PHP OpCode? What's that?

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PHP OpCode PHP OpCode PHP OpCode What's That? What's That? What's That? Benoit Jacquemont Benoit Jacquemont Benoit Jacquemont @bjacquemont @bjacquemont @bjacquemont

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What Happen To Our Code At Execution Time?

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Lexing/Tokenizing Use the Tokenizer Extension

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Parsing To Abstract Syntax Tree

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Compilation: AST To Opcode Real value

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Opcode, Opline And Oparray opcode: instruction to execute opline: instruction with operands (0-2) and optional return assignement oparray: sequence of oplines (function, closure, main) CONCAT (0x08) T2 = CONCAT string("Hello ") CV0 ASSIGN CV0 string("World") T2 = CONCAT string("Hello ") CV0 ECHO T2 RETURN int(1)

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Execution Of The Opcode By The Zend VM

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Opcodes Are The Instructions Of The VM Virtual Processor

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PHP Version Zend Engine Version Opcodes count 4.x 1 ~130 5.x 2 167 7.x 3 172 8.x 4 207 Source: Zend/zend_vm_opcodes.h

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Why A VM? Reason #1 Performances!

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Why A VM? Reason #2 Abstraction Over The Architecture And Hardware

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Let's Dive Into Let's Dive Into Let's Dive Into Opcode! Opcode! Opcode!

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How To Display Opcode VLD Extension (from Derick Rethans) (https://pecl.php.net/package/vld) php opcache debug (since PHP 7.1) $ php -dvld.active=1 test.php $ php -d opcache.opt_debug_level=0x10000 test.php

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Hello World In Opcode! echo "Hello World !"; $_main: L0: ECHO string("Hello World!") L1: RETURN int(1)

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What About Variables? $msg = "Hello World!"; echo $msg; $_main: L0: ASSIGN CV0($msg) string("Hello World!") L1: ECHO CV0($msg) L2: RETURN int(1)

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More Complex Variables $a = 1; $b = 2; $result = $a + $b + 3; echo $result; $_main: L0: ASSIGN CV0($a) int(1) L1: ASSIGN CV1($b) int(2) L2: T5 = ADD CV0($a) CV1($b) L3: T6 = ADD T5 int(3) L4: ASSIGN CV2($result) T6 L5: ECHO CV2($result) L6: RETURN int(1)

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Control Structures

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If/Else $test = true; if ($test) { echo "Hello World!"; } else { echo "Bye World!"; } $_main: L0: ASSIGN CV0($test) bool(true) L1: JMPZ CV0($test) L4 L2: ECHO string("Hello World!") L3: JMP L5 L4: ECHO string("Bye World!") L5: RETURN int(1)

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While $test = true; while ($test) { echo "Hello World!"; $test = false; } $_main: L0: ASSIGN CV0($test) bool(true) L1: JMP L4 L2: ECHO string("Hello World!") L3: ASSIGN CV0($test) bool(false) L4: JMPNZ CV0($test) L2 L5: RETURN int(1)

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For for ($i = 0; $i < 10; $i++) { echo "Hello World!"; } $_main: L0: ASSIGN CV0($i) int(0) L1: JMP L5 L2: ECHO string("Hello World!") L3: T2 = POST_INC CV0($i) L4: FREE T2 L5: T3 = IS_SMALLER CV0($i) int(10) L6: JMPNZ T3 L2 L7: RETURN int(1)

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All Control Structures Can Be Implemented By JMP And IS_* Opcodes

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Why A VM? Reason #3 Keep PHP expressiveness while really executing a simpler language

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A Hypothetical Control Structure: Forever New Language Feature, But No Need To Change The VM forever { echo "Hello World!"; } $_main: L0: ECHO string("Hello World!") L1: JMP L0

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Internal Functions echo microtime(); $_main: L0: INIT_FCALL 0 string("microtime") L1: V0 = DO_ICALL L2: ECHO V0 L3: RETURN int(1)

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Internal Functions With Parameters $subject = "Such a nice message!"; str_replace("nice", "cool", $subject); $_main: L0: ASSIGN CV0($subject) string("Such a nice message!") L1: INIT_FCALL 3 string("str_replace") L2: SEND_VAL string("nice") 1 L3: SEND_VAL string("cool") 2 L4: SEND_VAR CV0($subject) 3 L5: DO_ICALL L6: RETURN int(1)

