jvm-hotspot

Is there any utility or script, either using java or native code, to see list of all strings present in String Pool in JDK 8 HotSpot JVM, without having lot of performance impact on JVM? Alternatively can I have a listener hooked up whenever a new string is being added into JVM? Thanks, Harish You can easily make such yourself utility using HotSpot Serviceability Agent which is included in JDK by default. import sun.jvm.hotspot.memory.SystemDictionary; import sun.jvm.hotspot.oops.InstanceKlass; import sun.jvm.hotspot.oops.OopField; import sun.jvm.hotspot.runtime.VM; import sun.jvm.hotspot

I'm currently evaluating the G1 garbage collector and how it performs for our application. Looking at the gc-log, I noticed a lot of collections have very long "Scan RS" phases: 7968.869: [GC pause (mixed), 10.27831700 secs] [Parallel Time: 10080.8 ms] (...) [Scan RS (ms): 4030.4 4034.1 4032.0 4032.0 Avg: 4032.1, Min: 4030.4, Max: 4034.1, Diff: 3.7] [Object Copy (ms): 6038.5 6033.3 6036.7 6037.1 Avg: 6036.4, Min: 6033.3, Max: 6038.5, Diff: 5.2] (...) [Eden: 19680M(19680M)->0B(20512M) Survivors: 2688M->2624M Heap: 75331M(111904M)->51633M(115744M)] [Times: user=40.49 sys=0.02, real=10.28 secs]

I am using the following JVM parameters to start-up a JVM with the hostpot debugger. -Xdebug -Xrunjdwp:server=y,transport=dt_socket,address=0 Note that I am assigning port zero, so that the JVM asks the OS for an ephemeral port. This is critical for my use-case, to make sure the JVM will not fail to start-up due to contention for some pre-defined port. As a result my JVM starts-up, and the following log entry is outputted to stdout : Listening for transport dt_socket at address: XXXX I would like to find some way to identify the debug port from inside or outside of the JVM, so it would be

I would like to get the equivalent of the ouput of jmap -histo programmatically, from inside the monitored application. I see triggering a binary heap dump is possible through the HotSpot diagnostic bean, but I can't see how to get the histogram data. Is it possible ? It may be not the best example/code, but have a look at this (I think it's only working on Hotspot JVMs) 来源： https://stackoverflow.com/questions/9417038/how-to-get-jmap-histogram-programmatically

I am getting an error message from the Java compiler that I don't understand. I've tested my code on OSX 10.6, 10.9, and Ubuntu 14.04, with both Java 6 and 7. When I run with the Eclipse debugger or from the interpreter (using -Xint option), everything runs fine. Otherwise, I get the following messages: Java 1.6: Invalid memory access of location 0x8 rip=0x1024e9660 Java 1.7: # # A fatal error has been detected by the Java Runtime Environment: # # SIGSEGV (0xb) at pc=0x000000010f7a8262, pid=20344, tid=18179 # # JRE version: Java(TM) SE Runtime Environment (7.0_60-b19) (build 1.7.0_60-b19) #

This question already has an answer here: Print All JVM Flags 2 answers Besides official documentation I have found only this post . But it is quite old and incomplete (only -XX options available). For example, I couldn't find -XX:AutoBoxCacheMax option in none of them. Where the complete list can be found if it exists? You can use java -XX:+UnlockDiagnosticVMOptions -XX:+PrintFlagsFinal -version to print all options and their defaults. If you have a debug build you can use this command to print comments for the various options as well: java -XX:+UnlockDiagnosticVMOptions -XX:

CAUTION: it is not a duplicate, please read topic сarefully https://stackoverflow.com/users/3448419/apangin quote: The real question is why the code sometimes works when it should not. The issue reproduces even without lambdas. This makes me think there might be a JVM bug. In the comments of https://stackoverflow.com/a/53709217/2674303 I tried to find out reasons why code behaves differently from one start to another and participants of that discussion made me piece of of advice to create a separated topic. Let's consider following source code: public class Test { static { System.out.println(

Java 8 reserves 1G for Metaspace just after it starts. It means that minimum metaspace size is 1G. But I set up MetaspaceSize to 300m and MaxMetaspaceSize to 400m. Why Java reserves more then I allow? Java Version $ java -version java version "1.8.0_45" Java(TM) SE Runtime Environment (build 1.8.0_45-b14) Java HotSpot(TM) 64-Bit Server VM (build 25.45-b02, mixed mode) VM Flags $ jcmd 21689 VM.flags 21689: -XX:CICompilerCount=3 -XX:ConcGCThreads=1 -XX:G1HeapRegionSize=1048576 -XX:InitialHeapSize=62914560 -XX:+ManagementServer -XX:MarkStackSize=4194304 -XX:MaxHeapSize=1006632960 -XX

I switched to CMS collector for my application and throughput of application decreased by half. From GC logs, I see a high frequency of minor GCs happening (aroung 10 per second ). I have allocated a heap size of 4G . The JVM be default is using very small size for young gen (less than 40MB ). I want to try out CMS via increasing the size of young gen. Can you point me to right JVM parameter for this. I tried -XX:NewRatio but JVM ignored this parameter and there was no change in young gen sizes My java version is java version "1.6.0_14" How did you set -XX:NewRatio , and on which JVM version?