[lgeorget]

I wonder what makes the Symfony Demo App not being faster with the JIT compiler (as shown on https://www.php.net/releases/8.0/en.php and https://susi.dev/php8-benchmark-jit-symfony).

Maybe because Symfony already caches things very efficiently/cleverly with OPCache?

[mgkimsal]

The article you link to already explains it... ?

> The point is, if you look in the announcements and comments about what the JIT does you can pretty much guess why this is kind of the expected result. The JIT compiler improves performance for CPU-intensive work (for example calculating Mandelbrots) but not so much for the "default" kind of applications. We usually don't do all that many calculations.

[lgeorget]

Yes, I read that, but that's not really what I ask. What makes JIT improve performance only for CPU-intensive work? I don't understand the connection there.

[dante_dev]

Mostly because only cpu-intensive code greatly benefits from JIT. Serving a blog (like the demo) is not much cpu-intensive.

[jashmatthews]

OO heavy code and functional heavy code can also benefit greatly from JIT compilation. The PHP8 JIT just doesn't have these optimizations yet.