[opencms] [opencms-dev] Optimizing OpenCMS performance.

[Nigel Kersten]

On 22/06/2006, at 6:58 AM, <justin.spies at sbcglobal.net>  
<justin.spies at sbcglobal.net> wrote:

> To answer your question about the garbage collection issues, I've  
> still seen many posts about garbage collection in Java 1.5.  In  
> fact, there is a known garbage collection bug in JDK1.5 that is not  
> scheduled to be fixed until 1.5_08.

ahah, I'm on:

java version "1.5.0_06"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_06-112)
Java HotSpot(TM) Client VM (build 1.5.0_06-64, mixed mode, sharing)

A few people have mentioned that there are some PPC specific problems  
with garbage collection, so I'm toying with the idea of moving  
OpenCMS over to one of my Linux x86 boxes rather than a PPC Xserve.

> Also, despite the performance improvements (I've read of people  
> using 12GB heap sizes on 64bit machines, but have no way to verify  
> this), the system still spends a large amount of time processing  
> the memory.  I'm working on a project now that involves a BEA  
> server using the Sun 1.4 JDK and a full GC of a 400MB heap is still  
> taking about 1.0 - 1.5 seconds.  From what I've read, there are two  
> approaches to tuning GC--the first is to setup the system to  
> perform frequent, but short (low pause) collections (i.e. using a  
> small heap) and the other is to tune the system using infrequent  
> but long collections (i.e., using a large heap.)  The route taken  
> depends on the application.

So unlike with java prior to 1.5, you can't actually modify the  
garbage collection method with -Xincgc as you could with 1.4, and  
this is all up to the application developer?

It really seems like having those regular expressions I mentioned  
seem to trigger some kind of bug where CPU usage goes through the  
roof. I've disabled them for now, but will try and test them out with  
garbage collection logging on so that I can see if that's the problem.

I've gone down to 128-512Mb memory allocation, and that seems to be  
ok. Setting up mod_cache with apache in front has made the biggest  
difference in terms of performance. It's nice to be able to have a  
system that responds happily to content-header settings regarding  
caching, so you can tune the cache for different areas of the site.

thanks for the response.

-- 
Nigel Kersten [Senior Technical Officer]
College of Fine Arts, University of NSW, Australia.
CRICOS Provider Code: 00098G