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User Function function hello($name) { echo "Hello $name!"; } hello("World"); $_main: L0: NOP L1: INIT_FCALL 1 string("hello") L2: SEND_VAL string("World") 1 L3: DO_UCALL L4: RETURN int(1) hello: L0: CV0($name) = RECV 1 L1: T1 = CONCAT string("Hello ") CV0($name) L2: T2 = CONCAT T1 string("!") L3: ECHO T2 L4: RETURN null

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Inheritance abstract class MyParentClass { function helloWorld() { echo "Hello World"; } } class MyChildClass extends MyParentClass{} $object = new MyChildClass(); $object->helloWorld(); $_main: L0: V4 = NEW 0 string("MyChildClass") L1: DO_FCALL L2: ASSIGN CV0($object) V4 L3: INIT_METHOD_CALL 0 CV0($object) string("helloWorld") L4: DO_FCALL L5: RETURN int(1) MyParentClass::helloWorld L0: ECHO string("Hello World") L1: RETURN null

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Opcode Cache: Monitoring $status = opcache_get_status(); $status["memory_usage"]["used_memory"] $status["memory_usage"]["free_memory"] $status["opcache_statistics"]["num_cached_keys"] $status["opcache_statistics"]["max_cached_keys"] $status["opcache_statistics"]["opcache_hit_rate"]

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Opcode Cache: Memory Settings default 64 MB increase when free_memory~0 opcache.memory_consumption

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Opcode Cache: Num Keys Settings default 2000 inc when num_cached_keys~max_cached_keys The actual value used will be the rst number in the set of prime numbers {463, 983, 1979, 3907, 7963, 16229, 32531, 65407, 130987} that is greater than or equal to the con gured value. opcache.max_accelerated_files

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The Opcode Optimizer Multipass Static Analysis To Optimize The Generated Opcode

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Optimizer Before And After Opcodes Before optimizer After optimizer $ php -d opcache.opt_debug_level=0x10000 test.php $ php -d opcache.opt_debug_level=0x20000 test.php

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Optimizer - Before And After Before After if ("foo") { echo "Foo!"; } else { echo "Not Foo!"; } L0: JMPZ string("foo") L3 L1: ECHO string("Foo!") L2: JMP L4 L3: ECHO string("Not Foo!") L4: RETURN int(1) L0: ECHO string("Foo!") L1: RETURN int(1)

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Optimizer - Before And After Before After for ($i = 0; $i < 10; $i++) { echo "Hello World!"; } L0: ASSIGN CV0($i) int(0) L1: JMP L5 L2: ECHO string("Hello World!") L3: T2 = POST_INC CV0($i) L4: FREE T2 L5: T3 = IS_SMALLER CV0($i) 10 L6: JMPNZ T3 L2 L7: RETURN int(1) L0: ASSIGN CV0($i) int(0) L1: JMP L4 L2: ECHO string("Hello World!") L3: PRE_INC CV0($i) L4: T1 = IS_SMALLER CV0($i) 10 L5: JMPNZ T1 L2 L6: RETURN int(1)

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Optimizer - Performances?

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What's Next? What's Next? What's Next?

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PHP 8 Just In Time Compilation From opcodes, generating real CPU instructions to execute them directly on the hardware

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PHP 8 JIT - Current State 5x speedup on number crunching bench.php, but... ... -0.01% performance on real world applications Main idea: allow PHP to enter areas where it's not used yet github.com/zendtech/php-src/tree/jit-dynasm/

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PHP 7.4 Preload The Main Opcache Limitation Opcache caches opcode but at le level classes and functions still need to be reloaded into the process memory

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PHP 7.4 Preload What It Will Do Permanently load in the server memory functions and classes Once loaded, these classes will be available directly, like builtins (\Exception)

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PHP 7.4 Preload How It Will Do It At server start, runs a PHP script that will load the needed le

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PHP 7.4 Preload What Can We Expect From It ZF2 Hello world app: 2x requests per second If application fully loaded, no need for autoload anymore

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Key Takeaways opcodes are the instructions of the Zend virtual CPU use opcode cache! monitor your opcode cache check out preload for PHP 7.4 (ETA end of the year)

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For More Information Nikita Popov's Blog (nikic.github.io) Julien Pauli's Blog (blog.jpauli.tech) Preload RFC PHP 7 Virtual Machine PHP's OPCache extension wiki.php.net/rfc/preload

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Thank You! Questions? @bjacquemont www.akeneo.com