81 lines
1.6 KiB
Go
81 lines
1.6 KiB
Go
|
package main
|
||
|
|
|
||
|
|
import (
|
||
|
|
"math/bits"
|
||
|
|
"sync"
|
||
|
|
"sync/atomic"
|
||
|
|
)
|
||
|
|
|
||
|
|
const (
|
||
|
|
lossSlots = 1 << 16
|
||
|
|
lossWords = lossSlots / 64
|
||
|
|
)
|
||
|
|
|
||
|
|
type lossWindow struct {
|
||
|
|
mu sync.Mutex
|
||
|
|
base uint64
|
||
|
|
inited bool
|
||
|
|
bits []uint64
|
||
|
|
lost atomic.Uint64
|
||
|
|
late atomic.Uint64
|
||
|
|
}
|
||
|
|
|
||
|
|
func newLossWindows(n int) []lossWindow {
|
||
|
|
w := make([]lossWindow, n)
|
||
|
|
for i := range w {
|
||
|
|
w[i].bits = make([]uint64, lossWords)
|
||
|
|
}
|
||
|
|
return w
|
||
|
|
}
|
||
|
|
|
||
|
|
// A sequence number is only judged once it falls out of the window, so frames
|
||
|
|
// still queued in another rx worker are never miscounted as lost.
|
||
|
|
func (w *lossWindow) observe(seq uint64) {
|
||
|
|
w.mu.Lock()
|
||
|
|
if !w.inited {
|
||
|
|
// Start half a window below the first sequence seen, so frames another
|
||
|
|
// rx worker is still holding land inside the window rather than late.
|
||
|
|
if seq > lossSlots/2 {
|
||
|
|
w.base = seq - lossSlots/2
|
||
|
|
}
|
||
|
|
w.inited = true
|
||
|
|
}
|
||
|
|
if seq < w.base {
|
||
|
|
w.mu.Unlock()
|
||
|
|
w.late.Add(1)
|
||
|
|
return
|
||
|
|
}
|
||
|
|
if seq >= w.base+lossSlots {
|
||
|
|
w.evict(seq - lossSlots + 1)
|
||
|
|
}
|
||
|
|
idx := seq & (lossSlots - 1)
|
||
|
|
w.bits[idx>>6] |= 1 << (idx & 63)
|
||
|
|
w.mu.Unlock()
|
||
|
|
}
|
||
|
|
|
||
|
|
func (w *lossWindow) evict(newBase uint64) {
|
||
|
|
span := newBase - w.base
|
||
|
|
if span >= lossSlots {
|
||
|
|
var missing uint64
|
||
|
|
for i := range w.bits {
|
||
|
|
missing += uint64(64 - bits.OnesCount64(w.bits[i]))
|
||
|
|
w.bits[i] = 0
|
||
|
|
}
|
||
|
|
w.lost.Add(missing + span - lossSlots)
|
||
|
|
w.base = newBase
|
||
|
|
return
|
||
|
|
}
|
||
|
|
var missing uint64
|
||
|
|
for s := w.base; s < newBase; s++ {
|
||
|
|
idx := s & (lossSlots - 1)
|
||
|
|
word, bit := idx>>6, uint64(1)<<(idx&63)
|
||
|
|
if w.bits[word]&bit == 0 {
|
||
|
|
missing++
|
||
|
|
continue
|
||
|
|
}
|
||
|
|
w.bits[word] &^= bit
|
||
|
|
}
|
||
|
|
w.lost.Add(missing)
|
||
|
|
w.base = newBase
|
||
|
|
}
|