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From Martin Schulz <>
Subject Any synchronization issues with SMP?
Date Sat, 19 Jun 2004 04:39:14 GMT
Can someone confirm that Tomcat works well on busy SMP systems (e.g. Sun 
or whether there are problems in Tomcat.

Here's what we have at our end:

We are currently performance testing our application (Tomcat 4.1.30) on 
Solaris 9,
on a V1280 system w. 8 CPUs. (SDK 1.4.2_04).  Transaction rates are 
moderate, around 30/s.

The application, after about 30-40 minutes, gets unresponsive for a 
little while (1-10 minutes),
gets back to work (for a varying period of time, but definitely under 30 
min), and then the cycle
repeats.  At half the transaction rate, the smptoms are no longer easily 

The above symptoms disappear when we use a single CPU, or a single board 
of 4 CPUs.
That scenario seems to imply synchronization problems soemwhere in the 
Java code.
The problem could not be observed in development configurations either 
(Wintel, 1-CPU Sun

The behavior is such that connections get accepted, but no response is 
sent (established connections
remain at a fixed level).   The number of connections in this state 
varies (20-70).

 From the timers we keep we learn that the service gets stuck when 
reading the input.
Once unblocked the responses get sent out rapidly again.

We have tuned the system for efficient, high-volume TCP-IP traffic.

We tried the coyote connector and the HttpConnector, both with the same 

Please respond if you can confirm or dismiss threading issues in Tomcat.
We would also be ineterested in testing approaches for such a scenario.

.I have kept system statistics for both scenarios and can provide these 
on request.

    Martin Schulz

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