Check HeadState First (#4830)

* easy optimization
* Merge refs/heads/master into easyOptimization
* cache miss

beacon-chain/blockchain/process_attestation_helpers.go

@@ -1,6 +1,7 @@
 package blockchain
 
 import (
+	"bytes"
 	"context"
 	"fmt"
 
@@ -28,6 +29,24 @@ func (s *Service) getAttPreState(ctx context.Context, c *ethpb.Checkpoint) (*sta
 		return cachedState, nil
 	}
 
+	headRoot, err := s.HeadRoot(ctx)
+	if err != nil {
+		return nil, errors.Wrapf(err, "could not get head root")
+	}
+	if bytes.Equal(headRoot, c.Root) {
+		st, err := s.HeadState(ctx)
+		if err != nil {
+			return nil, errors.Wrapf(err, "could not get head state")
+		}
+		if err := s.checkpointState.AddCheckpointState(&cache.CheckpointState{
+			Checkpoint: c,
+			State:      st.Copy(),
+		}); err != nil {
+			return nil, errors.Wrap(err, "could not saved checkpoint state to cache")
+		}
+		return st, nil
+	}
+
 	baseState, err := s.beaconDB.State(ctx, bytesutil.ToBytes32(c.Root))
 	if err != nil {
 		return nil, errors.Wrapf(err, "could not get pre state for slot %d", helpers.StartSlot(c.Epoch))

beacon-chain/blockchain/process_block_helpers.go

@@ -73,6 +73,13 @@ func (s *Service) verifyBlkPreState(ctx context.Context, b *ethpb.BeaconBlock) (
 		}
 		return preState.Copy(), nil
 	}
+	headRoot, err := s.HeadRoot(ctx)
+	if err != nil {
+		return nil, errors.Wrapf(err, "could not get head root")
+	}
+	if bytes.Equal(headRoot, b.ParentRoot) {
+		return s.HeadState(ctx)
+	}
 
 	preState, err := s.beaconDB.State(ctx, bytesutil.ToBytes32(b.ParentRoot))
 	if err != nil {