go /
net /
906cda9512f77671ab44f8c8563b13a8e707b230 http2: add configurable knobs for the server's receive window
Upload performance is poor when BDP is higher than the flow-control window.
Previously, the server's receive window was fixed at 64KB, which resulted in
very poor performance for high-BDP links. The receive window now defaults to
1MB and is configurable. The per-connection and per-stream windows are
configurable separately (both default to 1MB as suggested in golang/go#16512).
Previously, the server created a "fixedBuffer" for each request body. This is no
longer a good idea because a fixedBuffer has fixed size, which means individual
streams cannot use varying amounts of the available connection window. To
overcome this limitation, I replaced fixedBuffer with "dataBuffer", which grows
and shrinks based on current usage. The worst-case fragmentation of dataBuffer
is 32KB wasted memory per stream, but I expect that worst-case will be rare.
A slightly modified version of adg@'s grpcbench program shows a dramatic
improvement when increasing from a 64KB window to a 1MB window, especially at
higher latencies (i.e., higher BDPs). Network latency was simulated with netem,
e.g., `tc qdisc add dev lo root netem delay 16ms`.
Duration Latency Proto H2 Window
11ms±4.05ms 0s HTTP/1.1 -
17ms±1.95ms 0s HTTP/2.0 65535
8ms±1.75ms 0s HTTP/2.0 1048576
10ms±1.49ms 1ms HTTP/1.1 -
47ms±2.91ms 1ms HTTP/2.0 65535
10ms±1.77ms 1ms HTTP/2.0 1048576
15ms±1.69ms 2ms HTTP/1.1 -
88ms±11.29ms 2ms HTTP/2.0 65535
15ms±1.18ms 2ms HTTP/2.0 1048576
23ms±1.42ms 4ms HTTP/1.1 -
152ms±0.77ms 4ms HTTP/2.0 65535
23ms±0.94ms 4ms HTTP/2.0 1048576
40ms±1.54ms 8ms HTTP/1.1 -
288ms±1.67ms 8ms HTTP/2.0 65535
39ms±1.29ms 8ms HTTP/2.0 1048576
72ms±1.13ms 16ms HTTP/1.1 -
559ms±0.68ms 16ms HTTP/2.0 65535
71ms±1.12ms 16ms HTTP/2.0 1048576
136ms±1.15ms 32ms HTTP/1.1 -
1104ms±1.62ms 32ms HTTP/2.0 65535
135ms±0.96ms 32ms HTTP/2.0 1048576
264ms±0.95ms 64ms HTTP/1.1 -
2191ms±2.08ms 64ms HTTP/2.0 65535
263ms±1.57ms 64ms HTTP/2.0 1048576
Fixes golang/go#16512
Updates golang/go#17985
Updates golang/go#18404
Change-Id: Ied385aa94588337e98dad9475cf2ece2f39ba346
Reviewed-on: https://go-review.googlesource.com/37226
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
2 files changed
