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Posted to dev@commons.apache.org by Morgan Delagrange <md...@yahoo.com> on 2003/12/17 17:37:00 UTC
[Jelly] memory leak
Hey all,
We recently discovered a pretty serious memory
inefficiency in Jelly. Although it's not listed in
the Jelly issue tracker, there is a reference to it
elsewhere
(http://jira.codehaus.org/secure/ViewIssue.jspa?id=11194).
Basically Jelly uses ThreadLocal variables as a
performance optimization in two places: once in the
base TagScript class to allow thread-safety for Script
instances and once in the JellyContext class to cache
XML parser instances.
The problem is that in environments using thread
pooling (e.g. Tomcat), the ongoing demands on memory
are considerable; basically many of the tags you
create is stored in memory in perpetuity for each
thread in the pool. Since the thread is never
garbage-collected, the tags stick around too. This
can easily lead to an out-of-memory condition.
Looking at the code (which admittedly I do not 100%
understand), I don't see a good way to stop using
ThreadLocal variables without breaking thread-safety
for Script objects. This is not good. However,
eating up all the JVM's memory is also not ideal. I
will enter this as a bug, but this is the kind of
problem that needs to be addressed sooner rather than
later.
- Morgan
=====
Morgan Delagrange
http://jakarta.apache.org/commons
http://axion.tigris.org
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Re: [Jelly] memory leak
Posted by Morgan Delagrange <md...@yahoo.com>.
Aha, Scott Howlett pointed us to an existing bug that
descibes this issue and includes a patch! It looks
good to me, so I'm applying it now.
- Morgan
--- Morgan Delagrange <md...@yahoo.com> wrote:
> Hey all,
>
> We recently discovered a pretty serious memory
> inefficiency in Jelly. Although it's not listed in
> the Jelly issue tracker, there is a reference to it
> elsewhere
>
(http://jira.codehaus.org/secure/ViewIssue.jspa?id=11194).
> Basically Jelly uses ThreadLocal variables as a
> performance optimization in two places: once in the
> base TagScript class to allow thread-safety for
> Script
> instances and once in the JellyContext class to
> cache
> XML parser instances.
>
> The problem is that in environments using thread
> pooling (e.g. Tomcat), the ongoing demands on memory
> are considerable; basically many of the tags you
> create is stored in memory in perpetuity for each
> thread in the pool. Since the thread is never
> garbage-collected, the tags stick around too. This
> can easily lead to an out-of-memory condition.
>
> Looking at the code (which admittedly I do not 100%
> understand), I don't see a good way to stop using
> ThreadLocal variables without breaking thread-safety
> for Script objects. This is not good. However,
> eating up all the JVM's memory is also not ideal. I
> will enter this as a bug, but this is the kind of
> problem that needs to be addressed sooner rather
> than
> later.
>
> - Morgan
>
>
> =====
> Morgan Delagrange
> http://jakarta.apache.org/commons
> http://axion.tigris.org
>
>
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> To unsubscribe, e-mail:
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> For additional commands, e-mail:
> commons-dev-help@jakarta.apache.org
>
=====
Morgan Delagrange
http://jakarta.apache.org/commons
http://axion.tigris.org
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