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The egress gateway limits kernel send queues to slow destinations - #3322
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Chuang Wang (chuangw6)
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An upload to a destination that reads slowly can put the tunnel's 1 MiB HTTP/2 stream window into the send queue of the gateway's socket to the destination, charged to the gateway's container. Set TCP_NOTSENT_LOWAT to 16 KiB on the egress listener and on the four dynamic forward proxy clusters, so the backlog stays behind Envoy's buffer limit and the tunnel's flow control. In the Envoy benchmark a stalled tunnel alone on its connection dropped from 1420 to 48 KiB of socket memory, with throughput within run-to-run noise. Fixed buffer sizes are left out: a fixed SO_RCVBUF cut a tunnel's throughput by 90% at 10 ms round trip. Signed-off-by: Chuang Wang <chuangw@google.com>
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Bowei Du (bowei)
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Merged into #3320. |
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Part of #3133; design and data in
docs/network-socket-memory.md(#3319).The egress gateway sets
TCP_NOTSENT_LOWATto 16 KiB on itsegresslistener (sockets from atunnel) and on its four forward proxy clusters (sockets to destinations). Without it, an upload to a slow destination can put the tunnel's 1 MiB HTTP/2 window into the socket's send queue. A test checks the listener and every forward proxy cluster keep it. To turn it off, delete those blocks.Download speed at +10 ms is unchanged (309 vs 308 MB/s). Fixed 64 KiB buffers cut it to 10 MB/s, so they are left out.