Platinum Edition Using HTML 4, XML, and Java 1.2
(Publisher: Macmillan Computer Publishing)
Author(s): Eric Ladd
ISBN: 078971759x
Publication Date: 11/01/98

Server Performance Considerations

Real-time programs can affect server performance. SSI doesn’t bring anything new to the table in that regard.

In general, SSI programs tend to be less of a drain on the server than full-fledged CGI. SSI programs are usually small—they only have to produce text, after all—and seldom do much of any significance with files. Page hit counters that rely on generating inline graphics put far more stress on a server than an SSI counter does.

Still, a dozen—or a hundred—instances of your SSI program running at once can steal memory and processor slices needed by the server to satisfy client requests. Imagine that you are Webmaster of a large site. On each of the 250 pages for which you’re responsible, you include not one, but all the SSI examples in this chapter. Each page hit would produce seven separate processes, each of which has to jostle with the others in resource contention. In a worst-case scenario, with 100 pages being hit per minute, you would have 700 scripts running each minute, 10 or more simultaneously, at all times. This kind of load would seriously affect your server’s capability to do anything else—such as serve up pages to users who stop by to see your wonderful SSI handiwork.

You won’t find much difference among platforms either. Some SSI utilities run more efficiently in UNIX, others work better under Windows NT, and in the end, everything balances out. Programs that use the NT Registry have a distinct advantage over programs that hit the file system to save data. The Registry functions as a back-end database—always open, always ready for queries and updates. The code for handling concurrency is already loaded and running as part of the operating system, so your program can be smaller and tighter. However, pipes and forks tend to run more efficiently under some flavors of UNIX, so if your program does that sort of thing, you are better off in that environment.

Don’t pick your server operating system based on which SSI programs you plan to run. If you run into performance problems, adding RAM usually gives your server the extra headroom it needs to handle the load imposed by SSI.

	ON THE WEB For additional sites containing examples on using SSI, see:
	http://www.cgi-resources.com/Programs_and_Scripts/Perl/
	http://www.itm.com/cgicollection/index.cgi?page=1