In RAD, is there a way to forcibly run garbage collector on the jvm that is running the RAD itself? If not, can I run a java program that will connect to the RAD jvm and trigger its garbage collector?
Kaushik,
Eclipse has for a while now allowed to view the Heap Status of the JVM that it is running on. It is available on all products built on top of it.
Go to Prefernces -> General and check Show Heap Status.
To the lower right of the screen you should find the heap info and then a trash can.
You can click on the trash can to request eclipse/RAD to run a GC. I believe this is what you are looking for!
HTH
Manglu
Related
I am adding JVM args by using -XX:MinHeapFreeRatio and -XX:MaxHeapFreeRatio to see the GC behavior changes. I got some explanations here (what is the purpose of -XX:MinHeapFreeRatio and -XX:MaxHeapFreeRatio)
The question is how could I get the memory usage picture in the answer. I wanna make sure the modifications I made can really change the GC behavior.
It is a tool called VisualVM
There are some other alternatives such us JConsole or Java Mission Control
My project has started using java 8 from java 7.
After switching to java 8, we are seeing issues like the memory consumed is getting higher with time.
Here are the investigations that we have done :
Issues comes only after migrating from java7 and from java8
As metaspace is the only thing related to memory which is changes from hava 7 to java 8. We monitored metaspace and this does not grow more then 20 MB.
Heap also remains consistent.
Now the only path left is to analyze how the memory gets distributes to process in java 7 and java 8, specifically private byte memory. Any thoughts or links here would be appreciated.
NOTE: this javaw application is a swing based application.
UPDATE 1 : After analyzing the native memory with NMT tool and generated a diff of memory occupied as compare to baseline. We found that the heap remained same but threads are leaking all this memory. So as no change in Heap, I am assuming that this leak is because of native code.
So challenge remains still open. Any thoughts on how to analyze the memory occupied by all the threads will be helpful here.
Below are the snapshots taken from native memory tracking.
In this pic, you can see that 88 MB got increased in threads. Where arena and resource handle count had increased a lot.
in this picture you can see that 73 MB had increased in this Malloc. But no method name is shown here.
So please throw some info in understanding these 2 screenshot.
You may try another GC implementation like G1 introduced in Java 7 and probably the default GC in Java 9. To do so just launch your Java apps with:
-XX:+UseG1GC
There's also an interesting functionality with G1 GC in Java 8u20 that can look for duplicated Strings in the heap and "deduplicate" them (this only works if you activate G1, not with the default Java 8's GC).
-XX:+UseStringDeduplication
Be aware to test thoroughly your system before going to production with such a change!!!
Here you can find a nice description of the diferent GCs you can use
I encountered the exact same issue.
Heap usage constant, only metaspace increase, NMT diffs showed a slow but steady leak in the memory used by threads specifically in the arena allocation. I had tried to fix it by setting the MALLOC_ARENAS_MAX=1 env var but that was not fruitful. Profiling native memory allocation with jemalloc/jeprof showed no leakage that could be attributed to client code, pointing instead to a JDK issue as the only smoking gun there was the memory leak due to malloc calls which, in theory, should be from JVM code.
Like you, I found that upgrading the JDK fixed the problem. The reason I am posting an answer here is because I know the reason it fixes the issue - it's a JDK bug that was fixed in JDK8 u152: https://bugs.openjdk.java.net/browse/JDK-8164293
The bug report mentions Class/malloc increase, not Thread/arena, but a bit further down one of the comments clarifies that the bug reproduction clearly shows increase in Thread/arena.
consider optimising the JVM options
Parallel Collector(throughput collector)
-XX:+UseParallelGC
concurrent collectors (low-latency collectors)
-XX:+UseConcMarkSweepGC
use String Duplicates remover
-XX:+UseStringDeduplication
optimise compact ratio
-XXcompactRatio:
and refer
link1
link2
In this my answer you can see information and references how to profile native memory of JVM to find memory leaks. Shortly, see this.
UPDATE
Did you use -XX:NativeMemoryTracking=detail option? The results are straightforward, they show that the most memory allocated by malloc. :) It's a little bit obviously. Your next step is to profile your application. To analyze native methods and Java I use (and we use on production) flame graphs with perf_events. Look at this blog post for a good start.
