Debugging slow sites?

[WebMonkey27]

 

Hi

 

In my new job I have inherited quite a large and complex (an in a few places badly written) PHP & MySQL website. It also handles a lot more traffic than I have been used to in my other jobs.

 

The problem I have now is chasing down performance bottlenecks and slow queries, and other glitches that cause the site to hang, be unavailable or have weird load average / memory usage spikes on the webservers and the mysql servers

 

I was wondering what other people use for sniffing out these problems, I was thinking about Zend platform, but that is looking like it might be too expensive (we are mostly advertisement funded, so margins are low despite high traffic)

 

thanks

Monkey

[0x00]

this is on my list, as for php i'm not so sure but i've been looking into bcompiler for faster loading times for large sections of code.

 

I read something somewhere about mysql benchmarking, but it wasn't just running the standard benchmark, however i can't remember what it was called. But i've just been looking into this: http://dev.mysql.com/doc/refman/5.1/en/log-files.html, and am considering the general query log. If need be i'll write a script that'll use wget every minute to call each page individually so that i can pigeon hole the results (no request should take longer than 1 min!). Hope this helps...

 

Oh for php, if you do some dfd's and sort of identify the big blocks you could then setup your own benchmarking echoing microtime() string's (http://uk3.php.net/manual/en/function.microtime.php).