This pollutes the codebase... 😞

Is there a way to provide a "default" preloading script for all packages (that will execute theseclass_exists() calls) and generate a preloading script that would load all available preloading scripts in Symfony packages? This would allow to decouple the preloading from the classes themselves.

This pollutes the codebase... disappointed

see the description why this is needed.

Is there a way to provide a "default" preloading script for all packages

That's not possible, because the list of classes that need to be preloaded is conditional: vendor/ containing a package doesn't mean in any way it's going to be used at runtime. Putting theclass_exists() calls in each files is what makes the list conditional - with the DI container in control of what is actually wired.

Yeah, I know it's necessary to fix the preload, but is this really worth it?

What I mean is, even if the preload is not perfect, it's not fundamentally broken, even if the performance is not as good as it could be.

Is getting preload working such a priority that it's worth peppering these all over the codebase?

@teohhanhui the numbers speak by themselves I think...

Theclass_exists call does not give many explicit info about why adding these lines is required for the preloading to do it's job.

Would introducing a new trait method to provide additional context via the method's name and phpdoc provide the same performance boost?

trait PreloaderTrait {publicfunctionpreload(string ...$classNames):void    {foreach($classNamesas$className) {class_exists($className);        }    }}

useSymfony\PreloaderTrait;preload(    FilesystemCache::class,    CoreExtension::class,    EscaperExtension::class,    OptimizerExtension::class,    StagingExtension::class,    ExtensionSet::class);

But once this PHP feature has matured one can safely remove these extra lines of code.

Actually not: this will remain and should become a new practice: we'll have to tell somewhere which classes are always needed by the implementations.

Here are the options:

1. in a separate file. For Symfony that'd typically mean in service definitions. Using a tag looks the most sensible, thusthis project card.
2. in the very same file as the implementation usingclass_exists() (what this PR does)
3. in the very same file as the implementation, but using a convention (e.g. docblock annotations on the classes, or a specialprivate const OPCACHE_PRELOAD = [TheClasses::class, etc.], or similar.

3. might sound nice to most, but requires coordination in the PHP ecosystem: every project needs to embrace the convention or it will not work.
2. just works everywhere, no need for any special coordination in the ecosystem
1. is a band-aid we're going to need to take over packages that won't do2. (or3. if it becomes a thing).

@rvanlaak this doesn't work, we need code thatruns - a trait doesn't "run".

Theclass_exists option seems the least maintainable, and is arguably also not PSR-1 compliant:

Files SHOULD either declare symbols (classes, functions, constants, etc.) or cause side-effects (e.g. generate output, change .ini settings, etc.) but SHOULD NOT do both.

Theclass_exists option seems the most maintainable to me. Same locality, greatest portability.

Impressive performance. at +50% it worth the maintenance cost. Hands down.

Now with this comment before all calls:
// Help opcache.preload discover always-needed symbols

👍

The comments sure are helpful

+1 for me as well.
+50% !? Almost everything is justified for +50% perfs! And few lines to declare stuff are definitely worth it.

As usual: thanks a lot!

Thanks Nicolas! This is truly impressive!

Just asking: have you tried these changes in the Symfony Demo app? Should we expect similar ~50% performance improvements? Thanks!

Thank you@nicolas-grekas.

This is the same idea as when we add list of classes that we were concatenating in one file to make things faster. Definitely worth the extra manual work.

Thanks@fabpot

@javiereguiluz no way you'll see 50% on the demo apps. It'd be surprising if it'd spend that much time doing only loading. I hope real apps do a bit more :)