opcachememoryconsumption

Opcache memory consumption refers to the amount of server memory used by the PHP OPcache extension to store precompiled PHP bytecode and related data. OPcache speeds PHP execution by keeping compiled scripts in memory, so memory consumption is a function of how many scripts are cached, their compiled size, and the space taken by interned strings.

The primary controls are configuration directives and runtime status. The directive opcache.memory_consumption sets the maximum memory (in megabytes) allocated to the opcode cache. The opcache.max_accelerated_files directive limits how many files can be cached. The opcache.interned_strings_buffer directive reserves memory for interned strings, which are shared across cached scripts to reduce duplication. Together, these settings determine the upper bound of memory that OPcache may use.

Memory usage grows with the number of cached scripts and the size of each script’s compiled opcodes, plus overhead for cache metadata and interned strings. If the cache fills up, OPcache may evict the least recently used entries, which can affect performance if frequently accessed files are removed.

Monitoring and tuning typically rely on runtime status. The PHP function opcache_get_status and phpinfo() provide metrics such as memory_consumed (or equivalent) and the number of cached scripts. Adjustments to opcache.memory_consumption, opcache.max_accelerated_files, or opcache.interned_strings_buffer should be made based on observed cache hit rates and memory availability.

Common considerations include balancing memory allocation against available RAM, reducing the number of cached files through code organization, and ensuring appropriate revalidation settings (opcache.validate_timestamps and opcache.revalidate_freq) to minimize unnecessary cache churn while keeping code up to date.