fix(s2n-quic-core): support higher bandwidth estimates #1650
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camshaft
reviewed
Mar 2, 2023
| @@ -2,4 +2,4 @@ | |||
| source: quic/s2n-quic-core/src/recovery/bbr/pacing.rs | |||
| expression: "" | |||
| --- | |||
| PacingRateUpdated { path_id: 0, bytes_per_second: 2747252, burst_size: 12000, pacing_gain: 2.77 } | |||
| PacingRateUpdated { path_id: 0, bytes_per_second: 2742301, burst_size: 12000, pacing_gain: 2.77 } | |||
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I see that all of these estimates are rounding down. This one is the most extreme with ~5000 bytes. I'm not sure it's a huge cause for concern but it could mean that we're not sending as fast since we're underestimating the bandwidth, right? Or were we overestimating before?
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Yeah we were overestimating before. The math previously would be
(1000/ 2.77)/.99 = 364.657 nanos/byte, which truncates to 364 nanos/byte = 2747252 bytes/sec
Now the math is:
1000 * 1024 / 2.77 / .99 = 373409.182 nanos/kibibyte, which truncates to 373409 nanos/kibibyte = 2742301 bytes/sec
camshaft
approved these changes
Mar 2, 2023
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Resolved issues:
resolves #1440
Description of changes:
The current representation of a bandwidth estimate used mostly by BBR (but also for CUBIC pacing) can support a maximum bandwidth of 1GB/sec. This may not be sufficient for data center usage, so this change allows for support up to ~1TB/sec.
Call-outs:
Many snapshot tests changed slightly, this is due to the new code storing bandwidth more precisely.
Testing:
Updated and added some tests
By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.