Getting the most out of the PHP 7 engine - the example of

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Getting the most out of the PHP 7 engine - the example of

@nicolasgrekas

live.symfony.com

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• Born in 1995 – v7 end of 2016 • 870,000 C lines of code • Distributed leadership The PHP engine

• Since 2011 – v4 end of 2017 • PHP ^7.1 • 98 packages • 1.5B downloads Symfony

• Code infrastructure since Drupal 8 • Now at Symfony v3.4 • Deprecation policy and code • Time-based releasing process Symfony in Drupal

blog.jpauli.tech nikic.github.io

Synchronous and parallel Master Child 1 Child 2 Child n index.php index.php index.php index.php index.php index.php PHP’s memory manager insulates each scripts

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spl_autoload_register( Composer\Autoload\ClassLoader) Implement more in userland

Cache

Persistent memory pools Master Child n index.php index.php index.php Process memory Shared memory

• realpath_cache_size=1M • clearstatcache() • Compiled RegExps • OPcache What does PHP cache?

OPcache?

Steps to execute a script index.php Lexing + parsing AST opcodes Compiling Executing result

First steps are immutable index.php Lexing + parsing AST opcodes Compiling Executing result Shared memory* *append-only

Compile time optimizations AST opcodes Compiling Shared memory • Compile-time evaluation 'foo'."bar" • Dead-code elimination if (false) {…}

Compile time optimizations AST opcodes Compiling Shared memory • Compile-time evaluation 'foo'."bar" • Dead-code elimination if (false) {…} • Interned strings "foobar" len=6 hash=Ox1234 • Immutable arrays [123, ["ab" => 34]] len=2 len=1

Compile time optimizations AST opcodes Compiling Shared memory • Compile-time evaluation 'foo'."bar" • Dead-code elimination if (false) {…} • Interned strings "foobar" len=6 hash=Ox1234 • Immutable arrays [123, ["ab" => 34]] len=2 len=1

• Works for constants 'cli' === PHP_SAPI • Works for some native functions 1 === count([123]) • Needs fully-qualified identifiers namespace App; \count([123]); Compile time evaluation

namespace App; is_array($a); \is_array($a); Compile time inlining https://github.com/FriendsOfPHP/PHP-CS-Fixer/issues/3048 strlen(), is_{type}(), {type}val() casts, defined(), chr(), ord(), call_user_function(), call_user_function_array(), get_class(), get_called_class(), gettype(), count(), in_array(), array_slice(), func_num_args(), func_get_args(), function_exists(), is_callable(), extension_loaded(), constant(), dirname()

Compile time inlining https://github.com/symfony/symfony/pull/25854

Runtime-resolved identifiers are cached in the (local) opcode array Don’t « \ » all function calls Stick to the short list

Let’s split the container in one file per service PHP 7 is slow… at compiling https://github.com/symfony/symfony/pull/23678

• Loading opcodes is really fast • Still takes time and memory • « require » is also really fast opcodes move from shared memory to process’ https://github.com/symfony/symfony/pull/23678

Interned strings and immutable arrays stay in shared memory Mind opcache.interned_strings_buffer

Leveraging shared memory https://blog.blackfire.io/speeding-up-autoloading-on-php-5-6-7-0-for-everyone.html https://blog.blackfire.io/php-7-performance-improvements-immutable-arrays.html

• Shared memory is read-only $a = […]; $a[0] = 123; • Duplication happens on « write » $a = "abc"; $b = $a; $b .= "ghi"; (by the way, scalars are free, and declared properties make objects very compact) https://blog.blackfire.io/php-7-performance-improvements-ints-floats-free.html ❤ Copy-on-write

• AbstractRecursivePass • ClassLoader • VarCloner $cache[$k][$v] = [$k => $v]; Not triggering copy-on-write

What else can be slow?

Bypassing the autoloader

• gc_collect_cycles() autotriggered past 10k objects • gc_mem_caches() PHP7 memory manager is lazy • Much improved in PHP 7.3 PHP garbage collector

• Coalesce operator A ?? B vs isset(A) ? A : B https://github.com/symfony/symfony/pull/26161 • Ropes for encapsed strings "$a and $b" vs $a." and ".$b https://blog.blackfire.io/php-7-performance-improvements-encapsed-strings-optimization.html • Packed arrays (incrementing keys only) https://blog.blackfire.io/php-7-performance-improvements-packed-arrays.html • Class constants can be slow https://github.com/symfony/symfony/pull/25474 - https://github.com/twigphp/Twig/pull/2636 More goodies

• Reference mismatches are gone https://blog.blackfire.io/php-7-performance-improvements-references-mismatch.html • Copy-on-write is not triggered by (string)/(array) cast • Since PHP 7.2, « switch » statements use a hashmap • JIT is actively worked on for PHP 8 (no ETA) Even more goodies

http://www.phpbenchmarks.com/en/comparator/frameworks.html

https://rawgit.com/kocsismate/php-di-container-benchmarks/master/var/benchmark.html

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Conclusion • Wow PHP 7 • Source ideas in PHP’s C • Use only in tight loops • Never stop measuring

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Join us for contribution sprints Friday, April 13, 2018 9:00-18:00 Room: 103 Mentored Core sprint First time sprinter workshop General sprint #drupalsprint 9:00-12:00 Room: 101 9:00-18:00 Room: 104

What did you think? Locate this session at the DrupalCon Nashville website: http://nashville2018.drupal.org/schedule Take the Survey! https://www.surveymonkey.com/r/nashiville