Note, that your memory increased for threads, likely your threads grow in application. Before perf I recommend analyze thread dumps before/after to check does Java threads number grow and why. Thread dumps you can get with jstack/jvisualvm/jmc, etc.
This issue does not come with Java 8 update 152. The exact root cause of why it was coming with earlier versions is still not clearly identified.
this is my first post in stack overflow forum. we are recently experiencing some Java OOME issues and using jvisualvm, yourkit and eclipse mat tools able to idenify and fix some issues...
one behavior observed during analysis is that when we create a heapdump manually using jconsole or jvisualvm, the used heap size in jvm reduces dramatically (from 1.3 GB to 200 MB) after generating the heapdump.
can some one please advise on this behavior? this is a boon in disguise since whenever i see the used heapsize is >1.5GB, i perform a manaul GC and the system is back to lower used heapsize numbers resulting in no jvm restarts.
let me know for any additional details
thanks
Guru
when you use JConsole to create the dump file, there are 2 parameters: The first one is the file name to generate (complete path) and the second one (true by default) indicates if you want to perform a gc before taking the dump. Set it to false if you don't want a full gc before dumping
This is an old question but I found it while asking a new question of my own, so I figured I'd answer it.
When you generate a heap dump, the JVM performs a System.gc() operation before it generates the heap dump, which is collecting non-referenced objects and effectively reducing your heap utilization. I am actually looking for a way to disable that System GC so I can inspect the garbage objects that are churning in my JVM.
I have apache-tomcat as my web server.
I want to check what heap size is allocated for jvm by linux.
Also from where, I can modify it.
A simple way on Linux is to run the following:
ps -ef |grep tomcat
Look for the starting and maximum JVM memory:
-Xms1024m -Xmx4096m
In this case it is allocating 1G on startup and the Maximum is 4G.
You can easily check the heap size memory allocation using JConsole, if you have a path to your jre/jdk set up correctly on the system you should be able to start it with command jconsole from anywhere.
For managing your heap memory allocation you can have a look here: http://javahowto.blogspot.com/2006/06/6-common-errors-in-setting-java-heap.html
The heap size used by Tomcat is defined in its configuration.
This is the place where you can both check and change it.
If you're unsure about where this configuration is saved, I'd suggest looking at the Tomcat documentation where this is explained together with all configuration values.
If you need more information from the server but cannot log into it interactively (or don't have a GUI or JMX set up etc) you can include javamelody in your POM file/libs and it will create a page at host:8080//monitoring with all kinds of good information, including heap size, GC statistics and permgen size.
This is NOT a safe thing to leave running in a production environment - if you need it all the time at least lock it down!
So the basics are I have Glassfish 2.1 and Java 1.6.0_15 and it will work for a few days but it eats up all the memory it can, seemingly no matter how high the max memory is set to. It's a 32-bit jvm with the max memory now at 4GB and it uses it all up quickly then thrashes with the garbage collector bringing throughput to a crawl. So after a few tries I got a 3GB heap dump and opened it with YourKit.
The usage on this server is a swing client doing a few RMI calls and some REST https calls, plus a php web site calling a lot of REST https services.
It shows:
Name Objects Shallow Size Retained Size
java.lang.Class 22,422 1,435,872 1,680,800,240
java.lang.ref.Finalizer 3,086,366 197,527,424 1,628,846,552
com.sun.net.sll.internal.ssl.SSLSessionImpl 3,082,887 443,935,728 1,430,892,816
byte[] 7,901,167 666,548,672 666,548,672
...and so on. Gee, where did the memory go? Oh, 3 million SSLSessionImpl instances, that's all.
It seems like all the https calls are causing these SSLSessionImpl objects to accumulate, but then they are never GC'ed. Looking at them in YourKit, the finalizer is the GC root. Poking around the web this looks very much like http://forums.sun.com/thread.jspa?threadID=5266266 and http://bugs.sun.com/bugdatabase/view_bug.do;jsessionid=80df6098575e8599df9ba5c9edc1?bug_id=6386530
Where do I go next? How do I get to the bottom of this?
This seems to be fixed now with an upgrade to the latest JVM. 1.6.0_18 fixes bug 4918870 which is related to this. Prior to upgrading the JVM, I had several heap dumps with 100,000-4,000,000 SSLSessionImpl, now there are usually less than 5000 instances.