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From Christopher Schultz <>
Subject Re: Non page pool issue will not go away, please help.
Date Fri, 09 Mar 2012 19:16:39 GMT
Hash: SHA1


On 3/9/12 12:19 PM, Doron Tsur wrote:
> Tomcat: 7  latest Java: 1.6.25 OS: Windows Server 2003 R2 SP2

1. What specific version of Tomcat 7?
2. 1.6.25 is not a version of Java that I know of. Real version number
   and vendor, please?

> This is a production server that uses high bandwidth. Poking
> around Poolmon.exe I was able to find that
> 1. the AfdP tag is consuming a lot of NP (Non Paged) pool.

What is "the AdfP tag"?

> 2. This is a tag concerning the windows socket driver (afd.sys).

Googling for "afd non-paged pool exhaustion" comes up with lots of
hits. Have you read them?

Many seem to suggest that certain connections are left open for a very
long time. Are you using long-lasting connections with KEEPALIVE
enabled? If so, it's possible that it could be causing this problem.

> We have many production servers running our tomcat. We have only 
> encountered this issue in two of them, those servers have the same 
> OS/Java/Tomcat installed. One server uses high bandwidth and the
> other uses much less.

Obviously, the question is: what is different about these two servers?
If this was a problem with Tomcat itself, the JVM, or even the seevice
configuration, I would expect it to happen everywhere. Given that it
doesn't happen everywhere, I would suspect something at a lower-level.
Do all servers have identical OS images on them, and are they all at
the same patch-level?

> I say tomcat because this is the process that consumes all NP pool
> (about 170MB).
> 1. Have you ever encountered this issue? 2. Do you know of any
> application level/Tomcat configuration work around to solve this
> issue?

None that I know of. Perhaps you could adjust some of the fine-grained
socket-configuration bits, but I wouldn't start fiddling without a
very good idea about what you are doing. It's even possible that
Tomcat does not support configuration of whatever specific socket bits
you need to fiddle. If that turns out to be the problem, it's fairly
easy to add configuration options.

> 3. Do you think that there is something wrong in the way Tomcat 
> interfaces with winsock?

Tomcat does not interface at all with winsock unless you are using
APR. Are you using APR? That would seem like a good thing to tell us.

> 4. Do you believe that Tomcat APR might resolve this issue?

If anything, I would say that APR might even make the problem worse.
On the other hand, it's fairly easy to try it: just drop the .dlls in
the right place and restart. As long as you haven't changed Tomcat
from the default configuration, it will use APR for your HTTP connectors.

> 5. I can't seem to download this hotfix to further investigate
> these files, they might contain a suitable version. Do you know how
> can I get them?

What hotfix are you talking about?

> When Tomcat is killed the Non Paged Pool doesn't return to the OS.

How do you "kill" Tomcat? Does the JVM process shut down entirely? If
it does, then your problem should lie elsewhere: once the process is
dead, all memory should be released. If that's not happening, there is
either a horrible bug in the OS or you are misinterpreting your

- -chris
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