This PR provides the infrastructure for the pov-reclaim mechanism discussed in #209. The goal is to provide the current proof size to the runtime so it can be used to reclaim storage weight. ## New Host Function - A new host function is provided [here](https://github.com/skunert/polkadot-sdk/blob/5b317fda3be205f4136f10d4490387ccd4f9765d/cumulus/primitives/pov-reclaim/src/lib.rs#L23). It returns the size of the current proof size to the runtime. If recording is not enabled, it returns 0. ## Implementation Overview - Implement option to enable proof recording during import in the client. This is currently enabled for `polkadot-parachain`, `parachain-template` and the cumulus test node. - Make the proof recorder ready for no-std. It was previously only enabled for std environments, but we need to record the proof size in `validate_block` too. - Provide a recorder implementation that only the records the size of incoming nodes and does not store the nodes itself. - Fix benchmarks that were broken by async backing changes - Provide new externalities extension that is registered by default if proof recording is enabled. - I think we should discuss the naming, pov-reclaim was more intuitive to me, but we could also go with clawback like in the issue. ## Impact of proof recording during import With proof recording: 6.3058 Kelem/s Without proof recording: 6.3427 Kelem/s The measured impact on the importing performance is quite low on my machine using the block import benchmark. With proof recording I am seeing a performance hit of 0.585%. --------- Co-authored-by: command-bot <> Co-authored-by: Davide Galassi <davxy@datawok.net> Co-authored-by: Bastian Köcher <git@kchr.de>
Substrate runtime api
The Substrate runtime api is the crucial interface between the node and the runtime.
Every call that goes into the runtime is done with a runtime api. The runtime apis are not fixed.
Every Substrate user can define its own apis with
decl_runtime_apis and implement them in
the runtime with impl_runtime_apis.
Every Substrate runtime needs to implement the [Core] runtime api. This api provides the basic
functionality that every runtime needs to export.
Besides the macros and the [Core] runtime api, this crates provides the [Metadata] runtime
api, the [ApiExt] trait, the [CallApiAt] trait and the [ConstructRuntimeApi] trait.
On a meta level this implies, the client calls the generated API from the client perspective.
License: Apache-2.0