Some of our caching systems, like the disk cache or memcached, have
significant overhead (network connections or disk I/O).
This plugin adds an additional layer of in-process cache, so we don't
need to reconnect to external cache systems when we've already
received a data item from the cache. There are some concurrency issues
here, but typically they won't be important at the level of a single
web hit.
Piwik's current default recommended JS for loading creates a <script> tag via document.write(). In addition to being generally evil, this means the browser doesn't know it's going to need piwik.js until that chunk of script gets executed... which can't happen until all scripts referenced *before* it have been loaded and executed.
The only reason for that bit of script though seems to be to pick 'http' or 'https' depending on the current page's scheme. This can be done more simply by using a protocol-relative link (eg "//piwik.status.net/piwik.js"), which the browser will resolve as appropriate. Since it's now sitting in the <script> tag, the browser's lookahead code will now see it and be able to start loading it while earlier things are parsing/executing.
May be better still to move to an asynchronous load after DOM-ready, but I'm not sure if that'll screw with the analytics code (eg, not being able to start things on the DOM-ready events since they're past).
The default full build of OpenLayers.js is 943kb as of 2.10; this gzips down to a couple hundred kb
but is still rather nasty, plus loading it off a remote host could slow things down.
Using a local copy let us cut down the size significantly by discarding unused features, and further
minification with yui-compressor shaves a bit more off. Cuts down to about 1/5 the size of the
original.
Also threw in a bundled & minified copy of the Mapstraction classes plus our usermap.js,
which covers the common case of using the default OpenLayers provider. This cuts out three
additional script loads, two of which weren't getting launched until after the mxn.js main
file got loaded.
