More tweaking for Ozblogistan

I did some minor optimisations on Ozblogistan last weekend.

I have HTTP compression enabled on the webserver (gzip, to be precise). I found out through the excellent YSlow plugin that not everything was being compressed. HTML was compressed, but not style sheets or scripts.

The nginx settings are now as follows:

gzip on;
gzip_buffers 128 8k;
gzip_types text/plain application/xml text/xml application/xml+rss text/css application/x-javascript text/javascript application/xhtml+xml;
gzip_disable "MSIE [1-6].(?!.*SV1)";

This provides a large buffer to prevent unexpected hangs. I’ve added mimetypes for javascript, RSS feeds and CSS files.

On the MySQL front, I received some advice from MySQL expert Paul Moen of Pythian.

Paul’s main advice upon looking over the MySQL settings was to increase the key_buffer variable from 8Mb. It’s currently at 96Mb. This has sped up some queries. He also advised enabling and watching MySQL’s slow query log. This helped me spot queries where indexes might speed up things, so I added a few to relevant columns which also reduced the number of slow queries. Thanks Paul.

Another change was to notice that the advice for setting connection_max in MySQL is essentially Apache/mod_php-specific. It doesn’t make sense in a FastCGI context. In FastCGI you launch a fixed number of PHP instances. The number of connections from WordPress into MySQL is limited to the number of PHP instances; so there’s no requirement to set a higher connection_max setting. This is not an optimisation per se, but it tidies things up a bit.

I double checked my PHP opcode cacher XCache and found that it was not enabled. Annoyingly, aptitude will install but not activate this for you. To actually enable it, it’s necessary to edit the php.ini file and add a line:
Somewhere in the file.

Previously I have added favicons. Watching the error log, I saw requests for apple-touch-icon.png. Apple, in their infinite wisdom, have decided to add Yet Another Assumed File to the list of things webmasters need to know about. I’ve gone through and added icons for each of the Ozblogistan sites. It was, I must tell you, tedious and time-consuming. Though Apple currently scale the images to 57×57, they will almost definitely upgrade this in future, so I’ve placed 128×128 icons for now.

Finally, I adjusted the ‘swappiness’ of the server. I configure PHP and MySQL to occupy less than the full RAM available; thus, I don’t want anything swapped out to disk. I’ve set swappiness to 0, which tells Linux to keep applications in memory at all times until it has no choice other than to swap them out.

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