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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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27
node/Switch.hpp
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@ -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