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perf(transport): raise the per-path transmit queue quota to 1 MiB - #41
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At ~1 Gbps one drive can hand a path over 256 KiB of packets, so the per-(conn, path) quota refused them, xquic got EAGAIN, and it retried on every wakeup until the queue drained: 100k-150k refusals per 40 s on the WAN MITM bench, each logged as three ERROR lines by xquic. Raise the quota to 1 MiB (resume below 512 KiB, total 4 MiB) and grow queues on use instead of reserving the quota up front, so an idle (conn, path) costs nothing. On the bench refusals dropped to ~0 and throughput rose from 814 to 1017 Mbps single path and 703 to 919 Mbps multipath (median of 3). The fabric quota tests now run cubic: under the simulated network BBR's window settles below one 1 MiB quota, so the queue could never fill.
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At ~1 Gbps one drive can hand a path over 256 KiB of packets, so the per-(conn, path) quota refused them, xquic got EAGAIN, and it retried on every wakeup until the queue drained: 100k-150k refusals per 40 s on the WAN MITM bench, each logged as three ERROR lines by xquic. Raise the quota to 1 MiB (resume below 512 KiB, total 4 MiB) and grow queues on use instead of reserving the quota up front, so an idle (conn, path) costs nothing.
On the bench refusals dropped to ~0 and throughput rose from 814 to 1017 Mbps single path and 703 to 919 Mbps multipath (median of 3).
The fabric quota tests now run cubic: under the simulated network BBR's window settles below one 1 MiB quota, so the queue could never fill.