Preload services

[gnugat]

Instantiate all services in the Dependency Injection Container.

Stateless (shared) services in the Dependency Injection Container will be instantiated once by the first Request that require them, and then their instance will be reused in all other Requests.

This also allows to "warm up" part of autoloading.

[marcj]

To be honest, I'm not a friend of instantiating all services. Some heavy instances I need only in few requests or even in commands only and shouldn't be instantiated on every request. If this brings a heavy perf boost in first connections we should think about an option to triggers this. What gain did you get with this?

[gnugat]

I get your point: without this "preloading", most services will be eventually "loaded" anyway (apart from command specific services), so it might not seem like a big improvement.

I'll come up with some PHP-PM benchmarks soon, but for PHPFastCGI I got the following results (around 6% faster):

• Requests per second: from 1115.87#/sec to 1185.59#/sec
• Time per request: from 8.962ms to 8.435ms ()
• Time per request (across all concurrent requests): from 0.896ms to 0.843ms

[marcj]

Alright, then let us wait for benchmarks in php-pm and if it's worth we should enable it with an option to disable it (for example if you have an application with heavy services and too many)

[gnugat]

Hey, I've done some benchmarking and there a no noticeable differences. That's probably because PHP PM runs a preliminary request when starting the kernel so autoloading and services for the homepage are already loaded.

After some though, I agree with you: autoloading and services would be loaded eventually and kept alive so it wouldn't impact much performances of a live application. Regarding benchmarks, where the first request might be slower and impact the average result, since we run a preliminary request we get rid of this risk.

I'll close this PR. It's been interesting to investigate, at least now we have an answer for future similar questions.