OPcache Configuration Optimization

Provides production and development OPcache tuning for PHP Docker containers, including JIT and preloading.

OPcache Impact Overview

┌─────────────────────────────────────────────────────────────────┐
│                  OPCACHE PERFORMANCE IMPACT                      │
├─────────────────────────────────────────────────────────────────┤
│  Without OPcache:                                               │
│  Request → Parse → Compile → Execute → Response      ~50ms     │
│  With OPcache:                                                  │
│  Request → Execute (cached bytecode) → Response      ~15ms     │
│  With OPcache + JIT:                                            │
│  Request → Execute (native code) → Response          ~10ms     │
│  With OPcache + JIT + Preload:                                  │
│  Request → Execute (preloaded) → Response             ~5ms     │
└─────────────────────────────────────────────────────────────────┘

Production vs Development Settings

Setting	Production	Development	Purpose
opcache.enable	1	1	Enable OPcache
opcache.enable_cli	1	0	Cache for CLI scripts
opcache.memory_consumption	256	128	Shared memory (MB)
opcache.interned_strings_buffer	32	16	Interned strings (MB)
opcache.max_accelerated_files	20000	10000	Max cached files
opcache.validate_timestamps	0	1	Check file changes
opcache.revalidate_freq	0	2	Revalidation interval (s)
opcache.jit	1255	disable	JIT mode
opcache.jit_buffer_size	128M	0	JIT buffer

Memory Consumption Calculation

memory_consumption = total_php_files * avg_bytecode_size (20-50 KB per file)

  Small project (500 files):    15MB  → set 64MB
  Medium project (2000 files):  60MB  → set 128MB
  Large project (5000 files):  175MB  → set 256MB
  Enterprise (10000+ files):   350MB  → set 512MB

max_accelerated_files Calculation

PHP rounds up to the next prime from: 223, 463, 983, 1979, 3907, 7963, 16229, 32531, 65407, 130987

Total PHP Files	Set To	PHP Uses
< 200	1000	983
200-900	4000	3907
900-3800	8000	7963
3800-8000	20000	16229
8000-16000	32531	32531

JIT Configuration (PHP 8.0+)

opcache.jit = CRTO (4-digit mode)
  C: CPU optimization (0=off, 1=on)
  R: Register allocation (0=off, 1=local, 2=global)
  T: Trigger (0=first run, 3=hot counter, 5=tracing)
  O: Optimization (0=none, 5=full)

Mode	Value	Use Case
Tracing (recommended)	1255	Web applications
Function	1205	Simpler, less memory
Disabled	disable	Development, debugging

Preloading (PHP 7.4+)

<?php
// config/preload.php
$directories = [
    '/app/src/Domain/', '/app/src/Application/',
    '/app/vendor/symfony/http-kernel/',
];
foreach ($directories as $dir) {
    if (!is_dir($dir)) continue;
    $it = new RecursiveIteratorIterator(
        new RecursiveDirectoryIterator($dir, FilesystemIterator::SKIP_DOTS)
    );
    foreach ($it as $file) {
        if ($file->getExtension() === 'php') opcache_compile_file($file->getRealPath());
    }
}

Category	Preload?	Reason
Domain entities / Value objects	Yes	Loaded on every request
Framework core	Yes	Always loaded
Controllers	Maybe	Only relevant routes
Tests / Migrations	No	Not in production

Monitoring OPcache

Metric	Healthy	Action Needed
Hit rate	> 99%	< 95%: check validate_timestamps
Memory free	> 20%	< 10%: increase memory_consumption
Wasted memory	< 5%	> 10%: restart PHP-FPM
Cache full	false	true: increase max_accelerated_files

Production OPcache INI

[opcache]
opcache.enable = 1
opcache.enable_cli = 1
opcache.memory_consumption = 256
opcache.interned_strings_buffer = 32
opcache.max_accelerated_files = 20000
opcache.validate_timestamps = 0
opcache.revalidate_freq = 0
opcache.save_comments = 1
opcache.fast_shutdown = 1
opcache.jit = 1255
opcache.jit_buffer_size = 128M
opcache.preload = /app/config/preload.php
opcache.preload_user = www-data
opcache.log_verbosity_level = 1
opcache.error_log = /proc/self/fd/2

Development OPcache INI

[opcache]
opcache.enable = 1
opcache.enable_cli = 0
opcache.memory_consumption = 128
opcache.interned_strings_buffer = 16
opcache.max_accelerated_files = 10000
opcache.validate_timestamps = 1
opcache.revalidate_freq = 2
opcache.save_comments = 1
opcache.jit = disable
opcache.jit_buffer_size = 0

Dockerfile Integration

ARG APP_ENV=production
COPY docker/php/opcache-${APP_ENV}.ini /usr/local/etc/php/conf.d/opcache.ini
COPY config/preload.php /app/config/preload.php

Before/After Comparison

Metric	No OPcache	OPcache	OPcache+JIT+Preload
First request	200ms	200ms	50ms (preloaded)
Subsequent requests	200ms	15ms	5ms
Memory per worker	30MB	35MB	38MB
Throughput (req/s)	50	300	500
CPU usage	High	Medium	Low

Generation Instructions

1. Count PHP files: find /app -name "*.php" | wc -l (including vendor)
2. Calculate memory: files * 35KB, round up to nearest power of 2
3. Set max_accelerated_files: Next prime above file count
4. Configure JIT: 1255 for production, disable for development
5. Create preload script: Include domain, application, and framework core
6. Set validate_timestamps: 0 for immutable containers, 1 for development
7. Monitor: Check hit rate and memory usage after deployment