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From bugzi...@apache.org
Subject [Bug 55511] Reduce contention on WebappClassLoader
Date Sun, 08 Sep 2013 03:41:32 GMT
https://issues.apache.org/bugzilla/show_bug.cgi?id=55511

--- Comment #5 from Jason Koch <jasonk@bluedevel.com> ---
Having a little trouble building an isolated minimal case benchmark.

Background - my app, when profiled, shows ~30% of response time under load is
due to the classloader locking. App under profile is Java 6, Tomcat 6, on SPARC
but code has not changed since that time. My attempt to repro the issue with a
simple servlet that calls loadClass as the only item in the servlet does not
show contention. 

Possible causes - falsely showing this issue in my app, is not an issue under
Tomcat 8 for other reasons, attempting to repro on x86, can't drive enough work
onto the x86 server that I have (bandwidth saturated), issue may not really be
with WebappClassLoader but some parent item.

When I have applied a full CachingWebappClassLoader by subclassing it showed
significant benefits but I was unable at the time to hook up a JHM benchmark in
WebappClassLoader, seems to have a lot of dependencies with the container.

Here some additional results for a full subclass of WebappClassLoader - I made
a possibly flawed assumption that the reason WebappClassLoader with CHM did not
show issues was because I was not loading classes from JARs registered with
that loader (but instead loading classes via WebappCL to the system loader) 

http://fasterjava.blogspot.com.au/2013/08/caching-classes-from-classloader.html

Will continue investigating.

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