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How can I disable Java garbage collector ?

Answer 1

+10 A:

GC only kicks in when JVM is short on memory, so you either GC or die. Try turning on verbose GC and see if it actually takes significant amount of time.

java -verbose:gc

unbeli 2010-05-28 07:53:41

Umm, then maybe I could use a commandline switch to give it more memory and so increase the chance the GC does not kicks in..

Nelson 2010-05-28 08:00:47

Yes, you will know if you need to do that after analyzing the output of verbose:gc. That's the first step.

unbeli 2010-05-28 08:01:58

+1 for "test, don't guess". The time diff could be something completely unrelated, like I/O contention or some CPU heavy process kicking in.

gustafc 2010-05-28 08:08:32

Answer 2

+1 A:

Are you sure that it is garbage collection causing the slowdown? Have you run java with -verbose:gc to see what is happening?

You cannot disable garbage collection on the JVM. You could however look at tuning the garbage collector for better performance.

Mark 2010-05-28 07:56:30

Answer 3

+2 A:

You can use the -Xmx option to set the maximum heap size; using a larger heap should prevent the VM from runnning out of memory and, thereby, requiring garbage collection so soon.

Michael Aaron Safyan 2010-05-28 07:59:32

Just setting -Xmx won't make any difference. You actually need to set -Xms as well since you want to control the initial heap size.

Stephen C 2010-05-28 08:14:00

Answer 4

+11 A:

There is no way to disable garbage collection entirely. Garbage collection is only run when the JVM runs out of space, so you could give the program more memory. Add these command line options to the Java command

-Xmx256M -Xms256M

This gives the program 256Mb of ram (the default is 64Mb). Garbage collection will not take 3 seconds for a default size JVM though, so you might want to investigate more closely what the program is doing. Yourkit profiler (http://www.yourkit.com/) is very useful for figuring out what is taking a long time.

Ceilingfish 2010-05-28 07:59:33

Answer 5

+16 A:

It sounds like you are trying to save time, but going about it the wrong way. The time saved in disabling garbage collection would be trivial (for a single task) compared to the time taken to launch and shutdown the java process. You might want to consider having a java process launch that you can ask multiple times to do the work you require if run-time performance is your goal.

jowierun 2010-05-28 08:03:56

Good one... it would save jasper initialization too, I think.

helios 2010-05-28 08:15:20

Yes, this is good approach although more work to do, I would have to code a kind of daemon that would listen on sockets and so on.. besides this "daemon" would have to be restarted once in X days.. cause java leaks memory in the long run (from my experience)..

Nelson 2010-05-28 08:20:55

@Nelson Consider seeing if you can use something like Mule to host your Java processes and let that handle all of the communications for you. The idea being that you just need to embed your JasperReports as a service that the ESB can host and route requests to as necessary.Mule: http://www.mulesoft.com/mule-esb-open-source-esb

Trevor Tippins 2010-05-28 08:28:31

@Nelson Java doesn't leak memory per se. We have java deamons running for months, only restarted for application updates or system downtimes. If your Java programs are leaking, try to use a profiler. There are other options than open the socket yourself. There is ActiveMQ/JMS, JMX, or you could create a webservice for it, maybe jetty would be interesting.

Hardcoded 2010-05-28 08:46:24

Answer 6

A:

As everyone as said you can't disable GC in the JVM, which makes sense right, because if you could there'd be memory leaks due to java not having an explicit way for the developer to delete the heap data.

Do you have access to the source of this java binary? If so it might be worth analysing it and seeing if there's any bottle-necks which could be better written to cut down on GC activity. This could be done with most java profilers, like JProbe for example.

toby 2010-05-28 08:23:15

the java binary is very simple, it just retrieve commandline paraemeters and make calls into jasperreport functions to create the report, which is passed to the System.out outputstream where the PHP read it through 'passthrough' function. So the the time is spent on Jasperreport proccessing the report, thats how I wanted a java general speedup.

Nelson 2010-05-28 08:28:40

It looks like controlling the JVM GC settings is your only avenue here then.

toby 2010-05-28 08:39:50

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How can I disable Java garbage collector ?

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