Function system_stats_subtree 

pub fn system_stats_subtree() -> Value

Build the system subtree: process- and host-level metrics that don’t belong to any single subsystem. Numbers only; never asserts a specific value, since these vary per host.

Disk fields sum across all disks the OS exposes. Load average is reported as three floats; on platforms that don’t compute load averages (notably Windows) the fields are present but zero.