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refactor(http2): change rtt weighted moving average beta to 1/8

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This commit is contained in:
Sean McArthur
2020-04-16 17:00:06 -07:00
parent 5f6ce3c733
commit aafeeb7638
1 changed files with 7 additions and 10 deletions
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17
src/proto/h2/ping.rs
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@@ -50,7 +50,6 @@ pub(super) fn channel(ping_pong: PingPong, config: Config) -> (Recorder, Ponger)
let bdp = config.bdp_initial_window.map(|wnd| Bdp {
bdp: wnd,
max_bandwidth: 0.0,
samples: 0,
rtt: 0.0,
});
@@ -142,8 +141,6 @@ struct Bdp {
bdp: u32,
/// Largest bandwidth we've seen so far.
max_bandwidth: f64,
/// Count of samples made (ping sent and received)
samples: usize,
/// Round trip time in seconds
rtt: f64,
}
@@ -301,10 +298,9 @@ impl Ponger {
}
}
if let Some(ref mut bdp) = self.bdp {
if self.bdp.is_some() {
let bytes = locked.bytes.expect("bdp enabled implies bytes");
locked.bytes = Some(0); // reset
bdp.samples += 1;
trace!("received BDP ack; bytes = {}, rtt = {:?}", bytes, rtt);
(bytes, rtt)
} else {
@@ -394,11 +390,12 @@ impl Bdp {
// average the rtt
let rtt = seconds(rtt);
if self.samples < 10 {
// Average the first 10 samples
self.rtt += (rtt - self.rtt) / (self.samples as f64);
if self.rtt == 0.0 {
// First sample means rtt is first rtt.
self.rtt = rtt;
} else {
self.rtt += (rtt - self.rtt) / 0.9;
// Weigh this rtt as 1/8 for a moving average.
self.rtt += (rtt - self.rtt) * 0.125;
}
// calculate the current bandwidth
@@ -414,7 +411,7 @@ impl Bdp {
// if the current `bytes` sample is at least 2/3 the previous
// bdp, increase to double the current sample.
if (bytes as f64) >= (self.bdp as f64) * 0.66 {
if bytes >= self.bdp as usize * 2 / 3 {
self.bdp = (bytes * 2).min(BDP_LIMIT) as WindowSize;
trace!("BDP increased to {}", self.bdp);
Some(self.bdp)