sync: document mpsc channel allocation behavior (#6773)

2026-08-29 00:00:11 +02:00 · 2024-08-16 12:31:03 +02:00
parent 56f3f40c15
commit 5ea3c63d7e
1 changed files with 16 additions and 0 deletions
@@ -78,6 +78,22 @@
 //! within a Tokio runtime, however it is still not tied to one specific Tokio
 //! runtime, and the sender may be moved from one Tokio runtime to another.
 //!
 //! # Allocation behavior
 //!
 //! <div class="warning">The implementation details described in this section may change in future
 //! Tokio releases.</div>
 //!
 //! The mpsc channel stores elements in blocks. Blocks are organized in a linked list. Sending
 //! pushes new elements onto the block at the front of the list, and receiving pops them off the
 //! one at the back. A block can hold 32 messages on a 64-bit target and 16 messages on a 32-bit
 //! target. This number is independent of channel and message size. Each block also stores 4
 //! pointer-sized values for bookkeeping (so on a 64-bit machine, each message has 1 byte of
 //! overhead).
 //!
 //! When all values in a block have been received, it becomes empty. It will then be freed, unless
 //! the channel's first block (where newly-sent elements are being stored) has no next block. In
 //! that case, the empty block is reused as the next block.
 //!
 //! [`Sender`]: crate::sync::mpsc::Sender
 //! [`Receiver`]: crate::sync::mpsc::Receiver
 //! [bounded-send]: crate::sync::mpsc::Sender::send()