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, where sysinfo returns Err(Unsupported)) the fields are present but zero. Likewise, any metric sysinfo fails to read is reported as zero rather than failing the whole stats response.