How to make WebLogic use all the processors on a multi processor machine

In common scenarios, WebLogic (and thus Java) should be able to use all the available processors in the server where it's running. WebLogic has a pool of request processing threads and when requests are arriving concurrently, they are handled concurrently. If the server has multiple processors those should be then used by Java threads.

If the Java web application running in WebLogic is using SingleThreadModel in its servlet(s), no two threads can execute the servlet concurrently and thus you could see only one CPU at work there. This model is not recommended and I guess not much used anyway.

I've heard some people complaining that they cannot get their Java app servers to use more than 1 CPU when running a virtual machine OS, like VMWare, even when they have dedicated more than one CPU for the VM. I have no idea what was the reason for this strange behavior then.

Maybe you should try to hit some very simple JSP page with concurrent requests and see if more than 1 CPU is being used. If this works, the problem is in your application.

Oh come on, you really don't need to configure a clustered environment to be able to use multiple processors in a Java application! All Java app servers handle request processing with concurrent threads by default. Only way to circumvent this is to either use single-threaded servlet model (a developer decision, although mostly bad one) or to limit request processing threads to 1 (=ridiculous).

Kaitsu 2009-08-21 20:53:56

No indication about single thread model, so I'm assuming that the questioner wasn't so foolish as to go that way. Since the WebLogic docs themselves refer to special handling needed for multi-processor machines, the original question indicates that multi-processors are not used out of the box, and multi-threads are not the same as multi-processors, I'll stand by my original answer until better information comes along.

duffymo 2009-08-22 01:18:25

@duffymo: Sorry, if my comment sounded rude. I just wanted to make my point clear. :)

Kaitsu 2009-08-22 09:23:10

No worries, Kaitsu. Change your mind about the down vote then, or does that still stand as well?

duffymo 2009-08-22 11:13:15

Don't you mean http://download.oracle.com/docs/cd/E13222_01/wls/docs81/perform/WLSTuning.html or http://download.oracle.com/docs/cd/E12840_01/wls/docs103/perform/WLSTuning.html

Pascal Thivent 2009-10-07 20:53:46

"I've heard some people complaining that they cannot get their Java app servers to use more than 1 CPU when running a virtual machine OS, like VMWare, even when they have dedicated more than one CPU for the VM. I have no idea what was the reason for this strange behavior then." - kinda like the original poster, right? This is what you call a helpful answer? Please.

duffymo 2009-08-22 00:44:18

@duffymo: Well, the part that you quoted from my answer was just an addition to the actual answer, which at least contained something concrete compared to your suggestion to start reading WebLogic docs on how to start clustering WL. That's like shooting a fly with a big cannon when the problem is just to get a an application to run with multiple processors, which by the way, is very common in Java web applications. Peace.

Kaitsu 2009-08-22 09:21:46

@Kaitsu, BEA disagrees with you, and the data posted by the questioner says that your way isn't working. That's the whole reason for the question. You keep insisting that it simply works, and that the application that you haven't seen is at fault, but the data doesn't support your view. I fully understand that Java web apps are multi-threaded; no disagreement there. But it's one JVM per CPU for WebLogic and JBOSS and other Java EE app servers that I use. I believe it's more than multi-threading. It's shared state for stateful EJBs, sessions, load balancing, etc.

duffymo 2009-08-22 11:15:43

@duffymo: It surely isn't one JVM per CPU for WebLogic (or any other Java EE server for that matter), or can you show us any proof of that? Your link to the WebLogic documentation didn't say anything about CPUs. If one JVM per CPU would be the case, you would need 4 JVMs to fully utilize a 4-CPU server and that just doesn't make any sense. I have used and built plenty of Java web applications and witnessed with my own eyes how beautifully a Java server process utilizes all the CPUs in the system.

Kaitsu 2009-08-22 20:12:55

Some Resin users seem to experience same kind of problems like reported here, but Resin creator Scott Ferguson claims that they cannot reproduce it and it shouldn't work that way. See more here: http://bugs.caucho.com/view.php?id=3465

Kaitsu 2009-08-22 20:16:29

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How to make WebLogic use all the processors on a multi processor machine

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