 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
Java Forum / General / October 2007Memory leak in Java app
I have a Java app, running on Windows, with a medium amount of C++ wrapper code doing various arcane and boring things. JProfiler swears that there isn't a memory leak in the Java. Purify claims that there isn't a memory leak in the C++. According to ProcessExplorer, however, we leak memory (or rather, the Private Byte and Working Set keep rising). Some of this might be induced by memory fragmentation, I suppose, but other than that and the thought that Sun's JVM might leak memory (possible?), I'm not sure where to go. I'm currently using Sun's 1.5 JVM. Client and Server mode doesn't make much of a difference (the amount of memory used goes down, but the increase remains). I haven't tested extensively with 1.6, but saw essentially the same behavior with my quick look. Is futzing with the GC parameters going to accomplish anything? Is this just expected behavior? Is the only solution to kill and resume the app on a regular basis? Alan  SignatureDefendit numerus > I have a Java app, running on Windows, with a medium amount > of C++ wrapper code doing various arcane and boring things. [quoted text clipped - 16 lines] > > Alan Only assume you're leaking memory if over a sufficient time period, you get OOM exceptions. Java is a Garbage Collected environment, which means that some objects may just hang around until the GC decides its time to clean them up. Looking at the java processes memory consumption doesn't tell you what is actually in use. The garbage collector usually doesn't try very hard until the used memory gets to be very close to "full" for the currently allocated heap size. In other words, its normal to have memory usage creep up slowly and then, with no warning or explanation, drop down to normal levels again. SignatureDaniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/> >> I have a Java app, running on Windows, with a medium amount >> of C++ wrapper code doing various arcane and boring things. [quoted text clipped - 10 lines] >doesn't try very hard until the used memory gets to be very close to >"full" for the currently allocated heap size. I'm aware of that, but there may be some subtlties in the Java GC that I'm missing. JProfiler claims that the heap never grows beyound about 10MB. I see regular garbage collections occurring which generally reduce my consumption from about 9MB to about 6MB. I can run the system all day and this won't change. However, Process Explorer insists that my app, which started off using 30MB of private memory, is now using 60MB. Forcing a GC via JProfiler doesn't do anything to change this. Obviously using JProfiler is going change the system behavior and mess with these numbers blah blah Heisenberg. I realize this is not an exact science. Alan SignatureDefendit numerus > and this won't change. However, Process Explorer insists that my app, > which started off using 30MB of private memory, is now using 60MB. Forcing [quoted text clipped - 3 lines] > with these numbers blah blah Heisenberg. I realize this is not an exact > science. Roedy's link explains that not calling dispose() on GUI objects results in the underlying (native) objects being retained by the OS. Could be something like that. You may have to look beyond the JVM and see what the rest of the system is allocating on your behalf. I'm not an expert in Windows heap analysis by any means, but if you find some good info debugging Windows heaps please post up what you find. :-) >> and this won't change. However, Process Explorer insists that my app, >> which started off using 30MB of private memory, is now using 60MB. Forcing [quoted text clipped - 6 lines] >Roedy's link explains that not calling dispose() on GUI objects results >in the underlying (native) objects being retained by the OS. Mmm. I'm not using GUI objects but the same principles could apply to other objects. I'll see if Purity can give me any information there. Alan SignatureDefendit numerus >>> and this won't change. However, Process Explorer insists that my app, >>> which started off using 30MB of private memory, is now using 60MB. Forcing [quoted text clipped - 8 lines] > Mmm. I'm not using GUI objects but the same principles could apply to > other objects. I'll see if Purity can give me any information there. Did you run the JVM with verbose GC trace? Did it tell anything interesting? Btw, 60MB does not sound much nowadays. I believe the JVM's default for -Xmx is 64MB so you could expect it to grow a bit more without having to worry. Kind regards robert > Mmm. I'm not using GUI objects but the same principles could apply to > other objects. I'll see if Purity can give me any information there. > > Alan You may also want to take a look at some of the IO classes with associated close() methods... these objects often have (in some cases significant) native memory associated with them. If you explicitly call close() the native memory is freed; if you don't, the memory doesn't get freed until the object finaliser gets called (which if the object has been promoted to the old area may never happen). I've seen one deviant case where we got OutOfMemory because of this even though there was plenty of free memory in the Java heap. You may be able to allay this particular problem by tweaking GC parameters (if it's outside your code) - as you can cause objects to live for longer without getting promoted if this is the problem. However (IMO) best practice is always to call a close() or dispose() method if it exists (preferably in a finally block...) Dave > In article <I_idnSdha7zskLzanZ2dnUVZ_hWdn...@wavecable.com>, > [quoted text clipped - 28 lines] > -- > Defendit numerus This looks like that the leak is not in Java. To be sure the easiest way to find out whether it's a leak in Java is to get the SAP Memory Analyzer at https://www.sdn.sap.com/irj/sdn/wiki?path=/display/Java/Java+Memory+Analysis. It's free and will be open sourced soon(check my blog here https://www.sdn.sap.com/irj/sdn/weblogs?blog=/pub/wlg/7637) Regards, Markus >I have a Java app, running on Windows, with a medium amount >of C++ wrapper code doing various arcane and boring things. >JProfiler swears that there isn't a memory leak in the Java. >Purify claims that there isn't a memory leak in the C++ but you may have some packratting. See http://mindprod.com/jgloss/packratting.html SignatureRoedy Green Canadian Mind Products The Java Glossary http://mindprod.com Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
|
Reply to this Message
|
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2008 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.