Troubleshooting guide
Troubleshooting Guide: PHP-FPM High Memory Usage
Use this guide to work through the most likely causes, gather useful evidence and make production-safe changes without turning a small problem into a larger outage.
PHP-FPMmemory usageWordPressWordPress infrastructureLinux
What this problem usually means
PHP-FPM can use too much memory when the pool allows too many workers, individual requests are heavy, or application code/plugins consume more RAM than expected. Increasing limits without sizing the pool can cause swapping and outages.
Production caution: Do not simply raise PHP memory_limit or max_children on a small server. That can make the site crash harder when traffic increases.
Common symptoms
- Server RAM fills during traffic spikes
- 502/504 errors appear under load
- PHP-FPM processes consume large memory each
- Swap usage increases and the site slows down
- WordPress or WordPress infrastructure becomes unstable
Common causes
- pm.max_children is too high for available RAM
- Heavy plugins, themes or long-running PHP jobs
- PHP memory_limit set high across many workers
- Slow external API calls keeping workers busy
- No object cache or inefficient database queries
- Traffic spikes from bots or crawlers
Safe first checks
These checks are intended to assist identify the direction of the issue. Always adjust paths, solution names and commands for your environment.
Show PHP-FPM processes
ps -ylC php-fpm* --sort:rss | tailCheck pool config
grep -R "pm.max_children\|memory_limit" /etc/php/*/fpm/ -nCheck memory pressure
free -m && vmstat 1 5Review slow logs if enabled
grep -R "slowlog\|request_slowlog_timeout" /etc/php/*/fpm/pool.d/ -nTypical fixes
- Calculate safe PHP-FPM worker count from real memory usage
- Use ondemand or dynamic process operations where appropriate
- Enable and review PHP-FPM slow logs
- Reduce plugin/theme load and background jobs
- Add Redis/object caching where useful
- Block abusive bot traffic at NGINX or Cloudflare
When to get assist
Get assist if the system is production-facing, customer data is involved, backup processes are uncertain, or the issue affects revenue, security hardening or uptime. We can review the logs, confirm the cause and quote a fixed-scope fix where appropriate.
Need this fixed?
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