✅ Quick Steps to Resolve
1. Check Average Memory Used per PHP-FPM Process
Run:
ps --no-headers -o rss -C php-fpm8.2 | awk '{sum+=$1} END {print sum/NR/1024 " MiB per process"}'
➡️ Result: e.g., 96.81 MiB per process
2. Estimate Safe Memory for PHP-FPM
- Total RAM: 8 GiB = 8192 MiB
- Reserve for OS & Others: ~1.5 GiB
- Available for PHP-FPM:
8192 - 1536 = 6656 MiB - Memory per PHP Process: ~90–100 MiB (rounded)
➡️ 6656 / 95 ≈ 70
✅ Set pm.max_children = 70
3. Edit PHP-FPM Pool Config
Edit the file:
sudo nano /etc/php/8.2/fpm/pool.d/www.conf
Change/add these lines:
pm = dynamic
pm.max_children = 70
pm.start_servers = 8
pm.min_spare_servers = 4
pm.max_spare_servers = 12
pm.max_requests = 500
4. Reload PHP-FPM
sudo systemctl reload php8.2-fpm
This setup prevents your server from hitting memory limits and triggering the OOM killer while keeping PHP responsive under load.