The effect of running requests as processes rather than as shared threads is significant. CGI applications have been demonstrated to use three to five times more processor time and memory space. CGI applications have also been demonstrated to be three to five times slower than equivalent ISAPI DLLs on the same server and network.
If you run CGI or ISAPI applications, or plan to, you need to know how to monitor their overhead. You must also build in sufficient excess capacity to accommodate their use. The following sections explain how to monitor CGI and ISAPI applications, and how to use simulation tools to help predict processor and memory requirements for CGI and ISAPI.