Low Memory Configuration

The WordPress container supports running in memory-constrained environments such as small VPS instances or containers with limited RAM. This guide covers the settings needed to optimize for low-memory deployments.

Minimum Memory Requirements

WordPress requires a minimum of 64MB PHP memory to function properly. Settings below 64M (such as 32M) will cause HTTP 500 errors with the message "This page isn’t working" - this is a PHP out-of-memory condition, not a container failure. When this happens, increase PHP_MEMORY_LIMIT to at least 64M.

info

For Apache MPM-specific tuning, see Apache MPM Configuration.

Low Memory Mode

The APACHE_LOW_MEMORY_MODE environment variable enables automatic tuning of Apache MPM settings for constrained RAM environments.

wordpress:
  image: ghcr.io/supanadit/containers/wordpress-apache:6.9-r3
  environment:
    APACHE_LOW_MEMORY_MODE: "true"

When enabled, the following settings are automatically applied based on your APACHE_MPM selection:

Event MPM (Default, Most Memory-Efficient)

Setting	Low Memory Default	Description
StartServers	1	Initial server processes
MinSpareThreads	10	Minimum idle threads
MaxSpareThreads	25	Maximum idle threads
ThreadsPerChild	10	Threads per server process
MaxRequestWorkers	50	Maximum concurrent requests
MaxConnectionsPerChild	100	Connections before process restart

Worker MPM

Setting	Low Memory Default	Description
StartServers	1	Initial server processes
MinSpareThreads	10	Minimum idle threads
MaxSpareThreads	25	Maximum idle threads
ThreadsPerChild	10	Threads per server process
MaxRequestWorkers	50	Maximum concurrent requests
MaxConnectionsPerChild	100	Connections before process restart

Prefork MPM (Thread-Unsafe PHP, Less Efficient)

Setting	Low Memory Default	Description
StartServers	2	Initial server processes
MinSpareServers	1	Minimum idle servers
MaxSpareServers	3	Maximum idle servers
MaxRequestWorkers	10	Maximum concurrent requests
MaxConnectionsPerChild	100	Connections before process restart

warning

Prefork MPM is less memory-efficient than Event/Worker because each Apache process loads its own PHP interpreter. Use Event or Worker MPM for better memory efficiency.

Memory Optimization Checklist

For deployments under 256MB RAM:

1. Use Event MPM (default, already optimal)
2. Enable Low Memory Mode
3. Reduce OPcache memory or disable if needed
4. Set explicit PHP memory limit

Example Configurations

256MB RAM Target

wordpress:
  image: ghcr.io/supanadit/containers/wordpress-apache:6.9-r3
  restart: always
  environment:
    WORDPRESS_DB_HOST: mariadb:3306
    WORDPRESS_DB_USER: root
    WORDPRESS_DB_PASSWORD: secret
    WORDPRESS_DB_NAME: wordpress
    WORDPRESS_FS_METHOD: "direct"

    # Use Event MPM (default, most memory-efficient)
    APACHE_MPM: event

    # Enable low memory mode
    APACHE_LOW_MEMORY_MODE: "true"

    # PHP settings
    PHP_MEMORY_LIMIT: 64M
    PHP_OPCACHE_MEMORY: 32
    PHP_OPCACHE_MAX_ACCELERATED_FILES: 200
  volumes:
    - ./.data/wordpress:/content

128MB RAM Target (OPcache Disabled)

Performance Impact

At 128MB container memory with OPcache disabled, WordPress will be extremely slow because every PHP request requires full script recompilation. This configuration should only be used for testing or development, not production sites with traffic.

wordpress:
  image: ghcr.io/supanadit/containers/wordpress-apache:6.9-r3
  restart: always
  environment:
    WORDPRESS_DB_HOST: mariadb:3306
    WORDPRESS_DB_USER: root
    WORDPRESS_DB_PASSWORD: secret
    WORDPRESS_DB_NAME: wordpress
    WORDPRESS_FS_METHOD: "direct"

    # Use Event MPM
    APACHE_MPM: event

    # Enable low memory mode
    APACHE_LOW_MEMORY_MODE: "true"

    # Disable OPcache for minimal memory usage
    PHP_OPCACHE_ENABLE: "false"

    # 64M is the minimum viable PHP memory for WordPress
    PHP_MEMORY_LIMIT: 64M
  volumes:
    - ./.data/wordpress:/content

64MB RAM Target (Absolute Minimum, Not Recommended)

This is the absolute minimum configuration. WordPress will barely function:

• No OPcache (disabled)
• No plugins or themes beyond defaults
• Very slow performance
• Frequent out-of-memory errors under any load

wordpress:
  image: ghcr.io/supanadit/containers/wordpress-apache:6.9-r3
  restart: always
  environment:
    WORDPRESS_DB_HOST: mariadb:3306
    WORDPRESS_DB_USER: root
    WORDPRESS_DB_PASSWORD: secret
    WORDPRESS_DB_NAME: wordpress
    WORDPRESS_FS_METHOD: "direct"

    APACHE_MPM: event
    APACHE_LOW_MEMORY_MODE: "true"
    PHP_OPCACHE_ENABLE: "false"
    PHP_MEMORY_LIMIT: 64M
  volumes:
    - ./.data/wordpress:/content

Troubleshooting

HTTP 500 Error with Low Memory Settings

If you see "This page isn’t working" (HTTP 500) error:

1. This is NOT a container failure - it's PHP running out of memory
2. Increase PHP_MEMORY_LIMIT from 32M/64M to at least 128M
3. Check container logs: docker logs <container_name>
4. If running in a memory-constrained environment, increase container memory limit

Symptoms of PHP Memory Exhaustion

Symptom	Cause	Solution
HTTP 500 "This page isn't working"	PHP memory limit too low	Increase PHP_MEMORY_LIMIT to 64M+
"Allowed memory size of X bytes exhausted" in logs	WordPress needs more PHP memory	Increase PHP_MEMORY_LIMIT
Site loads but admin is broken	Admin requires more memory	Increase PHP_MEMORY_LIMIT to 128M+

Overriding Individual Settings

You can override specific MPM settings while still using APACHE_LOW_MEMORY_MODE for the others:

wordpress:
  image: ghcr.io/supanadit/containers/wordpress-apache:6.9-r3
  environment:
    APACHE_MPM: event
    APACHE_LOW_MEMORY_MODE: "true"
    # Override specific setting
    APACHE_MPM_EVENT_MAX_REQUEST_WORKERS: 30