PHP Performance I Everything you need to know about OpCode caches 

•Community Engineer at Engine Yard •Author of Zend PHP 5 Certification Study Guide, Sitepoints PHP Anthology: 101 Essential Tips, Tricks & Hacks & PHP Master: Write Cutting Edge Code •A contributor to Zend Framework 1 & 2, phpdoc, and PHP internals •@dshafik Davey Shafik 

What are OpCode Caches? 

What are OpCode Caches? • Performance enhancing extensions for PHP • Inject themselves into the execution life-cycle of PHP and cache as much of it as possible • Common to see a 300% speed increase with default settings! 4 

When Should I Use an OpCache? 

Always. No, really. 

Side Effects (I knew it couldn’t be that easy!) 

Cache Stampede 

Side Effects The primary side effect of using a cache is known as a cache stampede. This is where your cache expires while under heavy load. Caused by: • Restarting Server • Cache invalidation because of data edits • Newly provisioned servers being added to a cluster to help scale under load • Corruption (hardware issues) 

Which OpCode Cache 

Which OpCode Cache • There have been many caches, however till PHP 5.5 the dominant choice was the Alternative PHP Cache (APC) • With PHP 5.5, Zend open sourced it’s proprietary Zend OpCache and contributed it to the PHP project • Zend OpCache is now enabled by default with PHP 5.5+ unless disabled by --disable-all. • Zend OpCache is between 6-100% faster than APC 11 

Which OpCode Cache • PHP 5.3 or 5.4, choose between Zend OpCache and Alternative PHP Cache (APC) • PHP 5.5+, we recommend Zend OpCache • Zend OpCache can be used with PHP 5.2+ 12 

Which OpCode Cache • A second extension can be installed alongside Zend OpCache to give backwards compatibility with APC’s User Cache: APCu • APCu is APC with the OpCode Caching removed • 100% Backwards Compatible 13 

Installation 

Zend OpCache 

Installing Zend OpCache $ pecl install zendopcache-beta Add the following to your php.ini: [zendopcache] zend_extension=/full/path/to/opcache.so ; May be added by pecl opcache.memory_consumption=128 opcache.interned_strings_buffer=8 opcache.max_accelerated_files=4000 opcache.revalidate_freq=60 opcache.fast_shutdown=1 opcache.enable_cli=1 Restart PHP (php-fpm/apache) 

APC 

Installing APC $ pecl install apc-beta Add the following to your php.ini: [apc] extension=apc.so ; May be added by pecl apc.enabled=1 Restart PHP (php-fpm/apache) 

APCu (Optional) For APC User Cache Compatibility 

Installing APCu $ pecl install apcu-beta Add the following to your php.ini: [apcu] extension=apcu.so ; May be added by pecl apc.serializer=php ; See bug report for more info: http://ey.io/1aJhcOY Restart PHP (php-fpm/apache) 

Engine Yard PHP Performance Tools 

Engine Yard PHP Performance Tools • A suite of tools to aid with improving PHP performance • Open Source, Apache 2.0 License • On Github: http://github.com/engineyard/ey-php- performance-tools • Composer Compatible Package 22 

Installation Add composer.json configuration: "repositories": [ { "type": "vcs", "url": "http://github.com/engineyard/ey-php- performance-tools" } ], "require": { "php": ">=5.3.3", "engineyard/php-performance-tools": "dev-master" } Run composer update: $ composer.phar update engineyard/php-performance-tools 

Solving The Cache Stampede 

Priming The Cache 

Zend OpCache 

cache-primer 

cache-primer Create a config.php: [ 'http://ephernote.com/', 'http://ephernote.com/user/login', 'http://ephernote.com/user/register', 'http://ephernote.com/privary', // Note: this is a typo ], /* How many concurrent HTTP requests to make (requires the pecl_http extension) */ 'threads' => 3 ]; 

cache-primer Run the primer: $ /path/composer/vendor/bin/cache-primer === Cache Primer === Attempting to cache 4 URLs: Running in parallel with 3 concurrent requests ...! Cached 3 URLs in 0.6162059307098 seconds Encountered 1 errors 

cache-primer === Cache Primer === Attempting to cache 104 URLs: Running in parallel with 10 concurrent requests .......................................................... ..................!........................... Cached 103 URLs in 4.6162059307098 seconds Encountered 1 errors 

APC 

apc-primer 

Priming the Cache (APC) • Has built-in tools for priming the cache • Still requires a single HTTP request • Can cache more than just easily web accessible code • Any valid PHP can be cached, including partial view templates, global code, etc. • Use: engineyard/php-performance-tools/apc-primer 33 

apc-primer • Provides basic HTTP security • We recommend not relying on it, instead integrate it behind other authentication instead (e.g. embed it into your admin control panel) • Uses apc_compile_file() to add code to the cache • Requires a wrapper to expose via HTTP • Caches all .php and .phtml files not inside a tests directory 34 

apc-primer Create a config.php: [ 'enabled' => true, 'username' => 'admin', 'password' => 'changeme', ], /* Paths to cache (recursively) */ 'paths' => [ __DIR__ .DS. '..' .DS. '..' .DS. '..' .DS. 'config', __DIR__ .DS. '..' .DS. '..' .DS. '..' .DS. 'module', __DIR__ .DS. '..' .DS. '..' .DS. '..' .DS. 'vendor', __DIR__ .DS. '..' .DS. '..' .DS. '..' .DS. 'public', ] ]; 

apc-primer Place a simple wrapper in your web-root, e.g. /public/admin/apc-cache-primer.php

Under the Hood OR: Here be dragons! 

