Apache compression making site seem sluggish?

[trevordixon]

I'm rebuilding a site that was originally coded in C and runs extremely quickly. Now I'm trying to optimize the new PHP/MySQL site and pages aren't appearing fast enough in the browser. The old pages seem to appear in Firefox 3 to 5 seconds quicker than the new pages do.

The old pages appear much more quickly than my new PHP pages, but I don't think it's because of the PHP code itself. I ran the Microsoft Web Application stress tool on the old site and on my new site, and the average response time for my new pages was approximately .7 seconds. The old page's response time was about .3 seconds. A half a second difference in server response time shouldn't make my site seem that sluggish, should it?

It also said that the total download amount for my new pages was like 7kb even though it's closer to 35kb, but the download size for the old page was 34kb--the actual size of the page. I think that means the new site is getting compressed before served (the old site is running on a shared host and the old site is on a dedicated server that a friend of mine maintains).

Is it possible that the old site isn't getting compressed first and thus it can start being shown before it's entirely downloaded while the compressed pages have to be downloaded completely then decompressed before the visitor can see anything in the browser?

Thanks in advance for your wisdom and advice,
Trevor

[edited by: jdMorgan at 2:34 am (utc) on July 4, 2007]
[edit reason] No URLs, please. See TOS. [/edit]

[jdMorgan]

You should consider caching the compressed pages, both for purposes of identifying the current bottleneck, and also as a long-term solution. You can accomplish this in many ways, from mod_proxy to a 'manual' solution using a script, mod_rewrite, and a cron job, but the end result is the same; A page only needs to be re-compressed when it changes.

For the current problem, serving up a cached compressed page would answer the question of whether it is a server-side compression-time issue or an initial browser rendering delay issue.

Also look at the configured compression level; If set too high, CPU time and compression delay goes way up, but with little gain in file compression.

Jim