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single: Performance; Byte code cache; OPcache; APC

Performance

Symfony is fast, right out of the box. However, you can make it faster if you optimize your servers and your applications as explained in the following performance checklists.

Symfony Application Checklist

These are the code and configuration changes that you can make in your Symfony application to improve its performance:

  1. Install APCu Polyfill if your server uses APC <performance-install-apcu-polyfill>
  2. Dump the service container into a single file <performance-service-container-single-file>
  3. Restrict the number of locales enabled in the application <performance-enabled-locales>

Install APCu Polyfill if your Server Uses APC

If your production server still uses the legacy APC PHP extension instead of OPcache, install the APCu Polyfill component in your application to enable compatibility with APCu PHP functions and unlock support for advanced Symfony features, such as the APCu Cache adapter.

Dump the Service Container into a Single File

Symfony compiles the service container </service_container> into multiple small files by default. Set this parameter to true to compile the entire container into a single file, which could improve performance when using "class preloading" in PHP 7.4 or newer versions:

# config/services.yaml
parameters:
    # ...
    container.dumper.inline_factories: true
<!-- config/services.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://symfony.com/schema/dic/services https://symfony.com/schema/dic/services/services-1.0.xsd">

    <parameters>
        <!-- ... -->
        <parameter key="container.dumper.inline_factories">true</parameter>
    </parameters>
</container>
// config/services.php

// ...
$container->setParameter('container.dumper.inline_factories', true);

Restrict the Number of Locales Enabled in the Application

Use the framework.translator.enabled_locales <reference-translator-enabled-locales> option to only generate the translation files actually used in your application.

Production Server Checklist

These are the changes that you can make in your production server to improve performance when running Symfony applications:

  1. Use the OPcache byte code cache <performance-use-opcache>
  2. Use the OPcache class preloading <performance-use-preloading>
  3. Configure OPcache for maximum performance <performance-configure-opcache>
  4. Don't check PHP files timestamps <performance-dont-check-timestamps>
  5. Configure the PHP realpath Cache <performance-configure-realpath-cache>
  6. Optimize Composer Autoloader <performance-optimize-composer-autoloader>

Use the OPcache Byte Code Cache

OPcache stores the compiled PHP files to avoid having to recompile them for every request. There are some byte code caches available, but as of PHP 5.5, PHP comes with OPcache built-in. For older versions, the most widely used byte code cache is APC.

Use the OPcache class preloading

Starting from PHP 7.4, OPcache can compile and load classes at start-up and make them available to all requests until the server is restarted, improving performance significantly.

During container compilation, Symfony generates the file with the list of classes to preload. The only requirement is that you need to set both container.dumper.inline_factories and container.dumper.inline_class_loader parameters to true.

The preload file path is the same as the compiled service container but with the preload suffix:

; php.ini
opcache.preload=/path/to/project/var/cache/prod/srcApp_KernelProdContainer.preload.php

Use the container.preload <dic-tags-container-preload> and container.no_preload <dic-tags-container-nopreload> service tags to define which classes should or should not be preloaded PHP.

Configure OPcache for Maximum Performance

The default OPcache configuration is not suited for Symfony applications, so it's recommended to change these settings as follows:

; php.ini
; maximum memory that OPcache can use to store compiled PHP files
opcache.memory_consumption=256

; maximum number of files that can be stored in the cache
opcache.max_accelerated_files=20000

Don't Check PHP Files Timestamps

In production servers, PHP files should never change, unless a new application version is deployed. However, by default OPcache checks if cached files have changed their contents since they were cached. This check introduces some overhead that can be avoided as follows:

; php.ini
opcache.validate_timestamps=0

After each deploy, you must empty and regenerate the cache of OPcache. Otherwise you won't see the updates made in the application. Given that in PHP, the CLI and the web processes don't share the same OPcache, you cannot clear the web server OPcache by executing some command in your terminal. These are some of the possible solutions:

  1. Restart the web server;
  2. Call the apc_clear_cache() or opcache_reset() functions via the web server (i.e. by having these in a script that you execute over the web);
  3. Use the cachetool utility to control APC and OPcache from the CLI.

Configure the PHP realpath Cache

When a relative path is transformed into its real and absolute path, PHP caches the result to improve performance. Applications that open many PHP files, such as Symfony projects, should use at least these values:

; php.ini
; maximum memory allocated to store the results
realpath_cache_size=4096K

; save the results for 10 minutes (600 seconds)
realpath_cache_ttl=600

Note

PHP disables the realpath cache when the open_basedir config option is enabled.

Optimize Composer Autoloader

The class loader used while developing the application is optimized to find new and changed classes. In production servers, PHP files should never change, unless a new application version is deployed. That's why you can optimize Composer's autoloader to scan the entire application once and build a "class map", which is a big array of the locations of all the classes and it's stored in vendor/composer/autoload_classmap.php.

Execute this command to generate the class map (and make it part of your deployment process too):

$ composer dump-autoload --no-dev --classmap-authoritative
  • --no-dev excludes the classes that are only needed in the development environment (i.e. require-dev dependencies and autoload-dev rules);
  • --classmap-authoritative creates a class map for PSR-0 and PSR-4 compatible classes used in your application and prevents Composer from scanning the file system for classes that are not found in the class map. (see: Composer's autoloader optimization).

Learn more

  • /http_cache/varnish