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From Santiago Gala <sg...@hisitech.com>
Subject Re: Jetspeed Performance tips
Date Fri, 21 Mar 2003 18:38:08 GMT
Shan Gopalakrishnan wrote:
> We observed few more things.  I'm posting this to the best interest to 
> mature the framework further than what it is currently today.
> Definitely this is not criticism.

Feel free to criticize. It is the only way we have to improve Jetspeed.

> We are seeing the Garbage collector (Major GC) getting triggered 
> frequently as I think huge set of objects are getting created.

Some profiling could be handy. AFAIK:

Wrappers for security are not recycled (they *must* be inmutable)
PortletSets are created new for every request, due to threading issues.
--> Both kinds of objects should be claimed from "young" space, unless 
we are missing some "nullification" in permanent objects.

The registries are reloaded every 5 minutes, meaning a whole set of 
Castor marshalling and new objects going on (and fading) happens. If you 
don't have registries that change a lot, you could make this interval 

Every time DiskCacheDaemon runs, it will call xerces and xalan to 
transform RSSPortlets.

Every 30m you will have tomcat sessions expiring. If your testing does 
not keeps the sessions, you will be filling a lot of memory with fake 
sessions which will never be reused. I imagine you are using a testing 
framework that keeps sessions for a number of hits per "user".

A lot of other objects could come from either Velocity ASTs, Torque 
peers or other places. Even from your portlets ;-)

About Spring 2001 some profiling and tuning was done, by the IBM team, 
David, Raphael and myself. I don't know of other such effort since then. 
This led to rundata and some other objects pooling in turbine, and some 
changes of String concatenation to StringBuffer.append(). We also 
discovered a lot of duplicated initializations and similar stuff. It is 
always funny to see how big bugs can hide in code.

But the behaviour you are seeing looks more like the bug I pointed below 
or a bug in the hotspot compiler. Could you switch temporarily to jdk 
1.3.1_07 or 1.4.0_XX and see if the same happens? (According to reports 
in cocoon-dev, 1.4.0 does not have the StringBuffer bug)

> This could be inherited from Turbine implementation.  We are now playing 
> with the various options in the Garbage Collector
> part of the JDK 1.4.1, which is running the GC parallel, setting high 
> heap size,  giving some % for young generation Vs old generation etc.
> Most likely to my knowledge the minor GC looks only the younger 
> generation area as we didn't see any benefits in increase the
> % of younger generation.  Apparently the spike still remains and gives 
> poor response time just that the symptom happens way early
> or later during the tests depending on the heap size and GC configuration.

If the problem is that some "bunches" of objects get into "old" space 
because they are pointed by persistent objects, then a juditious ammount 
of "= null" on recycling can help a lot. I've just checked 
DefaultJetspeedRunData and it is disposed properly (unless something is 
broken down in Turbine and it is not really disposed).

> - Shan
> At 12:43 PM 3/21/2003 +0100, Santiago Gala wrote:
>> Santiago Gala wrote:
>>> Shan Gopalakrishnan wrote:
>> (...)
>>>> Has any one done similar  tests, did you observe something like that?
>>>> Do you have any suggestions where to look further?  This is on 
>>>> Solaris 8 with JDK 1.4.1_01, Tomcat 4.1.18 and Jetspeed 1.4b3.
>> http://developer.java.sun.com/developer/bugParade/bugs/4724129.html
>> may well be related. A very scary bug, BTW, which can explain why I'm 
>> seeing ant or maven builds hung forever and claim all memory in my 
>> machine. Ans also server VM crashes with OutOfMemory after tomcat 
>> context reloading.

Santiago Gala
High Sierra Technology, S.L. (http://hisitech.com)

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