all things can not be cached heavily. And even for things that can you still need to regenerate the cached data to some degree. Code that is ten times slower will require 10 times more hardware even if you cache. The cache only makes the number you're multiplying by 10 smaller.
This is why Facebook spent so much time and energy working on HipHop. I'm sure they have many caching layers as well, but caching only gets you so far -- eventually you have to look at your code.
interesting how things come and go and come back. Some years ago it was Yahoo moving their web layer from C++ based templating to something of more higher level, now Facebook [implicitly] moves their layer down to C++ ...
HipHop engineer, here. Unless you consider programming in C++ to be [implicitly] programming in machine language, this doesn't make a lot of sense. Our application engineers write real, no-fooling PHP, at exactly the same level of abstraction as they always have. They usually don't bother compiling it either, instead iterating using our interpreter which behaves more like a drop-in replacement for Apache+Zend.
I've been looking at HipHop lately -- can you give me a general idea of how much you have to work around HipHop for it to still compile? I know that the references I've seen to it have all indicated that it might choke on certain types of code, but I'm curious as to how mindful you have to be?
If you stick to the brightly lit parts of the language, things will work. The Facebook codebase was and is enormous, so the vast majority of PHP has to work as advertised. The one big thing that's ruled out is eval, but other wacky PHP tricks ($f(), $C::staticMethod, $obj->$methodName(), foreach order, etc.) work. Outside of eval, you have to go out of your way to break it.
That said, it's a young project, and things can be a bit rocky. Including compilation in your deployment process is also a pain; do not kid yourself about that. It's kind of "industrial strength" in general; unless you care about how many PHP requests you can squeeze out of a unit of hardware, HipHop doesn't have much to offer.
This is logically just nonsense. So the php compiles to C++ now? The devs still write in php, they don't move to another language (well they use a somewhat restricted set of php, but a lot of places do that anyway for various reasons).
It is as silly as saying anyone programming in a JVM language is just programming in Java, or anyone using a language which compiles to machine code is just using assembler. (implicitly of course!)
It seems a lot of people over look ESI support in Varnish. Proper use of ESI in pages that have content sections that update at different intervals can make a large impact.
