I had my site slow to a halt today when the memory footprint of PHP went crazy. So I've been checking out the impact of different plugins running, creating a spreadsheet to determine memory usage and page load times as I added each plugin in turn. I did this for the 30 main plugins I'm using.
There are another 20 or so smaller utility plugins I have still to activate, but before my memory usage goes crazy I'm wondering what tips anyone has to reduce their impact, for a Multisite network running Buddypress.
BuddyPress, bbPress, MarketPress, various media and social plugins have quite an impact. Would it make sense to only network activate those tools that are used across the whole network? Does this reduce the general footprint when browsing 'lighter' sites? Then just enable plugins in sites when needed (or upgraded to Pro)?
Or are plugins always in memory that are activated at least on one site on the server?