docs(design): evaluate async I/O for SSH transport path (#1593)#3900
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Document the current synchronous SSH transport, the network-vs-disk overlap bottleneck, and two async candidates (tokio::process and embedded russh). Recommend staging behind a --features async-ssh flag, default off until benchmarks show > 10% gain.
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Document the current synchronous SSH transport, the network-vs-disk overlap bottleneck, and two async candidates (tokio::process and embedded russh). Recommend staging behind a --features async-ssh flag, default off until benchmarks show > 10% gain.
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Summary
sshsubprocess,std::process::ChildStdout/ChildStdin) and identify the network-vs-disk overlap bottleneck.tokio::process::Child(lightweight swap, reuses the existing tokio runtime) and embedded russh fromcrates/rsync_io/src/ssh/embedded/(eliminates the subprocess entirely; tracked under Refactor drive workflow into dedicated modules #1782).--features async-sshcargo flag, default off until benchmarks show a sustained > 10% wall-clock improvement.Closes part of #1593 (design phase).
Test plan
docs/design/async-ssh-transport.mdrenders correctly on GitHub.