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From Jeffrey Janner <Jeffrey.Jan...@PolyDyne.com>
Subject RE: Tomcat and Window nonpaged pool
Date Thu, 04 Apr 2013 17:02:00 GMT
> -----Original Message-----
> From: Harris, Jeffrey E. [mailto:Jeffrey.Harris@ManTech.com]
> Sent: Thursday, April 04, 2013 10:45 AM
> To: Tomcat Users List
> Subject: RE: Tomcat and Window nonpaged pool
> 
> 
> 
> > -----Original Message-----
> > From: Jeffrey Janner [mailto:Jeffrey.Janner@PolyDyne.com]
> > Sent: Thursday, April 04, 2013 11:04 AM
> > To: 'Tomcat Users List'
> > Subject: Tomcat and Window nonpaged pool
> >
> > Tomcat 6.0.x (unsure but 33+)  with Java 1.6 and Windows 2008 Server.
> >
> > I've got a customer who is monitoring his system using the Windows
> > Performance Monitor and is concerned about Tomcat usage of the
> > nonpaged pool.  When monitoring just the Tomcat service, it shows the
> > line for the pool to slowly rise over time, with hardly ever a drop
> > that cannot be attributed to a restart of the service (I think).
> > I know that the nonpaged pool contains structures that should not be
> > paged out by Windows per this quote:
> >   "Nonpaged pool is therefore always kept present in physical memory
> > and nonpaged pool virtual memory is assigned physical memory. Common
> > system data structures stored in nonpaged pool include the kernel and
> > objects that represent processes and threads, synchronization objects
> > like mutexes, semaphores and events, references to files, which are
> > represented as file objects, and I/O request packets (IRPs), which
> > represent I/O operations."
> >
> > I am struggling with how this relates to internal workings of Tomcat
> &
> > Java.  Obviously, as more processing threads, in this case connectors
> > not executors, are opened, I would expect to see a rise in this pool
> > to support all the items it uses.  I would expect to see a drop as
> > usage dropped and connectors were returned (or are they permanent at
> 6).
> > Also, I assume processing threads for the Oracle connection pool will
> > cause this to increase as well, and should drop as the pool size drop
> > back to normal.  Any app-based threads would also cause a rise, but
> > should drop if the thread is properly terminated.
> >
> > I guess that this shows a potential memory leak somewhere, I'm just
> > wondering if there are other things I should look at that could
> > determine if this is normal behavior or indicative of a real issue.
> >
> > I do most of my Tomcat app monitoring using jconsole, jvisualvm, and
> > the Oracle OEM for looking for connection pool leaks there (not an
> > easy task).
> >
> > Any help is appreciated.
> >
> > Jeff
> 
> You might try the procedure in this URL to further isolate the issue:
> https://www.simple-talk.com/sysadmin/general/troubleshooting-nonpaged-
> and-paged-pool-errors-in-windows/
> 
> If you have the ability, you might also try disconnecting your Webapps
> and Oracle and see if simply running Tomcat by itself still displays
> the same behavior; if so, then the issue is probably Tomcat, rather
> than a Webapp or Oracle.
> 
> If you are not using the latest version of Tomcat 6.0, you might also
> want to try upgrading and see if the behavior changes, as it is
> possible there are memory leaks in earlier versions of Tomcat (some of
> the Tomcat developers can speak to that).
> 
> Jeffrey Harris

Oh, I fully expect any problems to be with our webapp and not Tomcat.
The end user should be on a version of Tomcat6 very near the latest release, at least if they
are following our usage recommendations.
Unfortunately, it's at a customer site and I have not access to it.  I'm totally dependent
on their willingness to research the issue on their end and any information about how they
are using the app vs. our other customers.  I think they are using a specific feature that
is little used by 90% of our customer base causing the issue.
I ran the same monitor against two of my hosted Tomcat instances, with several virtual hosts
each, meaning a diverse user base. It does not appear to show the pattern. However, I may
need to do a longer run to see if I replicate their results.  My results were over a 15 minute
period.  Theirs was several days.  Mine remained flat, or nearly so.  In fact, I saw a nice
little random rise and fall in the graph right around a central value for both Tomcats.  One
actually ended lower than it started.
So, I'm pretty sure it's our app and how it's being used.  Just trying to understand what
objects might be getting tossed into this pool, so I know what to go after.


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