I have been using the following flags in my application using Java 8:-
1) PrintFLSStatistics=1
2) +PrintPromotionFailure
3) -XX:+PrintGCDateStamps
4) -XX:+PrintGCDetails
I have been moving the application to use Java 11 instead of Java 8. It seems these flags are either deprecated or not supported in Java 11. Please tell the alternatives of these flags in Java 11.
Thanks for your time,
In Java 11, you have to use -Xlog instead. For example: java -Xlog:gc\*::time -jar my.jar will log something like
[2020-02-19T18:32:50.107-0300] Heap region size: 1M
[2020-02-19T18:32:50.119-0300] Using G1
[2020-02-19T18:32:50.119-0300] Heap address: 0x000000070a200000, size: 3934 MB, Compressed Oops mode: Zero based, Oop shift amount: 3
-Xlog is the general logging configuration option for logging in the HotSpot JVM. It's a tag-based system where gc is one of the tags. To
get more information about what a GC is doing, you can configure
logging to print any message that has the gc tag and any other tag.
The command line option for this is -Xlog:gc*.
See:
https://docs.oracle.com/javase/9/tools/java.htm#GUID-BE93ABDC-999C-4CB5-A88B-1994AAAC74D5
https://docs.oracle.com/en/java/javase/11/gctuning/garbage-collector-implementation.html#GUID-A24775AB-16A3-4B86-9963-76E5AC398A3E
Related
About the following message:
Could not reserve enough space for 3145728KB object heap
I need some tips to understand what's going on
Points & Observations:
Running over Windows 10 x64 (16G Memory)
It only happens using this distribution: https://jdk.java.net/java-se-ri/8-MR3
It works fine using the build from AdoptOpenJDK: https://adoptopenjdk.net/?variant=openjdk8&jvmVariant=hotspot
At pom.xml, I've tried to add the following line: <extraJvmArgs>-Xms1G -Xmx4G -Xss1M -XX:-UseGCOverheadLimit -XX:MaxHeapSize=4G</extraJvmArgs>. But it "complains" The specified size exceeds the maximum representable size. (The original Xmx and MaxHeapSize was 3G)
Main Objective: To compile a project that was done previously using Oracle JDK8 with the Open JDK8
Any "lights"?
------ Edit
arg -d64 returns Error: This Java instance does not support a 64-bit JVM.
Maybe it's 32 bits the compilation from Java website?
What does this option do in docker file?
ENTRYPOINT java -XX:+UseContainerSupport $JAVA_OPTIONS -jar /myapp.jar
Will the docker container start without this parameter?
I checked one article which says
enable memory support
but it is still not clear to me.
Starting from Java 10, this parameter (which is enabled by default) is used to make the JVM take the container memory limits into account when allocating the heap size, not the host machine configuration.
This option was backported to Java 8:
https://www.oracle.com/technetwork/java/javase/8u191-relnotes-5032181.html
Examples:
If you run:
docker run **-m 1gb** openjdk:8u131 java -XshowSettings:vm -version
The result is going to be (on my machine Ubuntu with 8gb)
Max. Heap Size (Estimated): 1.68G
I set a memory limit for the container but it ignored and used the host config (it uses by default total memory/4)
Now if I run the version that has the new feature (link above) you can see that the container memory limite was taken into account:
docker run **-m 1g** openjdk:8u191-jre-alpine java -XshowSettings:vm -version
Result (total memory / 4):
VM settings:
Max. Heap Size (Estimated): 247.50M
Ergonomics Machine Class: server
Using VM: OpenJDK 64-Bit Server VM
openjdk version "1.8.0_191"
At the time I'm writing this the LATEST version of the openjdk:8 image is 222 so you can use this version. That has the feature included.
For more information:
Explains this flag use in Java 10: https://medium.com/adorsys/jvm-memory-settings-in-a-container-environment-64b0840e1d9e
Using this flag with Java 8: https://blog.softwaremill.com/docker-support-in-new-java-8-finally-fd595df0ca54
Yes. The container will start without -XX:+UseContainerSupport.
