PHP-FPM & performance
How BOA sizes and tunes the PHP execution tier: the RAM budget, master and tenant pool workers and memory_limit, the opcache/APCu shares, and the cache stack.
How BOA sizes and tunes the PHP execution tier in production: the box-wide RAM
budget, per-pool worker and memory_limit policy (master wwwNN vs plan-based
tenant pools), the opcache/APCu shares, the Valkey/Redis cache stack, and the
cron/cache failure modes that show up as intermittent plugin errors.
Two pool families exist on every host — CPU-sized master pools and plan-sized
tenant pools — and all pools run ondemand, so an idle version pool consumes
near-zero regardless of its pm.max_children ceiling. Capacity is governed by
_php_budget_for_ram (RAM ladder), _satellite_tune_fpm_config (tenant pools)
and _tune_web_server_config (master pools), with a set of _PHP_FPM_* override
knobs that pin any computed value.
The pages below cover FPM capacity sizing and the override knobs, the opcache and APCu shares with the read-only samplers, and diagnosing the cache and cron failure modes that surface as intermittent plugin errors on busy hosts.
Related
- Host control files & INI reference —
_RESERVED_RAM,_PHP_FPM_DENY, INI precedence. - Database (MySQL/Percona) — the database tier on the same hosts.
- Self-healing monitor stack —
minute.shcadence that launchesfpm_tune.shand the FPM reload sentinel handler. - Reference appendix — consolidated
_PHP_FPM_*/_USE_*variable table.
FPM capacity sizing
How BOA sizes PHP-FPM: the box-wide RAM budget from installed memory, master versus tenant pool pm.max_children, the shared and dedicated plan model, and the override knobs.
opcache & APCu
How BOA sizes the opcache and APCu shares from the RAM budget, what it writes into each phpNN.ini, the Valkey/Redis cache settings, and the read-only fpm_tune/fpmreport samplers.
Cache & cron tuning
Diagnosing intermittent plugin-not-found errors on busy hosts: Valkey memory starvation, drush cache poisoning, HDD autoloader timeouts, cron tuning, and the graceful APCu flush.