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From: Jeffrey Janner <Jeffrey.Janner@PolyDyne.com>
To: 'Tomcat Users List' <users@tomcat.apache.org>
Subject: RE: Tomcat and Window nonpaged pool
Thread-Topic: Tomcat and Window nonpaged pool
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Date: Thu, 4 Apr 2013 17:02:00 +0000
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> -----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
>=20
>=20
>=20
> > -----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
>=20
> 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/
>=20
> 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.
>=20
> 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).
>=20
> 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 to=
tally 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 ou=
r customer base causing the issue.
I ran the same monitor against two of my hosted Tomcat instances, with seve=
ral 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 replic=
ate their results.  My results were over a 15 minute period.  Theirs was se=
veral days.  Mine remained flat, or nearly so.  In fact, I saw a nice littl=
e random rise and fall in the graph right around a central value for both T=
omcats.  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 u=
nderstand what objects might be getting tossed into this pool, so I know wh=
at to go after.


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