Enum PrefetchMode 

pub enum PrefetchMode {
    Off,
    Sequential,
    WillNeed,
    Auto,
}

Selects the read-ahead hint applied to the active disk-access backend.

See StorageConfig::prefetch. Sequential / WillNeed map to the corresponding madvise(2) advice on the mmap backend; on the direct-I/O backend any non-Off value enables the StorageConfig::direct_io_prefetch_bytes read-ahead window.

Variants

Off

No explicit prefetch hint; rely on default kernel behaviour.

Sequential

Hint sequential access (aggressive read-ahead, drop-behind).

WillNeed

Hint that the mapped/region bytes will be needed soon (eager fault-in).

Auto

Let the backend choose. For mmap this issues no madvise and relies on the kernel’s default read-ahead: MADV_SEQUENTIAL’s drop-behind evicts hot pages under concurrent write load and inflates the read-side p99 tail (issue #1143), so Auto avoids it while keeping the isolated mmap win. For direct I/O it enables the windowed read-ahead (StorageConfig::direct_io_prefetch_bytes). Request PrefetchMode::Sequential explicitly for MADV_SEQUENTIAL behaviour.

Trait Implementations

impl Clone for PrefetchMode

fn clone(&self) -> PrefetchMode

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for PrefetchMode

impl Debug for PrefetchMode

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

Formats the value using the given formatter.

impl Default for PrefetchMode

fn default() -> PrefetchMode

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for PrefetchMode

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Eq for PrefetchMode

impl PartialEq for PrefetchMode

fn eq(&self, other: &PrefetchMode) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl Serialize for PrefetchMode

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for PrefetchMode