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feat(host/windows): USO batched send for the GameStream video plane

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The GameStream video sender did one send() syscall per packet on Windows
(the #[cfg(not(target_os="linux"))] sendmmsg_all fallback), capping
throughput at high packet rates. Wire it to UDP Send Offload (the Windows
analogue of Linux GSO) so each paced 16-packet burst goes out in one
WSASendMsg(UDP_SEND_MSG_SIZE) syscall instead of 16, preserving the
microburst pacing.

Expose a reusable punktfunk_core::transport::send_uso_all (Windows-only)
that reuses the proven native-plane USO primitive (send_one_uso + the uso
on/off latch + uso_unsupported), with the same uniform-size guard and
≤512-segment chunking as UdpTransport::send_gso. It returns how many leading
packets it sent via USO; the GameStream sendmmsg_all sends any remainder
(USO off via PUNKTFUNK_GSO=0, a size-mixed burst, or a frame's short final
packet) with per-packet send. On-wire packet boundaries are unchanged.

Resolves #4 in docs/apollo-comparison.md. Linux build unaffected;
punktfunk-core type-checks for x86_64-pc-windows-msvc. Host Windows compile
deferred to CI / dev box.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
Enrico Bühler
2026-06-16 10:21:33 +00:00
parent ba4e9a8672
commit 0324719b6e
3 changed files with 69 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files
crates/punktfunk-host/src/gamestream/stream.rs
+18 -3
View File
@@ -180,9 +180,24 @@ fn sendmmsg_all(sock: &UdpSocket, pkts: &[Vec<u8>]) -> std::io::Result<()> {
Ok(())
}
/// Portable fallback (non-Linux dev builds — GameStream hosting never ships there): one
/// syscall per packet.
#[cfg(not(target_os = "linux"))]
/// Windows: coalesce each paced burst's equal-size packets into `WSASendMsg(UDP_SEND_MSG_SIZE)`
/// super-buffers (UDP Send Offload — the Windows analogue of Linux GSO), so a 16-packet burst is one
/// syscall instead of 16. Reuses the proven core USO primitive; it returns how many leading packets
/// it sent, and we send any remainder (USO off via `PUNKTFUNK_GSO=0`, a size-mixed burst, or a
/// frame's short final packet) with a per-packet `send`. The socket is connected.
#[cfg(target_os = "windows")]
fn sendmmsg_all(sock: &UdpSocket, pkts: &[Vec<u8>]) -> std::io::Result<()> {
let refs: Vec<&[u8]> = pkts.iter().map(|p| p.as_slice()).collect();
let n = punktfunk_core::transport::send_uso_all(sock, &refs)?;
for p in &pkts[n..] {
sock.send(p)?;
}
Ok(())
}
/// Portable fallback (other non-Linux dev builds, e.g. macOS — GameStream hosting never ships there):
/// one syscall per packet.
#[cfg(not(any(target_os = "linux", target_os = "windows")))]
fn sendmmsg_all(sock: &UdpSocket, pkts: &[Vec<u8>]) -> std::io::Result<()> {
for p in pkts {
sock.send(p)?;