This is a new transparent technology that eliminates overhead of PHP class inheritance.
PHP classes are compiled and cached (by opcahce) separately, however their "linking" was done at run-time - on each request. The process of "linking" may involve a number of compatibility checks and borrowing methods/properties/constants form parent and traits. This takes significant time, but the result is the same on each request.
Inheritance Cache performs "linking" for unique set of all the depending classes (parent, interfaces, traits, property types, method types involved into compatibility checks) once and stores result in opcache shared memory. As a part of the this patch, I removed limitations for immutable classes (unresolved constants, typed properties and covariant type checks). So now all classes stored in opcache are "immutable". They may be lazily loaded into process memory, if necessary, but this usually occurs just once (on first linking).
The patch shows 8% improvement on Symphony "Hello World" app.
Due to ASLR restrictions, preloading on Windows does not work with
any code that has preloading dependencies on internal classes.
This effectively makes it unusable for any non-trivial codebase.
Instead of pretending like preloading is going to work, only to
make people realize that it really doesn't once they get beyond
a dummy example, we disable support for preloading on Windows
entirely.
Closes GH-4999.
GCC complained about potentially uninitialized __orig_bailout,
even though the variable has an initializer. This warning was
quite persistent, I was only able to avoid it by using a separate
function.
Am I missing something?
During preloading, check that all classes that have been included
as part of the preload script itself (rather than through opcache_compile_file)
can actually be preloaded, i.e. satisfy Windows restrictions, have
resolved initializers and resolved property types. When resolving
initializers and property types, also autoload additional classes.
Because of this, the resolution runs in a loop.
Max Semenik