Only process attestations and update head once per slot

beacon-chain/blockchain/head.go

@@ -45,9 +45,10 @@ func (s *Service) UpdateAndSaveHeadWithBalances(ctx context.Context) error {
 
 // This defines the current chain service's view of head.
 type head struct {
-	root  [32]byte                             // current head root.
-	block interfaces.ReadOnlySignedBeaconBlock // current head block.
-	state state.BeaconState                    // current head state.
+	root     [32]byte                             // current head root.
+	block    interfaces.ReadOnlySignedBeaconBlock // current head block.
+	state    state.BeaconState                    // current head state.
+	lastTick primitives.Slot
 }
 
 // This saves head info to the local service cache, it also saves the
@@ -251,6 +252,12 @@ func (s *Service) headRoot() [32]byte {
 	return s.head.root
 }
 
+// This returns the last slot where we have processed attestations
+// This is a lock free version
+func (s *Service) lastTick() primitives.Slot {
+	return s.head.lastTick
+}
+
 // This returns the head block.
 // It does a full copy on head block for immutability.
 // This is a lock free version.

beacon-chain/blockchain/receive_attestation.go

@@ -120,6 +120,13 @@ func (s *Service) spawnProcessAttestationsRoutine(stateFeed *event.Feed) {
 // The caller of this function MUST hold a lock in forkchoice
 func (s *Service) UpdateHead(ctx context.Context, proposingSlot primitives.Slot) {
 	start := time.Now()
+	// Only update head once per slot at the beginning of the slot
+	s.headLock.RLock()
+	lastTick := s.lastTick()
+	s.headLock.RUnlock()
+	if lastTick >= proposingSlot && proposingSlot == s.CurrentSlot() {
+		return
+	}
 
 	// This function is only called at 10 seconds or 0 seconds into the slot
 	disparity := params.BeaconNetworkConfig().MaximumGossipClockDisparity
@@ -127,9 +134,12 @@ func (s *Service) UpdateHead(ctx context.Context, proposingSlot primitives.Slot)
 		disparity += reorgLateBlockCountAttestations
 	}
 	s.processAttestations(ctx, disparity)
-
 	processAttsElapsedTime.Observe(float64(time.Since(start).Milliseconds()))
 
+	s.headLock.Lock()
+	s.head.lastTick = proposingSlot
+	s.headLock.Unlock()
+
 	start = time.Now()
 	newHeadRoot, err := s.cfg.ForkChoiceStore.Head(ctx)
 	if err != nil {