Joel Oliveira | |
Software Product Assurance Manager | |
Do you rely on your software? |
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Hi,
is there any literature available regarding the duplicate Strings problem? I ask this because to my knowledge Strings are unique within a VM and there's nothing I found by a quick search in the web that differs from this statement (Maybe I used the wrong query words…):
"The JVM recognises that the two string literals are identical and only creates a single instance. This is sensible on the part of the JVM for performance and memory reasons"
So it would be great, if someone has a link that describes how this problem can happen.
Ciao
Frank
Hi,
Yesterday I had a memory analyzing session with an expert from the Eclipse Memory Analyzer team. We had a look at a heap dump of the RAP Demo Application with a couple of hundred simulated users.
Here are the most important results:
Memory consumption of the RAP framework is very reasonable! This is a great result. Still, there is always some room for improvement:
There are many duplicated Strings. A big chunk of those are from widget ids. Moving the implementation to use String.intern() will probably be a quick and efficient way to improve memory consumption (only the S.. JVM 1.4 is inefficient with String.intern() ). Another alternative might be using our own data structure, if we restrict ourself to UTF-8 we need only 1 Byte per character instead of 2 Byte for String.
Another area for potential improvement is our use of Hashmaps, We have 172.000 completely empty hashmaps (530.000 in total).
It seems that WidgetAdapter is contributing significantly to the large amount of empty hashmaps.
From my point of view this is not high priority at the moment, but could be researched in one of the upcoming releases.
P.S: See also the interesting posting here:
