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book: indirection for faster message passing
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5 changed files with 128 additions and 3 deletions
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@ -89,3 +89,27 @@ after the function, not the interrupt / exception. Example below:
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``` console
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$ cargo run --example binds
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{{#include ../../../../ci/expected/binds.run}}```
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## Indirection for faster message passing
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Message passing always involves copying the payload from the sender into a
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static variable and then from the static variable into the receiver. Thus
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sending a large buffer, like a `[u8; 128]`, as a message involves two expensive
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`memcpy`s. To minimize the message passing overhead one can use indirection:
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instead of sending the buffer by value, one can send an owning pointer into the
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buffer.
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One can use a global allocator to achieve indirection (`alloc::Box`,
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`alloc::Rc`, etc.), which requires using the nightly channel as of Rust v1.34.0,
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or one can use a statically allocated memory pool like [`heapless::Pool`].
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[`heapless::Pool`]: https://docs.rs/heapless/0.4.3/heapless/pool/index.html
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Here's an example where `heapless::Pool` is used to "box" buffers of 128 bytes.
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``` rust
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{{#include ../../../../examples/pool.rs}}
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```
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``` console
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$ cargo run --example binds
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{{#include ../../../../ci/expected/pool.run}}```
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