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From David Jencks <>
Subject Re: Thinking about a 2.2 release
Date Wed, 22 Apr 2009 15:26:06 GMT

On Apr 22, 2009, at 6:58 AM, Bill Stoddard wrote:

> David Jencks wrote:
>> On Apr 15, 2009, at 10:42 PM, David Jencks wrote:
>>> I've been assuming that the classloader work Gianny and I have  
>>> been working on in my sandbox would get into 2.2.  At the moment I  
>>> think I have the classloader framework more or less working and  
>>> I'm going through the plugins working on setting up the required  
>>> jar dependencies.  Only some of them can be derived from maven  
>>> dependencies.  This is turning out to be a somewhat slow process.
>> I finally got the server to run with the one-classloader-per-jar  
>> setup.  After struggling with this for a couple of weeks and seeing  
>> the difficultly of correctly configuring classloaders I don't   
>> think we should put this into 2.2.  For one thing classloading  
>> seems to be pretty slow: it takes about 55 seconds to start the  
>> jetty-jee5 server.
> 55 seconds to start... that's really bad  in comparison to the  
> server today. The full Tomcat JEE5 assembly on my MBP will start in  
> something like 20 seconds.. a minimal assembly under 10 seconds.   
> I've been seeing reports that JBoss 5 is slow and bloated compared  
> to earlier releases... seems to be the natural evolution of app  
> servers.
> Is the performane hit related to the design (classloader per jar) or  
> something in how the design is implemented?

I had enough trouble getting the server to start.... I haven't done  
any profiling to find out what the slowdown is actually caused by.  I  
assume that its because the classloader graph is now about 4 to 8  
times larger and has a lot of duplication in it and no optimization.   
I heard a rumor somewhere once that in order to perform well osgi  
classloading needs indexing so a classloader knows where to look for a  
class it doesn't load itself.  I imagine we now have exactly the same  
problem.  I expect that with a bit of work -- such as actually using  
osgi -- classloading will be at least as fast as it was before these  

david jencks

> Bill

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