threadDump.tdump On an PID of a Java process. I keep getting the following message: Unable to open socket file: target process not responding or HotSpot VM not loaded The -F option can be used when the target process is not responding I am not asking just how to solve, but I want to understand why I am getting this message, since I

问题 I am struggling to hunt down the "Full GC" on our production JVM. Every day at around midnight the STW occurs without apparent reason, quite deadly for 10-11 sec. Here is the gc log: Java HotSpot(TM) 64-Bit Server VM (25.131-b11) for windows-amd64 JRE (1.8.0_131-b11), built on Mar 15 2017 01:23:53 by "java_re" with MS VC++ 10.0 (VS2010) Memory: 4k page, physical 16584284k(13074876k free), swap 23137624k(18439472k free) CommandLine flags: -XX:GCLogFileSize=1024000 -XX:InitialHeapSize

问题 I have 2 interfaces, and 2 return types. interface interfaceA { Publisher<String> doSomething(); } interface interfaceB extends interfaceA { Flow<String> doSomething(); } interface Publisher<T>{} class Flow<T> implements Publisher<T>{} So at runtime, I can see 2 methods of interfaceB.class.getMethods() public default my.package.Publisher my.package.interfaceB.doSomething() public abstract my.package.Flow my.package.interfaceB.doSomething() Regarding the first one, it is Synthetic. (method

问题 The application is basically a Servlet on top of Apaches Tomcat 8 and crashes every 3 to n days. The most interesting part is, that the last 3 crashes happened at 1.30 PM + 3 to 4 seconds. Every other crash happens at 15, 30, 45 or the full hour. The same application worked for months on Windows 7 with Java 7 something. I found this report so I checked the available space at /tmp and I have plenty of space here. However, the next time I ran the VM with: -XX:-UsePerfData -XX:

问题 MemoryMXBean.getHeapMemoryUsage() I have a jvm process that ran with -Xms512m -Xmx512m, and below show the MemoryMXBean.getHeapMemoryUsage() of this process: init = 512M used = 105M comitted = 491M max = 491M Why max is 491M(I expect it to be 512M)? MemoryMXBean.getNonHeapMemoryUsage() MemoryMXBean.getNonHeapMemoryUsage() of this process: init = 2M used = 25M comitted = 25M max = 0M What does the non-heap(who uses it) means? What kind of memory will be count into this non-heap? I only know

问题 MemoryMXBean.getHeapMemoryUsage() I have a jvm process that ran with -Xms512m -Xmx512m, and below show the MemoryMXBean.getHeapMemoryUsage() of this process: init = 512M used = 105M comitted = 491M max = 491M Why max is 491M(I expect it to be 512M)? MemoryMXBean.getNonHeapMemoryUsage() MemoryMXBean.getNonHeapMemoryUsage() of this process: init = 2M used = 25M comitted = 25M max = 0M What does the non-heap(who uses it) means? What kind of memory will be count into this non-heap? I only know

问题 I know that the new , dup , invokespecial and astore bytecode pattern will invoke the instance initializer method <init> when someone instance a Java class from the Java language point of view, but i never figure out who invoke the special <clinit> method and when does this happen? My guess is that <clinit> is invoked before <init> method. Can any body give me some information to prove it? Is this documented in the JVM Specification or Java Language Specification? 回答1: JVM spec §2.9. Special

问题 I understand that the sun.* packages are not part of the official Java API. However, I need to use some functionality similar to what Perf offers: specifically Basic JVM Metrics (Heap, Threads, PermGen, etc), JvmStat counters to GC, etc. Does anybody know a wrapper library around Perf and PerfInstrumentation which comes with a good documentation. I need to use it as an API so e.g. the VisualVM's Tracer plugin is not good enough. Anybody has a comment on that? 回答1: There are wrapper around JVM