[Perf][RFC] make the autoload_static $classMap keys hashes

[dkarlovi]

My composer.json:

https://github.com/pimcore/demo/blob/11.x/composer.json

With some larger monolithic apps like Pimcore which include a lot of deps, autoload_static.php can grow so big it starts showing up on memory profiles.

For rough idea, on one of my Pimcore projects, it's 5.5MB and has 36k lines. On a rather simple Symfony project, it's 200KB and has 2K lines.

It seems an optimization might be possible where the FQCN in $classMap is replaced by its hash, just like $files. Since FQCN is in many cases longer than a hash (sometimes much longer), this might have a beneficial impact both on the on-disk size, but also in-memory size. I know opcache will dedup strings, but the string still needs to be kept in memory once, this will make that string shorter and should in theory improve performance.

Thoughts?

[stof]

this would force the ClassLoader to perform a hash computation for each loaded class, which will have an impact on performance.

Keys in the files list are used as a deduplication key, but the ClassLoader only loops over the variable. the classMap is used a map.

[dkarlovi]

perform a hash computation for each loaded class, which will have an impact on performance.

Correct, this is the tradeoff suggested. This might be an opt-in option if you know your classmap is gigantic so you get to pick if you want to pay with CPU or memory.

[Seldaek]

If you wanna trade runtime for memory, I'd suggest maybe not optimizing the classmap at all so you have a smaller classmap? But then it's rather io cost than cpu..

So yeah probably hashing would still be faster, but this seems like a very niche case to me. With opcache the classmap is only present once in memory and shared between fpm workers AFAIK, so that really shouldn't be a huge impact.