Clear memory usage

Question

Hello,
I have created a web app. I'm using Ubuntu 10.04, Netbeans 6.9 and Tomcat 6 server.
My application is based on Apache Lucene search. (I'm not sure, maybe Lucene is causing my problem, but I doubt it.)
My problem is:
When I search for some data, for e.g a word which is String, I store the results in ArrayLists. But everytime I send a request to servlet, I clear arraylists by doing this:
ArrayList.clear();But my memory usage is rising on every search. And finally, I get my system using full memory.
Mem:
total       used       free     shared    buffers     cached
4025       3860        164          0         54       1267What could cause this?
Maybe I have to clear "cached" somehow?
Edited by: peliukasss on Aug 24, 2010 11:39 AM

Answer 1

peliukasss wrote:
My problem is:
When I search for some data, for e.g a word which is String, I store the results in ArrayLists. But everytime I send a request to servlet, I clear arraylists by doing this:
ArrayList.clear();
That's most likely unnecessary, unless you're keeping references to those arraylists needlessly somewhere. You're not storing them into the session are you?
But my memory usage is rising on every search. And finally, I get my system using full memory.
Mem:
total       used       free     shared    buffers     cached
4025       3860        164          0         54       1267What could cause this?The operating system uses the memory for caching and such if it can, because free memory has no intrinsic value. It can and will get rid of some cache if memory is required.
Maybe I have to clear "cached" somehow?No, that's what the operating system keeps cached. Java has nothing to do with that.
The actual used memory is seen on the second line, which counts out the buffers and cache, such as on my machine:
             total       used       free     shared    buffers     cached
Mem:          3837       3766         71          0         51       1640
-/+ buffers/cache:       2074       1762
Swap:        11240        378      10862Even though it might seem I have only 71 megabytes of free memory, there's actually 1.7GB free.
You can give less memory for tomcat if you don't want it to go that high, look into the starting options. But there's nothing bizarre about what you're seeing.