I see, happens all the time.
> On disk caching delegates this to the OS, which is pretty good at it.
Yeah, it's just a matter of preference and convenience.
> It seems as though very few plugin authors know what O-notation means (so many nested loops), what EXPLAIN QUERY is or that tinkering and and firing up a copy on your laptop isn't really testing.
This is the real issue. I know a very few WordPress developers who have a formal technical education. While you can learn it yourself, school forces you to learn this in a great detail. In a near future, I will hopefully write on these topics, though, I need to study on this a bit more first.
Hence -- cooperative multitasking.
I've been complaining about it for years. Eg: http://clubtroppo.com.au/2008/07/10/shared-hosting-is-doomed...
I see that you are a WordPress veteran, nice to hear your opinions :)
At the point where I wrote a cron script to kill PHP every 24 hours, I realised the extra few percent weren't worth it.
Maybe it's improved, but: four times bitten, twice shy.
> Nginx stores the pages in RAM in a tree-like structure with pretty fast access times.
On disk caching delegates this to the OS, which is pretty good at it.
Badly behaved plugins and themes are not a solvable problem on Wordpress, because it's essentially a cooperative multitasking environment. One bad actor can hog all the resources and there's no way to constrain it.
It seems as though very few plugin authors know what O-notation means (so many nested loops), what EXPLAIN QUERY is or that tinkering and and firing up a copy on your laptop isn't really testing.