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[RFC] limiter: smarter perPeerLimit #81

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[RFC] limiter: smarter perPeerLimit #81

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54 changes: 37 additions & 17 deletions limiter.go
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@ import (
peer "github.com/libp2p/go-libp2p-peer"
transport "github.com/libp2p/go-libp2p-transport"
ma "github.com/multiformats/go-multiaddr"
"math"
)

type dialResult struct {
Expand Down Expand Up @@ -52,7 +53,7 @@ type dialLimiter struct {
dialFunc dialfunc

activePerPeer map[peer.ID]int
perPeerLimit int
perPeerLimitMax int
waitingOnPeerLimit map[peer.ID][]*dialJob
}

Expand All @@ -65,13 +66,18 @@ func newDialLimiter(df dialfunc) *dialLimiter {
func newDialLimiterWithParams(df dialfunc, fdLimit, perPeerLimit int) *dialLimiter {
return &dialLimiter{
fdLimit: fdLimit,
perPeerLimit: perPeerLimit,
perPeerLimitMax: perPeerLimit,
waitingOnPeerLimit: make(map[peer.ID][]*dialJob),
activePerPeer: make(map[peer.ID]int),
dialFunc: df,
}
}

func (dl *dialLimiter) perPeerLimit() int {
fdPeerRatio := float64(dl.fdLimit) / float64(dl.fdConsuming + 1)
return int(math.Ceil(math.Min(fdPeerRatio, float64(dl.perPeerLimitMax))))
}

// freeFDToken frees FD token and if there are any schedules another waiting dialJob
// in it's place
func (dl *dialLimiter) freeFDToken() {
Expand All @@ -91,27 +97,41 @@ func (dl *dialLimiter) freeFDToken() {
}
}

func (dl *dialLimiter) updateWaitingPerPeer() {
for p := range dl.activePerPeer {
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These two loops are going to be very CPU heavy.

for {
if dl.activePerPeer[p] >= dl.perPeerLimit() {
break
}

waitlist := dl.waitingOnPeerLimit[p]
if len(waitlist) == 0 {
break
}

next := waitlist[0]
if len(waitlist) == 1 {
delete(dl.waitingOnPeerLimit, p)
} else {
waitlist[0] = nil // clear out memory
dl.waitingOnPeerLimit[p] = waitlist[1:]
}

dl.activePerPeer[p]++

dl.addCheckFdLimit(next)
}
}
}

func (dl *dialLimiter) freePeerToken(dj *dialJob) {
// release tokens in reverse order than we take them
dl.activePerPeer[dj.peer]--
if dl.activePerPeer[dj.peer] == 0 {
delete(dl.activePerPeer, dj.peer)
}

waitlist := dl.waitingOnPeerLimit[dj.peer]
if len(waitlist) > 0 {
next := waitlist[0]
if len(waitlist) == 1 {
delete(dl.waitingOnPeerLimit, next.peer)
} else {
waitlist[0] = nil // clear out memory
dl.waitingOnPeerLimit[next.peer] = waitlist[1:]
}

dl.activePerPeer[next.peer]++ // just kidding, we still want this token

dl.addCheckFdLimit(next)
}
dl.updateWaitingPerPeer()
}

func (dl *dialLimiter) finishedDial(dj *dialJob) {
Expand Down Expand Up @@ -140,7 +160,7 @@ func (dl *dialLimiter) addCheckFdLimit(dj *dialJob) {
}

func (dl *dialLimiter) addCheckPeerLimit(dj *dialJob) {
if dl.activePerPeer[dj.peer] >= dl.perPeerLimit {
if dl.activePerPeer[dj.peer] >= dl.perPeerLimit() {
wlist := dl.waitingOnPeerLimit[dj.peer]
dl.waitingOnPeerLimit[dj.peer] = append(wlist, dj)
return
Expand Down