Struct SystemMemoryStats 

pub struct SystemMemoryStats {
    pub rss_bytes: usize,
    pub allocated_bytes: usize,
    pub active_bytes: usize,
    pub mapped_bytes: usize,
    pub retained_bytes: usize,
    pub fragmentation_ratio: f64,
}

System memory statistics from jemalloc.

Fields

rss_bytes: usize

Resident Set Size — actual physical memory used.

allocated_bytes: usize

Total bytes allocated by the application.

active_bytes: usize

Total bytes in active pages (mapped and potentially dirty).

mapped_bytes: usize

Total bytes mapped by the allocator (may exceed active).

retained_bytes: usize

Total bytes retained in the allocator’s caches.

fragmentation_ratio: f64

Fragmentation ratio: (active - allocated) / active.

Measures how much memory the allocator has claimed from the OS (active pages) but isn’t actually used by application objects. This gap comes from jemalloc internal metadata, free-list fragmentation, and thread cache overhead.

Healthy: < 0.15 (15%). Warning: 0.15–0.25. Critical: > 0.25. A sustained ratio above 0.25 indicates severe fragmentation — the process is consuming significantly more RSS than its live data warrants, and OOM risk increases under memory pressure.

Implementations

impl SystemMemoryStats

pub fn query() -> Option<Self>

Query jemalloc for current system memory statistics.

Returns None if jemalloc introspection is unavailable.

pub fn is_fragmentation_critical(&self) -> bool

Returns true if fragmentation exceeds the warning threshold (25%).

Trait Implementations

impl Clone for SystemMemoryStats

fn clone(&self) -> SystemMemoryStats

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for SystemMemoryStats

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.