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Make rxQueue lock-free using an atomic counter ring buffer.

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This commit is contained in:
Adam Ierymenko 2017-08-08 13:21:10 -07:00
parent 7e6598e9ca
commit e3cf756785
3 changed files with 33 additions and 39 deletions
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9
node/AtomicCounter.hpp
View File

@ -47,6 +47,15 @@ public:
_v = 0;
}
inline int load() const
{
#ifdef __GNUC__
return __sync_or_and_fetch(&_v,0);
#else
return _v.load();
#endif
}
inline int operator++()
{
#ifdef __GNUC__

36
node/Switch.cpp
View File

@ -120,10 +120,8 @@ void Switch::onRemotePacket(void *tPtr,const int64_t localSocket,const InetAddre
// Total fragments must be more than 1, otherwise why are we
// seeing a Packet::Fragment?
Mutex::Lock _l(_rxQueue_m);
RXQueueEntry *const rq = _findRXQueueEntry(now,fragmentPacketId);
if ((!rq->timestamp)||(rq->packetId != fragmentPacketId)) {
RXQueueEntry *const rq = _findRXQueueEntry(fragmentPacketId);
if (rq->packetId != fragmentPacketId) {
// No packet found, so we received a fragment without its head.
rq->timestamp = now;
@ -250,10 +248,8 @@ void Switch::onRemotePacket(void *tPtr,const int64_t localSocket,const InetAddre
((uint64_t)reinterpret_cast<const uint8_t *>(data)[7])
);
Mutex::Lock _l(_rxQueue_m);
RXQueueEntry *const rq = _findRXQueueEntry(now,packetId);
if ((!rq->timestamp)||(rq->packetId != packetId)) {
RXQueueEntry *const rq = _findRXQueueEntry(packetId);
if (rq->packetId != packetId) {
// If we have no other fragments yet, create an entry and save the head
rq->timestamp = now;
@ -286,14 +282,7 @@ void Switch::onRemotePacket(void *tPtr,const int64_t localSocket,const InetAddre
// Packet is unfragmented, so just process it
IncomingPacket packet(data,len,path,now);
if (!packet.tryDecode(RR,tPtr)) {
Mutex::Lock _l(_rxQueue_m);
RXQueueEntry *rq = &(_rxQueue[ZT_RX_QUEUE_SIZE - 1]);
unsigned long i = ZT_RX_QUEUE_SIZE - 1;
while ((i)&&(rq->timestamp)) {
RXQueueEntry *tmp = &(_rxQueue[--i]);
if (tmp->timestamp < rq->timestamp)
rq = tmp;
}
RXQueueEntry *const rq = _nextRXQueueEntry();
rq->timestamp = now;
rq->packetId = packet.packetId();
rq->frag0 = packet;
@ -590,15 +579,12 @@ void Switch::doAnythingWaitingForPeer(void *tPtr,const SharedPtr<Peer> &peer)
_outstandingWhoisRequests.erase(peer->address());
}
{ // finish processing any packets waiting on peer's public key / identity
Mutex::Lock _l(_rxQueue_m);
unsigned long i = ZT_RX_QUEUE_SIZE;
while (i) {
RXQueueEntry *rq = &(_rxQueue[--i]);
if ((rq->timestamp)&&(rq->complete)) {
if (rq->frag0.tryDecode(RR,tPtr))
rq->timestamp = 0;
}
// finish processing any packets waiting on peer's public key / identity
for(unsigned int ptr=0;ptr<ZT_RX_QUEUE_SIZE;++ptr) {
RXQueueEntry *const rq = &(_rxQueue[ptr]);
if ((rq->timestamp)&&(rq->complete)) {
if (rq->frag0.tryDecode(RR,tPtr))
rq->timestamp = 0;
}
}

27
node/Switch.hpp
View File

@ -169,25 +169,24 @@ private:
bool complete; // if true, packet is complete
};
RXQueueEntry _rxQueue[ZT_RX_QUEUE_SIZE];
Mutex _rxQueue_m;
AtomicCounter _rxQueuePtr;
/* Returns the matching or oldest entry. Caller must check timestamp and
* packet ID to determine which. */
inline RXQueueEntry *_findRXQueueEntry(uint64_t now,uint64_t packetId)
// Returns matching or next available RX queue entry
inline RXQueueEntry *_findRXQueueEntry(uint64_t packetId)
{
RXQueueEntry *rq;
RXQueueEntry *oldest = &(_rxQueue[ZT_RX_QUEUE_SIZE - 1]);
unsigned long i = ZT_RX_QUEUE_SIZE;
while (i) {
rq = &(_rxQueue[--i]);
unsigned int ptr = static_cast<unsigned int>(_rxQueuePtr.load());
for(unsigned int k=0;k<ZT_RX_QUEUE_SIZE;++k) {
RXQueueEntry *rq = &(_rxQueue[--ptr % ZT_RX_QUEUE_SIZE]);
if ((rq->packetId == packetId)&&(rq->timestamp))
return rq;
if ((now - rq->timestamp) >= ZT_RX_QUEUE_EXPIRE)
rq->timestamp = 0;
if (rq->timestamp < oldest->timestamp)
oldest = rq;
}
return oldest;
return &(_rxQueue[static_cast<unsigned int>(++_rxQueuePtr) % ZT_RX_QUEUE_SIZE]);
}
// Returns next RX queue entry in ring buffer and increments ring counter
inline RXQueueEntry *_nextRXQueueEntry()
{
return &(_rxQueue[static_cast<unsigned int>(++_rxQueuePtr) % ZT_RX_QUEUE_SIZE]);
}
// ZeroTier-layer TX queue entry