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# Objective - Contributes to #16877 ## Solution - Expanded `bevy_platform_support::sync` module to provide API-compatible replacements for `std` items such as `RwLock`, `Mutex`, and `OnceLock`. - Removed `spin` from all crates except `bevy_platform_support`. ## Testing - CI --- ## Notes - The sync primitives, while verbose, entirely rely on `spin` for their implementation requiring no `unsafe` and not changing the status-quo on _how_ locks actually work within Bevy. This is just a refactoring to consolidate the "hacks" and workarounds required to get a consistent experience when either using `std::sync` or `spin`. - I have opted to rely on `std::sync` for `std` compatible locks, maintaining the status quo. However, now that we have these locks factored out into the own module, it would be trivial to investigate alternate locking backends, such as `parking_lot`. - API for these locking types is entirely based on `std`. I have implemented methods and types which aren't currently in use within Bevy (e.g., `LazyLock` and `Once`) for the sake of completeness. As the standard library is highly stable, I don't expect the Bevy and `std` implementations to drift apart much if at all. --------- Co-authored-by: BD103 <59022059+BD103@users.noreply.github.com> Co-authored-by: Benjamin Brienen <benjamin.brienen@outlook.com> |
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Bevy Tasks
A refreshingly simple task executor for bevy. :)
This is a simple threadpool with minimal dependencies. The main usecase is a scoped fork-join, i.e. spawning tasks from
a single thread and having that thread await the completion of those tasks. This is intended specifically for
bevy as a lighter alternative to rayon for this specific usecase. There are also utilities for
generating the tasks from a slice of data. This library is intended for games and makes no attempt to ensure fairness
or ordering of spawned tasks.
It is based on async-executor, a lightweight executor that allows the end user to manage their own threads.
async-executor is based on async-task, a core piece of async-std.
Usage
In order to be able to optimize task execution in multi-threaded environments, bevy provides three different thread pools via which tasks of different kinds can be spawned. (The same API is used in single-threaded environments, even if execution is limited to a single thread. This currently applies to Wasm targets.) The determining factor for what kind of work should go in each pool is latency requirements:
-
For CPU-intensive work (tasks that generally spin until completion) we have a standard [
ComputeTaskPool] and an [AsyncComputeTaskPool]. Work that does not need to be completed to present the next frame should go to the [AsyncComputeTaskPool]. -
For IO-intensive work (tasks that spend very little time in a "woken" state) we have an [
IoTaskPool] whose tasks are expected to complete very quickly. Generally speaking, they should just await receiving data from somewhere (i.e. disk) and signal other systems when the data is ready for consumption. (likely via channels)
no_std Support
To enable no_std support in this crate, you will need to disable default features, and enable the edge_executor and critical-section features. For platforms without full support for Rust atomics, you may also need to enable the portable-atomic feature.