Memory Management
# Memory Management in MediaWiki 1.40
This article details memory management considerations for running a MediaWiki 1.40 installation. Proper configuration is crucial for performance and stability, particularly with larger wikis or high traffic. This guide is aimed at system administrators and server engineers responsible for maintaining a MediaWiki instance.
Understanding MediaWiki's Memory Usage
MediaWiki, built on PHP, relies heavily on the server's memory (RAM). Several factors contribute to its memory footprint:
- PHP Memory Limit: The maximum amount of memory a single PHP script can consume. This is the primary control point.
- Database Cache: The database server (typically MySQL/MariaDB or PostgreSQL) uses memory for caching query results.
- OPcache: PHP's built-in opcode cache stores precompiled script bytecode, reducing parsing overhead and memory usage over time.
- Extensions: Installed PHP extensions consume memory.
- Wiki Content: The size and complexity of wiki pages, especially those with many images or complex templates (though we avoid templates here), directly impact memory usage.
- User Sessions: Each active user session consumes memory.
- PHP Configuration
- MySQL Configuration
- PostgreSQL Configuration
- Server Hardware
- Performance Tuning
- Caching Strategies
- Database Maintenance
- Troubleshooting Common Errors
- Web Server Configuration
- Load Balancing
- System Monitoring
- Security Best Practices
- Extension Installation
- MediaWiki Scalability
- Database Schema
- Telegram: @powervps Servers at a discounted price
PHP Memory Limit Configuration
The PHP memory limit is the most immediate setting to adjust. It's configured in the `php.ini` file. Increasing this value can resolve "out of memory" errors, but it's not a limitless solution. Excessive allocation can lead to server instability.
Here's a table showing common PHP memory limit settings and their implications:
| PHP Memory Limit | Recommended Use Case | Potential Issues |
|---|---|---|
| 128M | Small wikis (under 10,000 pages), low traffic | May encounter errors during complex operations (e.g., large edits, report generation). |
| 256M | Medium-sized wikis (10,000 - 100,000 pages), moderate traffic | Generally sufficient for most operations, but may need adjustment for very large pages. |
| 512M | Large wikis (over 100,000 pages), high traffic, complex extensions | Requires sufficient server RAM; excessive allocation can starve other processes. |
| 1G+ | Extremely large wikis, very high traffic, resource-intensive extensions | Requires significant server RAM; careful monitoring is essential. |
To modify the PHP memory limit, edit your `php.ini` file (location varies depending on your operating system and PHP installation) and find the `memory_limit` directive. For example:
``` memory_limit = 256M ```
After changing `php.ini`, you *must* restart your web server (e.g., Apache or Nginx) for the changes to take effect. Verify the setting using `phpinfo()` by creating a file named `info.php` containing `` and accessing it through your web browser. Search for "memory_limit" in the output. See PHP Configuration for more information.
Database Server Memory Allocation
The database server (MySQL/MariaDB or PostgreSQL) requires sufficient memory for efficient operation. The optimal configuration depends on the size of your wiki's database and the number of concurrent connections.
Here's a breakdown of key MySQL/MariaDB memory parameters:
| Parameter | Description | Default Value (approx.) | Recommended Adjustment |
|---|---|---|---|
| `innodb_buffer_pool_size` | The size of the buffer pool used to cache InnoDB data and indexes. | 128M | Allocate 50-80% of available RAM to this, if using InnoDB. |
| `key_buffer_size` | The size of the buffer used to cache MyISAM index blocks. | 8M | If using MyISAM tables, increase this value. Otherwise, leave at default. |
| `query_cache_size` | The size of the query cache, which stores the results of SELECT queries. (Deprecated in newer versions) | 0 | Consider disabling in modern MariaDB/MySQL versions. |
| `max_connections` | The maximum number of concurrent connections to the database server. | 151 | Adjust based on expected concurrent users and application load. |
PostgreSQL also has important memory settings. Refer to the PostgreSQL Configuration article for details. Monitoring database performance with tools like `mysqltuner.pl` (for MySQL/MariaDB) or `pg_stat_statements` (for PostgreSQL) is crucial for identifying bottlenecks.
OPcache Configuration
OPcache significantly improves PHP performance by caching precompiled bytecode. Proper configuration is essential.
| Parameter | Description | Recommended Value |
|---|---|---|
| `opcache.enable` | Enables or disables OPcache. | 1 (Enabled) |
| `opcache.memory_consumption` | The amount of memory allocated to OPcache. | 128M - 256M (adjust based on wiki size) |
| `opcache.validate_timestamps` | Controls whether OPcache checks for file modification timestamps. | 0 (Disable for production; 1 for development) |
| `opcache.revalidate_freq` | How often OPcache checks for file changes (in seconds). | 60 (if `opcache.validate_timestamps` is enabled) |
These settings are also configured in `php.ini`. Restart your web server after making changes. See PHP OPcache for more in-depth information.
Monitoring Memory Usage
Regularly monitoring memory usage is critical for identifying potential problems. Use system monitoring tools (e.g., `top`, `htop`, `vmstat` on Linux) to track overall server memory usage. PHP also provides functions like `memory_get_usage()` for monitoring memory consumption within PHP scripts. Database server monitoring tools are also essential.
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