minor #24872 [DI] Add "container.hot_path" tag to flag the hot path and inline related services (nicolas-grekas)

This PR was merged into the 3.4 branch.

Discussion
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[DI] Add "container.hot_path" tag to flag the hot path and inline related services

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

This PR is the result of my quest to squeeze some performance out of 3.4/4.0.

It builds on two ideas:
- a new `container.inline` tag that identifies the services that are *always* needed. This tag is only applied to a very short list of bootstrapping services (`router`, `event_dispatcher`, `http_kernel` and `request_stack` only). Then, it is propagated to all dependencies of these services, with a special case for event listeners, where only listed events are propagated to their related listeners.
- replacing the PHP autoloader by plain inlined `require_once` in generated service factories, with the benefit of completely bypassing the autoloader for services and their class hierarchy.

The end result is significant, even on a simple Hello World.
Here is the Blackfire profile, results are consistent with `ab` benchmarks:

https://blackfire.io/profiles/compare/b5fa5ef0-755c-4967-b990-572305f8f381/graph

![capture du 2017-11-08 16-54-28](https://user-images.githubusercontent.com/243674/32558666-a3f439b2-c4a5-11e7-83a3-db588c3e21e5.png)

Commits
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f7cb559a06 [DI] Add "container.hot_path" tag to flag the hot path and inline related services

Author: fabpot

DependencyInjection/Compiler/UnusedTagsPass.php

@@ -24,6 +24,7 @@ class UnusedTagsPass implements CompilerPassInterface
     private $whitelist = array(
         'cache.pool.clearer',
         'console.command',
+        'container.hot_path',
         'container.service_locator',
         'container.service_subscriber',
         'controller.service_arguments',

FrameworkBundle.php

@@ -43,6 +43,7 @@
 use Symfony\Component\Form\DependencyInjection\FormPass;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpKernel\Bundle\Bundle;
+use Symfony\Component\HttpKernel\KernelEvents;
 use Symfony\Component\Config\Resource\ClassExistenceResource;
 use Symfony\Component\Translation\DependencyInjection\TranslationDumperPass;
 use Symfony\Component\Translation\DependencyInjection\TranslationExtractorPass;
@@ -83,14 +84,22 @@ public function build(ContainerBuilder $container)
     {
         parent::build($container);
 
+        $hotPathEvents = array(
+            KernelEvents::REQUEST,
+            KernelEvents::CONTROLLER,
+            KernelEvents::CONTROLLER_ARGUMENTS,
+            KernelEvents::RESPONSE,
+            KernelEvents::FINISH_REQUEST,
+        );
+
         $container->addCompilerPass(new LoggerPass(), PassConfig::TYPE_BEFORE_OPTIMIZATION, -32);
         $container->addCompilerPass(new RegisterControllerArgumentLocatorsPass());
         $container->addCompilerPass(new RemoveEmptyControllerArgumentLocatorsPass(), PassConfig::TYPE_BEFORE_REMOVING);
         $container->addCompilerPass(new RoutingResolverPass());
         $container->addCompilerPass(new ProfilerPass());
         // must be registered before removing private services as some might be listeners/subscribers
         // but as late as possible to get resolved parameters
-        $container->addCompilerPass(new RegisterListenersPass(), PassConfig::TYPE_BEFORE_REMOVING);
+        $container->addCompilerPass((new RegisterListenersPass())->setHotPathEvents($hotPathEvents), PassConfig::TYPE_BEFORE_REMOVING);
         $container->addCompilerPass(new TemplatingPass());
         $this->addCompilerPassIfExists($container, AddConstraintValidatorsPass::class, PassConfig::TYPE_BEFORE_REMOVING);
         $container->addCompilerPass(new AddAnnotationsCachedReaderPass(), PassConfig::TYPE_BEFORE_REMOVING);

Resources/config/services.xml

@@ -9,6 +9,7 @@
 
         <service id="event_dispatcher" class="Symfony\Component\EventDispatcher\ContainerAwareEventDispatcher" public="true">
             <argument type="service" id="service_container" />
+            <tag name="container.hot_path" />
         </service>
         <service id="Symfony\Component\EventDispatcher\EventDispatcherInterface" alias="event_dispatcher" />
 
@@ -17,6 +18,7 @@
             <argument type="service" id="controller_resolver" />
             <argument type="service" id="request_stack" />
             <argument type="service" id="argument_resolver" />
+            <tag name="container.hot_path" />
         </service>
         <service id="Symfony\Component\HttpKernel\HttpKernelInterface" alias="http_kernel" />
 

composer.json

@@ -22,7 +22,7 @@
         "symfony/class-loader": "~3.2",
         "symfony/dependency-injection": "~3.4|~4.0",
         "symfony/config": "~3.4|~4.0",
-        "symfony/event-dispatcher": "^3.3.1|~4.0",
+        "symfony/event-dispatcher": "^3.4-beta4|~4.0-beta4",
         "symfony/http-foundation": "^3.3.11|~4.0",
         "symfony/http-kernel": "~3.4|~4.0",
         "symfony/polyfill-mbstring": "~1.0",