IBM BS029ML Self Help Guide - Page 162
Web container, Servers, Application Servers, WebSphere_Portal, Additional Properties
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5.2.5 Web container The Web container serves to "gate" the amount of incoming HTTP requests. The larger the number of threads, the higher the number of concurrent requests are allowed to enter the Web container. At some point, however, the number of concurrent threads being processed by the Web container can overwhelm its abilities. Display Caching should be explicitly enabled for the Portal Web container. In addition, if the WebSphere Dynacache mechanism is going to be utilized by the Portal for Portlet fragment caching, the enablement of Servlet Caching is a prerequisite. To view or modify the Web container settings from the WebSphere Application Server Administrative Console, select Servers → Application Servers → WebSphere_Portal → Additional Properties → Thread Pools → Web Container. Table 5-5 shows the default and recommended settings. Table 5-5 Web container settings Parameter Enable Servlet Caching Default value Disabled Recommended value Enabled In terms of Portal performance, an increase in the maximum number of threads can offer an improvement. However, care should be taken, as increasing the value too high above the suggested optimum value of 75 threads can lead to greater %CPU and memory usage. Setting the number of minimum threads equal to the number of maximum threads does not normally offer any immediate improvement after startup. An examination of a Java thread dump will fail to show a thread count matching the minimum thread setting immediately after initialization. To view or modify the Web container settings from the WebSphere Application Server Administrative Console, select Servers → Application Servers → WebSphere_Portal → Additional Properties → Thread Pools → Web Container. Table 5-6 shows the default and recommended values. Table 5-6 Web container settings Parameter Minimum Threads Maximum Threads Is Growable Default value 10 50 Disabled Recommended value 55 75 Disabled Under no circumstances should the "Allow thread allocation beyond maximum thread size" feature be enabled. Permitting this setting can lead to runaway thread growth. The WebSphere queuing mechanism is designed to handle burst traffic, and occasional "floods" of the Web container should subsume relatively quickly in most circumstances. Attention: Our experience tells us that one commonly made mistake is that many customers increase the maximum thread pool setting beyond the recommended value in the hope of increasing performance. As this runs the risk of overwhelming the ability of a single JVM, our advice instead is to divide and conquer (D&C) by implementing WebSphere clustering. Running many JVMs, or cluster members, each with a smaller Web container, will prove beneficial when compared to a single JVM deployment with a large Web container. 148 IBM WebSphere Portal V6 Self Help Guide
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