PHP-FPM Configuration

Thanks for the clarification! Since the database server is separate, we can allocate more RAM to PHP-FPM because MySQL/PostgreSQL isn’t consuming memory on this server.

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🔹 Adjusted PHP-FPM Configuration for 16GB RAM & 4 Cores

Since the database is on a different server, we assume PHP-FPM, Apache/Nginx, Redis, and OS services as the main consumers of memory.

1️⃣ Determine pm.max_children

Formula:

pm.max_children = (Total Available RAM - Reserved RAM) / Average PHP Process Size

• Available RAM: 16GB
• Reserve for OS, Webserver, Cache, and Other Services: ~3GB
• PHP Process Size: ~100MB (Check with ps -ylC php-fpm8.2 --sort:rss | awk '{sum+=$8} END {print sum/NR/1024 " MB"}')

💡 Calculation:

(16GB - 3GB) / 100MB = 130

👉 Recommended: pm.max_children = 120 (keeping buffer)

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2️⃣ Set pm.start_servers

Formula:

pm.start_servers = Total CPU Cores * 2

For 4 cores:

pm.start_servers = 4 * 2 = 8

👉 If traffic is high, increase to 10-12.

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3️⃣ Set pm.min_spare_servers & pm.max_spare_servers

Formula:

pm.min_spare_servers = pm.start_servers / 2
pm.max_spare_servers = pm.start_servers * 2

For 10 start servers:

pm.min_spare_servers = 5
pm.max_spare_servers = 20

👉 Recommended:

pm.min_spare_servers = 5
pm.max_spare_servers = 20

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4️⃣ Set pm.process_idle_timeout

• For consistent traffic: Keep at 10s (default).
• For fluctuating traffic: Increase to 20-30s to avoid frequent process respawning.

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🔥 Final PHP-FPM Configuration

pm = dynamic
pm.max_children = 120
pm.start_servers = 10
pm.min_spare_servers = 5
pm.max_spare_servers = 20
pm.process_idle_timeout = 10s

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📊 Performance Monitoring

After applying the settings, restart PHP-FPM:

sudo systemctl restart php8.2-fpm

Monitor CPU/RAM usage:

htop
free -m

Check PHP-FPM process usage:

ps aux | grep php-fpm

Check logs for PHP-FPM activity:

sudo tail -f /var/log/php8.2-fpm.log

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🔄 Alternative: Use pm = ondemand for Variable Load

If your traffic is unpredictable:

pm = ondemand
pm.max_children = 120
pm.process_idle_timeout = 20s

This ensures PHP processes only run when needed, saving memory.

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🚀 These settings should provide optimal performance for your setup! Try them and monitor for any needed tweaks. Let me know if you need further adjustments! 🎯