book: indirection for faster message passing

1 files changed, 24 insertions, 0 deletions

diff --git a/book/en/src/by-example/tips.md b/book/en/src/by-example/tips.md
index 07a5c0b..79b9d71 100644
--- a/book/en/src/by-example/tips.md
+++ b/book/en/src/by-example/tips.md
@@ -89,3 +89,27 @@ after the function, not the interrupt / exception. Example below:
 ``` console
 $ cargo run --example binds
 {{#include ../../../../ci/expected/binds.run}}```
+
+## Indirection for faster message passing
+
+Message passing always involves copying the payload from the sender into a
+static variable and then from the static variable into the receiver. Thus
+sending a large buffer, like a `[u8; 128]`, as a message involves two expensive
+`memcpy`s. To minimize the message passing overhead one can use indirection:
+instead of sending the buffer by value, one can send an owning pointer into the
+buffer.
+
+One can use a global allocator to achieve indirection (`alloc::Box`,
+`alloc::Rc`, etc.), which requires using the nightly channel as of Rust v1.34.0,
+or one can use a statically allocated memory pool like [`heapless::Pool`].
+
+[`heapless::Pool`]: https://docs.rs/heapless/0.4.3/heapless/pool/index.html
+
+Here's an example where `heapless::Pool` is used to "box" buffers of 128 bytes.
+
+``` rust
+{{#include ../../../../examples/pool.rs}}
+```
+``` console
+$ cargo run --example binds
+{{#include ../../../../ci/expected/pool.run}}```