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Start documenting Metering

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This commit is contained in:
Brandon Fish 2019-06-02 15:42:25 -05:00
parent f9c8f41232
commit 8fdc4f9bc2
1 changed files with 12 additions and 0 deletions
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lib/middleware-common/src/metering.rs
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@ -8,6 +8,18 @@ use wasmer_runtime_core::{
static INTERNAL_FIELD: InternalField = InternalField::allocate(); static INTERNAL_FIELD: InternalField = InternalField::allocate();
/// Metering is a compiler middleware that calculates the cost of WebAssembly instructions at compile
/// time and will count the cost of executed instructions at runtime. Within the Metering functionality,
/// this instruction cost is called `points`.
///
/// The Metering struct takes a `limit` parameter which is the maximum number of points which can be
/// used by an instance during a function call. If this limit is exceeded, the function call will
/// trap. Each instance has a `points_used` field which can be used to track points used during
/// a function call and should be set back to zero after a function call.
///
/// Each compiler backend with Metering enabled should produce the same cost used at runtime for
/// the same function calls so we can say that the metering is deterministic.
///
pub struct Metering { pub struct Metering {
limit: u64, limit: u64,
current_block: u64, current_block: u64,