Requirements
Requirements
This page lists what the code checks for or reads. Anything not here is not required.
Linux
fpm-tune reads the memory budget from the cgroup php-fpm runs in (v2 or v1) or from /proc/meminfo, finds masters in the process table, and reads each worker's memory under /proc/<pid>. All of that is Linux. The macOS build compiles and is for development; it cannot size a host.
php-fpm with a status page
A pool is sized from its status page, pm.status_path, scraped over the pool's own listen socket. A pool without one is not sized: plan leaves it out, and serve warns about it by name. sudo fpm-tune enable-status turns the page on for every pool that lacks one (as do apply and serve --apply), by writing zz-fpm-tune-status.conf and reloading.
fpm-tune also runs php-fpm -tt to read the effective configuration and php-fpm -t to validate a change, and reloads with SIGUSR2. The drop-ins go into the pool directory the master includes; a master that includes no directory cannot be written.
Root, for the commands that write
apply, serve --apply, enable-status, install-service, mode and apply-now need root: they write to the pool directory or /etc/fpm-tune, talk to systemd, or use the control socket, which is root's. plan, serve (advisory) and top run as the php-fpm user or as root; they read the pool configuration, the status pages and the workers' /proc entries. Run as any other user, plan still prints the plan and says it cannot write /var/lib/fpm-tune, so no baseline is recorded.
Kernel features, and what happens without them
| feature | since | used for | without it |
|---|---|---|---|
/proc/<pid>/smaps_rollup |
4.14 | a worker's proportional set size, so shared pages are not counted once per worker | the worker's RSS |
MemAvailable in /proc/meminfo |
3.14 | the used by other services line on a host without a cgroup limit |
no neighbour subtraction; only the reserve is held back |
cgroup v2 memory.peak |
5.19 | the cgroup's high-water mark, in the recommendation file and on /metrics |
a running maximum of memory.current, kept by the daemon |
A cgroup v1 host reads memory.limit_in_bytes, memory.usage_in_bytes and memory.max_usage_in_bytes instead.
systemd, for the service
install-service and mode write a unit under /etc/systemd/system and call systemctl. Without systemd, run fpm-tune serve under whatever supervises processes on the host; nothing else depends on systemd.
A state directory
/var/lib/fpm-tune holds the learned baselines, the backup and transaction record of a change in flight, the recommendation file, the control socket and the state lock. It is created on first run by a user who may; under systemd, StateDirectory=fpm-tune in the unit creates it. The per-pool-directory locks go under /run/fpm-tune.