Struct SystemLocalityInformationTable 

#[repr(C, packed(1))]
pub struct SystemLocalityInformationTable {
    pub header: SDTHeader,
    pub system_localities_num: u64,
}

System Locality Information Table (SLIT)

This optional table provides a matrix that describes the relative distance (memory latency) between all System Localities, which are also referred to as Proximity Domains. Systems employing a Non Uniform Memory Access (NUMA) architecture contain collections of hardware resources including for example, processors, memory, and I/O buses, that comprise what is known as a “NUMA node”. Processor accesses to memory or I/O resources within the local NUMA node is generally faster than processor accesses to memory or I/O resources outside of the local NUMA node.

The value of each Entry[i,j] in the SLIT table, where i represents a row of a matrix and j represents a column of a matrix, indicates the relative distances from System Locality / Proximity Domain i to every other System Locality j in the system (including itself).

The i,j row and column values correlate to Proximity Domain values in the System Resource Affinity Table (SRAT), and to values returned by _PXM objects in the ACPI namespace.

The entry value is a one-byte unsigned integer. The relative distance from System Locality i to System Locality j is the i*N + j entry in the matrix, where N is the number of System Localities. Except for the relative distance from a System Locality to itself, each relative distance is stored twice in the matrix. This provides the capability to describe the scenario where the relative distances for the two directions between System Localities is different.

The diagonal elements of the matrix, the relative distances from a System Locality to itself are normalized to a value of 10. The relative distances for the non-diagonal elements are scaled to be relative to 10. For example, if the relative distance from System Locality i to System Locality j is 2.4, a value of 24 is stored in table entry iN+ j and in jN+ i, where N is the number of System Localities.

If one locality is unreachable from another, a value of 255 (0xFF) is stored in that table entry. Distance values of 0-9 are reserved and have no meaning.

JJ’s Note: Even though the entry field in specs say it’s a 2-D array, having any kernel use it as a 2-D array destroys performance.
The best way to use the entry field is to use it as a flat slice. This is the reason why you don’t see the entry field in the struct itself.

Fields

header: SDTHeader

• Signature - “SLIT”

system_localities_num: u64

Indicates the number of System Localities in the system.

Implementations

impl SystemLocalityInformationTable

pub const fn entries_flat(&self) -> &[u8]

Trait Implementations

impl Clone for SystemLocalityInformationTable

fn clone(&self) -> SystemLocalityInformationTable

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for SystemLocalityInformationTable