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6. Performance Analysis > Using analysis.cgi to Find a Bottleneck

Using analysis.cgi to Find a Bottleneck

A simple first step in diagnosing a performance problem is to break down performance into five categories: DNS lookup time, connection setup time, server silence, transmission time, and connection close time. These steps always happen in this order. I’ve written a tool to automatically time each of these five steps and to generate a graph of the results and some advice. I call it analysis.cgi and it can be run from my home page, http://patrick.net/. Simply enter a URL and it will try to graph the breakdown of these components for that URL. Figure 6-1 shows an example output graph for my own home page. Here is the advice:

analysis.cgi graph for patrick.net

Figure 6-1. analysis.cgi graph for patrick.net

advice for http://patrick.net/


I spent a cumulative 0.4052 seconds resolving hostnames. No problem with DNS.

It took a cumulative total of 0.0650 seconds to set up the connections to download 
your content. The average time to connect was 0.0325 seconds. The latency to make a 
connection to your site was OK. I spent 0.0012 seconds closing the socket.

There was a cumulative 0.1334 seconds of server silence. The average period of server 
silence was 0.0667 seconds. Your server is using HTTP 1.1, which has better 
performance than HTTP 1.0. Good.


Your content was a total of 4984 bytes, including headers. It would take at least 0.
7120 seconds to download the content over a 56 Kbps modem. It would take at least....



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