Web Performance Tuning

Chapter 4. Case Studies

Example Performance Problems, Diagnoses, and Solutions

Here are some hypothetical cases of web performance problems and their solutions. Any resemblance to situations you recognize is coincidental.

Not Enough Memory on Server

The Custom Pasta Corporation routinely gets most of its orders via its web site on Tuesday evenings. Unfortunately, the performance of its site also slows to a crawl at that same time every week. The webmaster is asked to check out the server configuration and fix the problem.

She figures, first of all, that the server is being overloaded somehow, because many clients have reported this problem, and there is no obvious reason for a surge in overall Internet traffic on Tuesday evenings. On Tuesday evening, she tries some tests. First, she connects from a client machine she knows to have good performance and places a test order for pasta. It does indeed take a very long time to get back to her with an acknowledgment page. So even a good client on a LAN connection to the web server has problems.

Perhaps the problem is that the LAN is overloaded. The webmaster logs in to the web server itself, a Sun Ultra, and runs the snoop utility. She stops the output and looks through it. There are a few HTTP requests and replies going back and forth, but they don’t seem excessive, and there is not a particularly high number of TCP retransmits. There is no NFS traffic because all of the content is on this machine’s local disk. The netstat -i command ...