Execution Life-Cycle 

Execution Life-cycle: PHP vs Java 39 

Execution Lifecycle with an OpCode Cache 

Tokens & OpCodes 

The Worst Hello World, Ever sayHello("World"); ?> 

Tokenizing 

Token Name Value T_OPEN_TAG T_STRING sayHello ( T_CONSTANT_ENCAPSED_STRING "World" ) ; T_WHITESPACE T_CLOSE_TAG ?> Tokenizing 

Tokenizing • Note the difference between interpolated and non- interpolated strings. • They are both double quoted strings! • Interpolated: 4 Tokens • Non-interpolated: 1 Token • Start to see why this matters for performance: but don’t get caught up by micro-optimizations. 45 " T_ENCAPSED_AND_WHITESPACE Hello T_VARIABLE $to " T_CONSTANT_ENCAPSED_STRING "World" 

Compiling 

VLD Vulcan Logic Dumper 

VLD — Vulcan Logic Dumper • An extension to dump the compiled opcodes • Installed via PECL $ pecl install vld-beta Add the following to php.ini: extension=vld.so • Use via command line: $ php -dvld.active=1 -dvld.execute=0 48 

VLD — Vulcan Logic Dumper • Outputs, in order: • global code (main script) • global functions • class functions 49 

Understanding VLD Dumps Class Greeting: Function sayhello: filename: ./Greeting.php function name: sayHello Header compiled vars: !0 = $to number of ops: 8 

Understanding VLD Dumps (Cont.) • line: The line number in the source file • #: The opcode number • *: entry (left aligned) and exit points (right aligned), indicated by greater than symbols (>) • op: The opcode name • fetch: Details on global variable fetches (super globals, or the use of the global keyword) • ext: Extra data associated with the opcode, for example the opcode to which it should JMP • return: The location where return data from the operation is stored • operands: the operands used by the opcode (e.g. two variables to concat) 51 line # * op fetch ext return operands ---------------------------------------------------------------- 

VLD — Variables • Four types of variables 1. Exclamation point (!) are compiled variables (CVs) — these are pointers to userland variables 2. Tilde (~) are temporary variables used for temporary storage (TMP_VARs) of in-process operations 3. Dollar ($) are another type of temporary variables (VARs) which are tied to userland variables like CVs and therefore require things like refcounting. 4. Colon (:) are temporary variables used for the storage of the result of lookups in the class hashtable 52 

class Greeting -> sayHello Class Greeting: Function sayhello: compiled vars: !0 = $to line # * op fetch ext return operands ---------------------------------------------------------------- 3 0 > EXT_NOP 1 RECV !0 5 2 EXT_STMT 3 ADD_STRING ~0 'Hello+' 4 ADD_VAR ~0 ~0, !0 5 ECHO ~0 6 6 EXT_STMT 7 > RETURN null class Greeting { public function sayHello($to) { echo "Hello $to"; } } 

class Greeting -> sayHello • RECV: The function receives a value which is assigned to !0 (which represents $to) • ADD_STRING: Next we create a temporary variable identified by a ~, ~0 and assign the static string, 'Hello+', where the + represents a space • ADD_VAR: After this, we concat the contents our variable, !0 to our temporary variable, ~0 • ECHO: Then we echo that temporary variable • RETURN: Finally we return nothing as the function ends 54 

Main Script compiled vars: !0 = $greeter line # * op fetch ext return operands -------------------------------------------------------------------- 2 0 > EXT_STMT 1 NOP 9 2 EXT_STMT 3 FETCH_CLASS 4 :1 'Greeting' 4 EXT_FCALL_BEGIN 5 NEW $2 :1 6 DO_FCALL_BY_NAME 0 7 EXT_FCALL_END 8 ASSIGN !0, $2 10 9 EXT_STMT 10 INIT_METHOD_CALL !0, 'sayHello' 11 EXT_FCALL_BEGIN 12 SEND_VAL 'World' 13 DO_FCALL_BY_NAME 1 14 EXT_FCALL_END 12 15 EXT_STMT 16 > RETURN 1 $greeter = new Greeting(); $greeter->sayHello("World"); 

Main Script • FETCH_CLASS: First we lookup the class, Greeting; we store this reference in :1 • NEW: Then we instantiate an instance of the class (:1) and assign it to a VAR, $2, and • DO_FCALL_BY_NAME: call the constructor • ASSIGN: Next we assign the resulting object (in VAR $2) to our CV (!0) • INIT_METHOD_CALL: We start calling the sayHello method, and • SEND_VAL: pass in 'World' to the method, and • DO_FCALL_BY_NAME: Actually execute the method • RETURN: The script ends successfully, with an implicit return of 1. 56 

57 Resources • Zend OpCache Source Code: http://ey.io/17Qt6W9 • Zend OpCache PECL Package: http://ey.io/18h2Inp • APC Source Code: http://ey.io/18gZ9iW • APC PECL Package: http://ey.io/15JuQkp • Understanding Opcodes (Sara Golemon): http://ey.io/19q32iD • More source analysis with VLD (Derick Rethans): http://ey.io/bx0q8N http://ey.io/opcaches 

http://ey.io/opcaches Feedback & Questions: Twitter: @dshafik Email: [email protected]