Konstantin, On 4/28/12 8:58 PM, Konstantin Kolinko wrote: > 2012/4/27 Christopher Schultz <ch...@christopherschultz.net>: >> All, >> >> I've been doing some memory profiling on my webapp to see where I can >> reduce our memory footprint a bit by combining equivalent objects. >> YourKit has some nice utilities to look for duplicate objects -- >> especially Strings. >> >> I can see that the string "java.lang.String" has lots of duplicates. >> Many of the ones I've inspected so far can be traced-back to >> catalina.mbeans.MBeanUtils and the registry of MBeans that it contains. >> >> Would anyone object to using String-interning to share copies of class >> names for MBeans? I could even restrict such interning to Strings that >> start with "java.lang" since those are probably the most-used ones, and >> those strings are probably already interned by all the RTTI >> infrastructure in the JVM anyway. > > I think that the string returned by class.getName() as well as field > and method names should be already interned by JVM. > > So instead of String.intern() it should be possible to call class.getName(). > :/
That's what I would have expected, but I can see logs of duplicate String values (like "java.lang.String" for instance), many linked from JMX beans. I haven't looked at the code, but I'll bet the string values from directly from the XML files and aren't resolved against actually Class objects ... that would improve performance a bit during deployment. > I am OK with your proposal, but I do not expect much savings from > getting rid of those duplicates. Does YouKit show some estimates? It did, but I closed it long ago so I'll have to re-check. IIRC, it was a couple of MiB. Of course, it's not feasible to check 100% of them because there were so many copies. I can hack a bit at Tomcat and see what percentage of them disappear. Then I'll know whether such a change in Tomcat actually has a meaningful impact. Thanks, -chris
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