jvm conf for normal gc at high load

I have server application based on Netty. It decode message (from json) and send开发者_Go百科 it back to the client (simple echo). When i have a lot of messages send from one client (more than 15k/second) garbage collector don't start and memory usage grown up.

How can i configure jvm to decrease gc pauses and decrease memory usage?

Your description sounds like a memory leak. Does the garbage collector eventually start, or do you end up with an OutOfMemoryError?

If you don't, then it sounds like you're running into a situation where objects are living long enough to get into the tenured generation (I'm assuming Sun JVM here). And the solution to that is to increase the size of the young generation relative to the tenured generation.

Here's a link that explains the Sun JVM generational collector (it's for the 1.5 JVM, but I believe that the options haven't changed for 1.6): http://www.oracle.com/technetwork/java/gc-tuning-5-138395.html

The options that you would want to experiment with are NewRatio, which is the ratio between the young and tenured generations, and SurvivorRatio, which is the ratio between Eden and the two survivor spaces. I might try the following:

• -XX:NewRatio=1 gives the young generation half of the object heap
• -XX:SurvivorRatio=2 makes each survivor space be half that of Eden

These two settings will make the "Eden" space for new objects take 1/4 of the heap. This is pretty big, so hopefully most objects will spend their entire lives in Eden. The survivor ration gives another 1/4 of the heap to the survivor spaces (1/8 to each), to hold objects with a medium life.

Of course, don't blindly set options. Instead, use jconsole (part of the JDK distribution) to see what's really happening with your heap. You might find that the default survivor ratio of (1:6) is better than what I've suggested.

To configure jvm to decrease gc pauses and decrease memory usage, you need to choose an appropriate GC collector. CMS is a low pause collector. You can set -XX:+UseConcMarkSweepGC to enable it. And, you can fine-tune other parameters such as

-XX:+UseCMSInitiatingOccupancyOnly
-XX:CMSInitiatingOccupancyFraction=nn

to control GC pause.