Ron,
While you continue to load classes that are available for weaving they
will need to be resolved and the amount of byte-code that is held may
continue to rise. Also if you are doing profiling there will be a lot
of JoinPoint.Static part objects created. The weaver is not
multithreaded so it won't be allocating objects in the background.
Once we have worked out all the issues surrounding
ReflectionBasedReferenceTypeDelegate objects we can look at footprint
again. After that we can look at releasing byte-code but that will
take longer.
Cheers
Matthew Webster
AOSD Project
Java Technology Centre, MP146
IBM Hursley Park, Winchester, SO21 2JN, England
Telephone: +44 196 2816139 (external) 246139 (internal)
Email: Matthew Webster/UK/IBM @ IBMGB, matthew_webster@xxxxxxxxxx
http://w3.hursley.ibm.com/~websterm/
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Subject: RE: [aspectj-users] Garbage collector behavior
Hi Mathieu,
I have also noticed this phenomenon, e.g., there's about a 20% increase in
memory footprint on start up of Tomcat. However, after I have run a load
test I have seen the memory overhead rise to 100%. Now the interesting
thing
is that I see this effect even if I disable all my aspects at runtime
(with
&& if(enabled) tests). However, if I write a trivial aspect that just
prints
a message on staticinitialization of classes and deploy only that at
load-time, I see a normal memory profile under load.
I think the next step is to try to come up with a simplified example that
reproduces the issue we're both seeing... This will also help to make sure
it's not something like mistakenly holding on hard references in the
monitoring code (for both of us!)
There isn't a lot that's been written about this subject, since LTW is so
new... You can see some related tracking bugs
https://bugs.eclipse.org/bugs/show_bug.cgi?id=112817
https://bugs.eclipse.org/bugs/show_bug.cgi?id=113511
-----Original Message-----
From: aspectj-users-bounces@xxxxxxxxxxx
[mailto:aspectj-users-bounces@xxxxxxxxxxx] On Behalf Of Mathieu LEMAIRE
Sent: Wednesday, October 26, 2005 3:01 AM
To: aspectj-users@xxxxxxxxxxx
Subject: Re: [aspectj-users] Garbage collector behavior
Actually, memory issues I encounter do not appear at class-loading but
at runtime... My statistics are done amongst N runs of our program,
systematically discarding the first run to put JVM optims/weaving/class
loading aside.
Could you imagine any reason why the memory management would be affected
by the LTWeaver ?
Do you have any link describing the bytecode duplication you mentioned ?
Thanks a lot for your answers.
--
Mathieu
Ron Bodkin wrote:
>Hi Mathieu,
>
>I'm very aware of these issues. I'm working on a general framework for
>tracking performance in application using AspectJ
>(https://glassbox-inspector.dev.java.net/). I have been working with
Alex
>Vasseur and Matthew Webster to reduce the memory and startup time
overhead
>of this. This, of course, builds on past work that Adrian Colyer led with
>Andy Clement and Ron DiFrango if memory serves me right.
>
>Anyhow, I believe that the next stage of reducing overhead is Matthew's
>promising idea of using reflective proxy delegates for already loaded
>classes instead of storing multiple copies of bytecode for classes.
This is
>most easy to implement with bootstrap-loaded classes (think rt.jar).
>However, over time I think it will be important to have cacheing and to
>allow sharing of class-definition bytecodes when a class is loaded.
>
>I'm very interested in your statistics on the GC affects of LTW and
want to
>better understand where the extra memory is consumed.
>
>-----Original Message-----
>
>I'm implementing a framework to profile our program execution, that is,
>memory consumptions, durations...
>I use aspectJ (LTW mode) to instrumentate my classes.
>
>Here is my problem..
>I got memory issues when using aspectJ, comparing to a mode where I
>instrumentate my classes directly in the code (aspectJ is completely
>removed from this mode). Using aspectJ, memory consumptions of my
>program are much higher than without using it (eg 120Mo > 70Mo). Also
>profiling garbage collections, it seems that the GC collects much more
>when aspectJ is off (eg 4.5s > 2.3s).
>
>Do you have any clue for that to happen ?
>thanx !
>
>
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