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From Jess Holle <>
Subject Re: Memory usage Tomcat 3.3 vs 5.5
Date Tue, 25 Apr 2006 21:53:38 GMT
Remy Maucherat wrote:
> Abhi Karmos wrote:
>> Has anybody looked in the code where the DescriptorSupport class is 
>> used? 22 thousand of these things is simply absurd. Nearly 100 
>> thousand DescriptorSupport.ValueHolder objects is even crazier. My 
>> guess is that the HashMap usage is related to the DescriptorSupport.
> It is completely irrelevant compared to the memory usage of a single 
> "modern" web application, and at the same time it provides a useful 
> monitoring feature without being intrusive coding wise. Sure, we could 
> use standard MBeans, but the code would then be a mess. I don't 
> understand the point of bothering with this sort of stuff when there's 
> so little benefit.
Despite my tone in my previous e-mail on this thread, I tend to agree 
with Remy that the Tomcat folk have bigger fish to fry.  An extra 10MB 
of overhead is not the top priority for most Tomcat users.

Even without using standard MBeans I could certainly see dynamic MBeans 
with per-target-object-class caching eliminating most of this additional 
memory footprint.  Modeled MBeans are likely as capable of this as any 
other dynamic MBeans -- and if not that would be a reason not to use 
them in *future* projects.  [Commons "Dynamic" anyone?]

All the same, the MBeans generally do what's needful in Tomcat and I'd 
thus hate to see any "cleanup" in this area take precendence over "real" 
> If you want the smallest web container in terms of memory usage or 
> size, I think you should not be using Tomcat. Tomcat is more geared 
> towards speed, GC friendliness and feature completeness than memory 
> usage.

I notice that many of the Tomcat MBeans actually provide fairly useful 
attribute and MBean descriptions.  I also notice a good number of MBeans 
with no MBean-level description, however.  Same for operations, 
operation parameter names and operation parameter descriptions.  Fixing 
this seems like a higher priority than introducing MBean 
descriptor/MBeanInfo sharing at this point.

Jess Holle

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