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Commit fa29e50f authored by Juliusz Chroboczek's avatar Juliusz Chroboczek
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Split writer loop into multiple threads. 

This improves both scaling and fairness in the case where a single
track is being sent to large numbers of receivers.  We avoid
communication overhead by growing the number of threads as the
square root of the number of receivers.
parent 8d58571d
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Inline Side-by-side
Showing with 335 additions and 142 deletions
rtpconn.go
View file @ fa29e50f
......@@ -189,7 +189,7 @@ type rtpUpTrack struct {
firSeqno uint32
localCh chan localTrackAction
writerDone chan struct{}
readerDone chan struct{}
mu sync.Mutex
cname string
......@@ -207,7 +207,7 @@ type localTrackAction struct {
func (up *rtpUpTrack) notifyLocal(add bool, track downTrack) {
select {
case up.localCh <- localTrackAction{add, track}:
case <-up.writerDone:
case <-up.readerDone:
}
}
......@@ -426,7 +426,7 @@ func newUpConn(c client, id string) (*rtpUpConnection, error) {
rate: estimator.New(time.Second),
jitter: jitter.New(remote.Codec().ClockRate),
localCh: make(chan localTrackAction, 2),
writerDone: make(chan struct{}),
readerDone: make(chan struct{}),
}
conn.tracks = append(conn.tracks, track)
......@@ -451,21 +451,16 @@ func newUpConn(c client, id string) (*rtpUpConnection, error) {
return conn, nil
}
type packetIndex struct {
seqno uint16
index uint16
delay uint32
}
func readLoop(conn *rtpUpConnection, track *rtpUpTrack) {
isvideo := track.track.Kind() == webrtc.RTPCodecTypeVideo
ch := make(chan packetIndex, 32)
defer close(ch)
go writeLoop(conn, track, ch)
writers := rtpWriterPool{conn: conn, track: track}
defer func() {
writers.close()
close(track.readerDone)
}()
isvideo := track.track.Kind() == webrtc.RTPCodecTypeVideo
buf := make([]byte, packetcache.BufSize)
var packet rtp.Packet
drop := 0
for {
bytes, err := track.track.Read(buf)
if err != nil {
......@@ -496,145 +491,22 @@ func readLoop(conn *rtpUpConnection, track *rtpUpTrack) {
}
}
if drop > 0 {
if packet.Marker {
// last packet in frame
drop = 0
} else {
drop--
}
continue
}
_, rate := track.rate.Estimate()
delay := uint32(rtptime.JiffiesPerSec / 1024)
if rate > 512 {
delay = rtptime.JiffiesPerSec / rate / 2
}
pi := packetIndex{packet.SequenceNumber, index, delay}
select {
case ch <- pi:
default:
// the writer is congested
if isvideo {
// keep dropping until the end of the frame
if isvideo && !packet.Marker {
drop = 7
}
} else {
// try again with half the delay on our side
timer := time.NewTimer(rtptime.ToDuration(
uint64(delay/2),
rtptime.JiffiesPerSec,
))
pi.delay = delay / 2
select {
case ch <- pi:
timer.Stop()
case <-timer.C:
}
}
}
}
}
func writeLoop(conn *rtpUpConnection, track *rtpUpTrack, ch <-chan packetIndex) {
defer close(track.writerDone)
buf := make([]byte, packetcache.BufSize)
var packet rtp.Packet
local := make([]downTrack, 0)
firSent := false
writers.write(packet.SequenceNumber, index, delay,
isvideo, packet.Marker)
for {
select {
case action := <-track.localCh:
if action.add {
local = append(local, action.track)
firSent = false
track.mu.Lock()
ntp := track.srNTPTime
rtp := track.srRTPTime
cname := track.cname
track.mu.Unlock()
if ntp != 0 {
action.track.setTimeOffset(ntp, rtp)
}
if cname != "" {
action.track.setCname(cname)
}
} else {
found := false
for i, t := range local {
if t == action.track {
local = append(local[:i],
local[i+1:]...)
found = true
break
}
}
if !found {
log.Printf("Deleting unknown track!")