-XX:+UseContainerSupport is used to allocate a larger fraction of memory.
To prevent the JVM adjusting the maximum heap size when running in a container, set -XX:-UseContainerSupport.
In addition to that, https://www.eclipse.org/openj9/docs/xxusecontainersupport/ might be helpful.
I'm trying to increase value of heap size of my jvm, but it doesn't work. Could anybody help me with this geek problem?
My configuration are follow: Windows 7 x64, 4 GB, i3 CPU
When I try something like -Xmx2000M I have nothing
Where are my errors?
I think you are expecting this.
$ java -Xmx2000M -Xms1000M -XshowSettings:all
VM settings:
Min. Heap Size: 1000.00M
Max. Heap Size: 1.95G
Ergonomics Machine Class: server
Using VM: Java HotSpot(TM) 64-Bit Server VM
Your command is half correct. You need to specify what you want to run with an increased heap size. Something like this
java -Xmx2000M -Xms1000M -jar <jar-file-name>.jar
you need to specify as well which class/jar you want to run. You cannot just increase the heap size per default for all java pplications. Instead you have to edit the command line of the program you are trying to run.
The error you have got in the last screen shot is about unavailability of the class file to run.
You should provide class file which includes main function while running java command.
java -Xmx2000M -Xms1000m MyClass
Considering you have MyClass.class in your classpath.
You need to provide something for JVM to run with these new settings.
The arguments you are using only configure the JVM, it still needs whatever jar or class file you want to run.
To permanently configure JVM profile on windows, follow these Instructions. The settings tool will let you edit runtime parameters:
may be I am late)
But I think you can use it. In IDEA choose Edit Configuration... on drop-down list(look on picture below). And then type in VM Options your parameters -Xmx2000M -Xms1000M.
How to find Edit Configuration on IDEA
How can I trigger a heap dump for a Java 7 VM running on Linux without having a JDK installed?
In earlier versions of Java it was possible to set the -XX:+HeapDumpOnCtrlBreak JVM option and then trigger a heap dump by using kill -QUIT <pid>. I have been unable to get this to work with Java 7. Is there an equivalent to this without needing the JDK installed to get JVisualVM or jmap.
VM option -XX:+HeapDumpOnCtrlBreak is no longer listed at http://www.oracle.com/technetwork/java/javase/tech/vmoptions-jsp-140102.html. So, I conclude that it's no longer supported.
From http://www.oracle.com/technetwork/java/javase/tech/vmoptions-jsp-140102.html:
Options that are specified with -XX are not stable and are subject to
change without notice.
You can generate a core dump with gcore, move it to another machine, and attach jmap to generate hprof file as described in Core dump taken with gcore, jmap conversion to hprof file format fails with Error message
See also accepted answer.
I am using the G1 garbage collector with JDK1.7.0, but the VM does not recognize the option G1YoungGenSize. Specifically, when I run:
java -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1YoungGenSize=512m ...
I get the following error:
Unrecognized VM option 'G1YoungGenSize=512m'
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.
I have also tried it with a "+" sign before G1YoungGenSize, as some of the G1 documentation lists it that way:
java -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:+G1YoungGenSize=512m ...
But I get the same error.
I have tried older JDKs, including 1.6 update 18 through 21. It seems that G1YoungGenSize is recognized through update 20, and breaks beginning with 21 and through the latest 1.7 build (snapshot dated August 19, 2010).
Does anyone know what could be causing this error?
This looks to have changed about 6 months ago:
6928065: G1: use existing command line parameters to set the young generation size
http://hg.openjdk.java.net/jdk7/jdk7/hotspot/rev/a1c410de27e4
Changes made for 1.6 here:
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6928065
To be consistent with the other GCs, G1 should observe UseAdaptiveSizePolicy to decide whether to auto-tune the young generation size. NewSize / MaxNewSize (and also -Xmn) should dictate the initial max size.