Struct wasmtime::InstanceLimits

pub struct InstanceLimits {
    pub count: u32,
    pub memory_reservation_size: u64,
}

Represents the limits placed on instances by the pooling instance allocation strategy.

Fields

count: u32

The maximum number of concurrent instances supported (default is 1000).

memory_reservation_size: u64

The maximum size, in bytes, of host address space to reserve for each linear memory of an instance.

Note: this value has important performance ramifications.

On 64-bit platforms, the default for this value will be 6 GiB. A value of less than 4 GiB will force runtime bounds checking for memory accesses and thus will negatively impact performance. Any value above 4 GiB will start eliding bounds checks provided the offset of the memory access is less than (memory_reservation_size - 4 GiB). A value of 8 GiB will completely elide all bounds checks; consequently, 8 GiB will be the maximum supported value. The default of 6 GiB reserves less host address space for each instance, but a memory access with an offset above 2 GiB will incur runtime bounds checks.

On 32-bit platforms, the default for this value will be 10 MiB. A 32-bit host has very limited address space to reserve for a lot of concurrent instances. As a result, runtime bounds checking will be used for all memory accesses. For better runtime performance, a 64-bit host is recommended.

This value will be rounded up by the WebAssembly page size (64 KiB).

Trait Implementations

impl Clone for InstanceLimits

fn clone(&self) -> InstanceLimits

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Copy for InstanceLimits

impl Debug for InstanceLimits

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

Formats the value using the given formatter.

impl Default for InstanceLimits

fn default() -> Self

Returns the “default value” for a type.