Tune HTTP/3 client performance - #892
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- Align QUIC flow-control windows with the HTTP/2 client (stream_receive_window / send_window = (1 << 30) - 1); quinn's default 1.25MB stream window caps per-stream throughput over real networks - Enlarge UDP socket buffers to 8MB (as far as the OS allows) to avoid packet loss at high request rates - Drop the endless_emitter channel from work_until: request workers now loop until the deadline semaphore closes, like the HTTP/2 path, removing a channel round-trip per request - Move the HTTP/3 connect path out of Client::client into connect_http3 Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Summary
Brings the HTTP/3 client's transport configuration in line with the HTTP/1/HTTP/2 implementations and removes per-request overhead from the
work_untilpath.stream_receive_window(1.25MB) caps per-stream throughput at 1.25MB/RTT over real networks. Setstream_receive_window/send_windowto(1 << 30) - 1, matching the window sizes the HTTP/2 client already uses (from nghttp2's default).net.core.rmem_maxis small.endless_emitterchannel fromwork_until: request workers previously consumed a token from a kanal channel per request, fed by a task sendingNonein a loop. Workers now loop until the deadline semaphore closes, matching the HTTP/2 implementation.Client::clientintoconnect_http3.Benchmarks
Loopback (WSL2, 32 cores, local quinn/h3 server): throughput unchanged within noise — ~100k req/s (
-c 50), ~200k req/s (-c 50 -p 10, on par with HTTP/1), 100% success at-c 100 -p 100. The window/buffer changes target real-network conditions (RTT > 0, tunedrmem_max), which loopback cannot exercise.Profiling (pprof) shows the remaining client CPU is dominated by h3's per-request QPACK encoding (~18%) and quinn's connection driver (~30%), so further gains would need upstream changes.
Test plan
cargo test/cargo test --features http3(79 tests pass)cargo clippy --features http3 --all-targetsclean--no-tuiagainst a local HTTP/3 server, including the restructuredwork_untildeadline handling🤖 Generated with Claude Code