feat(runtime): Track block gas allowance in builtins #4345
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| @@ -93,6 +95,9 @@ pub enum BuiltinActorError { | |||
| /// Actor's inner error encoded as a String. | |||
| #[display(fmt = "Builtin execution resulted in error: {_0}")] | |||
| Custom(LimitedStr<'static>), | |||
| /// Occurs if a builtin actor execution does not fit in the current block. | |||
| #[display(fmt = "Block gas allowance exceeded")] | |||
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Im wondering If we could abstract it since it more about how system implemented rather than each particular builtin
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| gas_spent += to_spend; | ||
| gas_left -= to_spend; |
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Safe due to a check above - if gas_left is less than to_spend we abort earlier
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But for the sake of universality we can use saturated arithmetics - no problem
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| gas_spent += to_spend; | ||
| gas_left -= to_spend; |
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pallets/gear/src/builtin.rs
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| pub type HandleFn<C, E> = dyn Fn(&StoredDispatch, &mut C) -> Result<Payload, E>; | ||
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| /// Builtin actor `max_gas` function signature. | ||
| // TODO: let the weight function take a complexity argument similar to extrinsics weight functions |
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Sounds like a new epic story so definitely needs an issue =)
pallets/gear-builtin/src/lib.rs
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| } | ||
| } | ||
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| /// TODO: |
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It would be nice to have some description
| context: &mut BuiltinContext, | ||
| ) -> Result<Payload, BuiltinActorError>; | ||
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| /// Returns the maximum gas that can be spent by the actor. |
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Does zero value get interpreted in special way?
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Does zero value get interpreted in special way?
Not really: it'll just always pass the "initial screening" in the BuiltinDispatcher, but checks inside the handle() still remain (every time the gas counter is charged). However, if the max_gas() reports an accurate estimation, the handle would be skipped entirely and message re-queued. In the latter case we are certain no gas is going to be wasted as opposed to the situation if we still have to requeue the message after all, but only know it half way down inside the handle.
Addresses #3752.
The initial implementation of builtin actors overlooked the need of keeping track of the block gas allowance. So far only individual message gas limit has been taken in consideration.
To address this, the way how gas usage is tracked in builtin actors has been modified. Specifically:
BuiltinActor::handlemethod signature has been change to return just aResult<Payload, BuilintActorErrorand not a tuple with actual gas burned; instead, gas usage is captured by theGasCounter(as a part of mutablecontextpassed as an input tohandle);BuiltinActor::max_gas()method has been added to the trait to allow builtin actors report the maximum possible amount of gas that can be burned during a message processing. Thehandlewould only be called if it fits in the current block in the worst possible case based on themax_gasoutput (similarly to how it is decided whether an extrinsic is added to a block based on its weight). It doesn't have to be 100% accurate, I guess - but better be not too far from real values.The refactoring has rendered the codebase more readable.
TODO (#4396):
max_gas()for every builtin actor with actual values - either through benchmarking or theoretically.