}
}
case pi, ok := <-ch:
if !ok {
return
}
bytes := track.cache.GetAt(pi.seqno, pi.index, buf)
if bytes == 0 {
continue
}
err := packet.Unmarshal(buf[:bytes])
err := writers.add(action.track, action.add)
if err != nil {
log.Printf("%v", err)
continue
}
var delay time.Duration
if len(local) > 0 {
delay = rtptime.ToDuration(
uint64(pi.delay/uint32(len(local))),
rtptime.JiffiesPerSec,
)
}
kfNeeded := false
for _, l := range local {
err := l.WriteRTP(&packet)
if err != nil {
if err == ErrKeyframeNeeded {
kfNeeded = true
} else if err != io.ErrClosedPipe {
log.Printf("WriteRTP: %v", err)
}
continue
}
l.Accumulate(uint32(bytes))
if delay > 0 {
time.Sleep(delay)
}
}
if kfNeeded {
err := conn.sendFIR(track, !firSent)
if err == ErrUnsupportedFeedback {
err := conn.sendPLI(track)
if err != nil &&
err != ErrUnsupportedFeedback &&
err != ErrRateLimited {
log.Printf("sendPLI: %v", err)
}
} else if err != nil && err != ErrRateLimited {
log.Printf("sendFIR: %v", err)
}
firSent = true
log.Printf("add/remove track: %v", err)
}
default:
}
}
}
......
rtpwriter.go 0 → 100644
View file @ fa29e50f
package main
import (
"errors"
"log"
"time"
"github.com/pion/rtp"
"sfu/packetcache"
"sfu/rtptime"
)
// packetIndex is a request to send a packet from the cache.
type packetIndex struct {
// the packet's seqno
seqno uint16
// the index in the cache
index uint16
// the expected delay until the next packet, in jiffies
delay uint32
}
// An rtpWriterPool is a set of rtpWriters
type rtpWriterPool struct {
conn *rtpUpConnection
track *rtpUpTrack
writers []*rtpWriter
count int
}
// sqrt computes the integer square root
func sqrt(n int) int {
if n < 2 {
return n
}
s := sqrt(n/2) * 2
l := s + 1
if l*l > n {
return s
} else {
return l
}
}
// add adds or removes a track from a writer pool
func (wp *rtpWriterPool) add(track downTrack, add bool) error {
n := 4
if wp.count > 16 {
n = sqrt(wp.count)
}
i := 0
for i < len(wp.writers) {
w := wp.writers[i]
err := w.add(track, add, n)
if err == nil {
if add {
wp.count++
} else {
if wp.count > 0 {
wp.count--
} else {
log.Printf("Negative writer count!")
}
}
return nil
} else if err == ErrWriterDead {
wp.del(wp.writers[i])
} else {
i++
}
}
if add {
writer := newRtpWriter(wp.conn, wp.track)
wp.writers = append(wp.writers, writer)
err := writer.add(track, true, n)
if err == nil {
wp.count++
}
return err
} else {
return errors.New("deleting unknown track")
}
}
// del deletes a writer.
func (wp *rtpWriterPool) del(w *rtpWriter) bool {
for i, ww := range wp.writers {
if ww == w {
close(w.ch)
wp.writers = append(wp.writers[:i], wp.writers[i+1:]...)
return true
}
}
return false
}
// close deletes all writers.
func (wp *rtpWriterPool) close() {
for _, w := range wp.writers {
close(w.ch)
}
wp.writers = nil
wp.count = 0
}
// write writes a packet stored in the packet cache to all local tracks
func (wp *rtpWriterPool) write(seqno uint16, index uint16, delay uint32, isvideo bool, marker bool) {
pi := packetIndex{seqno, index, delay}
var dead []*rtpWriter
for _, w := range wp.writers {
if w.drop > 0 {
// currently dropping
if marker {
// last packet in frame
w.drop = 0
} else {
w.drop--
}
continue
}
select {
case w.ch <- pi:
// all is well
case <-w.done:
// the writer is dead.
