diff options
Diffstat (limited to 'book/en/src/by-example/tips/indirection.md')
| -rw-r--r-- | book/en/src/by-example/tips/indirection.md | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/book/en/src/by-example/tips/indirection.md b/book/en/src/by-example/tips/indirection.md new file mode 100644 index 0000000..eef0d8e --- /dev/null +++ b/book/en/src/by-example/tips/indirection.md @@ -0,0 +1,26 @@ +# Using 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. + +Indirection can minimize message passing overhead: instead of sending the buffer by value, one can send an owning pointer into the buffer. + +One can use a global memory allocator to achieve indirection (`alloc::Box`, `alloc::Rc`, etc.), which requires using the nightly channel as of Rust v1.37.0, or one can use a statically allocated memory pool like [`heapless::Pool`]. + +[`heapless::Pool`]: https://docs.rs/heapless/0.5.0/heapless/pool/index.html + +As this example of approach goes completely outside of RTIC resource model with shared and local the program would rely on the correctness of the memory allocator, in this case `heapless::pool`. + +Here's an example where `heapless::Pool` is used to "box" buffers of 128 bytes. + +``` rust +{{#include ../../../../../rtic/examples/pool.rs}} +``` + +``` console +$ cargo run --target thumbv7m-none-eabi --example pool +``` + +``` console +{{#include ../../../../../rtic/ci/expected/pool.run}} +``` |