dead = append(dead, w)
default:
// the writer is congested
if isvideo {
// drop until the end of the frame
if !marker {
w.drop = 7
}
continue
}
// audio, try again with a delay
d := delay/uint32(2*len(wp.writers))
timer := time.NewTimer(rtptime.ToDuration(
uint64(d), rtptime.JiffiesPerSec,
))
if pi.delay > d {
pi.delay -= d
} else {
pi.delay = 0
}
select {
case w.ch <- pi:
timer.Stop()
case <-w.done:
dead = append(dead, w)
case <-timer.C:
}
}
}
if dead != nil {
for _, d := range dead {
wp.del(d)
}
dead = nil
}
}
var ErrWriterDead = errors.New("writer is dead")
var ErrWriterBusy = errors.New("writer is busy")
var ErrUnknownTrack = errors.New("unknown track")
type writerAction struct {
add bool
track downTrack
maxTracks int
ch chan error
}
// an rtpWriter is a thread writing to a set of tracks.
type rtpWriter struct {
ch chan packetIndex
done chan struct{}
action chan writerAction
// this is not touched by the writer loop, used by the caller
drop int
}
func newRtpWriter(conn *rtpUpConnection, track *rtpUpTrack) *rtpWriter {
writer := &rtpWriter{
ch: make(chan packetIndex, 32),
done: make(chan struct{}),
action: make(chan writerAction, 1),
}
go rtpWriterLoop(writer, conn, track)
return writer
}
// add adds or removes a track from a writer.
func (writer *rtpWriter) add(track downTrack, add bool, max int) error {
ch := make(chan error, 1)
select {
case writer.action <- writerAction{add, track, max, ch}:
select {
case err := <-ch:
return err
case <-writer.done:
return ErrWriterDead
}
case <-writer.done:
return ErrWriterDead
}
}
// rtpWriterLoop is the main loop of an rtpWriter.
func rtpWriterLoop(writer *rtpWriter, conn *rtpUpConnection, track *rtpUpTrack) {
defer close(writer.done)
buf := make([]byte, packetcache.BufSize)
var packet rtp.Packet
local := make([]downTrack, 0)
// reset whenever a new track is inserted
firSent := false
for {
select {
case action := <-writer.action:
if action.add {
if len(local) >= action.maxTracks {
action.ch <- ErrWriterBusy
close(action.ch)
continue
}
local = append(local, action.track)
action.ch <- nil
close(action.ch)
firSent = false
track.mu.Lock()
ntp := track.srNTPTime
rtp := track.srRTPTime
cname := track.cname
track.mu.Unlock()
if ntp != 0 {
action.track.setTimeOffset(ntp, rtp)
}
if cname != "" {
action.track.setCname(cname)
}
} else {
found := false
for i, t := range local {
if t == action.track {
local = append(local[:i],
local[i+1:]...)
found = true
break
}
}
if !found {
action.ch <- ErrUnknownTrack
} else {
action.ch <- nil
}
close(action.ch)
if len(local) == 0 {
return
}
}
case pi, ok := <-writer.ch:
if !ok {
return
}
bytes := track.cache.GetAt(pi.seqno, pi.index, buf)
if bytes == 0 {
continue
}
err := packet.Unmarshal(buf[:bytes])
if err != nil {
continue
}
var delay time.Duration
if len(local) > 0 {
delay = rtptime.ToDuration(
uint64(pi.delay/uint32(len(local))),
rtptime.JiffiesPerSec,
)
}
kfNeeded := false
for _, l := range local {
err := l.WriteRTP(&packet)
if err != nil {
if err == ErrKeyframeNeeded {
kfNeeded = true
}
continue
}
l.Accumulate(uint32(bytes))
if delay > 0 {
time.Sleep(delay)
}
}
if kfNeeded {
err := conn.sendFIR(track, !firSent)
if err == ErrUnsupportedFeedback {
conn.sendPLI(track)
}
firSent = true
}
}
}
}
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