From e111830bc653116100d3052dfbd85cd606cbba89 Mon Sep 17 00:00:00 2001
From: Sina Mahmoodi <itz.s1na@gmail.com>
Date: Thu, 15 Dec 2022 15:07:10 +0100
Subject: [PATCH] eth/tracers: exec block serially for native tracer

Co-authored-by: Martin Holst Swende <martin@swende.se>
---
 eth/tracers/api.go     | 58 +++++++++++++++++++++++++++++++++++++-----
 eth/tracers/js/goja.go |  3 +++
 eth/tracers/tracers.go |  6 +++++
 3 files changed, 60 insertions(+), 7 deletions(-)

diff --git a/eth/tracers/api.go b/eth/tracers/api.go
index 4436d13961f63..a15ec4366de9c 100644
--- a/eth/tracers/api.go
+++ b/eth/tracers/api.go
@@ -593,6 +593,7 @@ func (api *API) traceBlock(ctx context.Context, block *types.Block, config *Trac
 	if block.NumberU64() == 0 {
 		return nil, errors.New("genesis is not traceable")
 	}
+	// Prepare base state
 	parent, err := api.blockByNumberAndHash(ctx, rpc.BlockNumber(block.NumberU64()-1), block.ParentHash())
 	if err != nil {
 		return nil, err
@@ -606,24 +607,68 @@ func (api *API) traceBlock(ctx context.Context, block *types.Block, config *Trac
 		return nil, err
 	}
 	defer release()
+	// JS tracers have high overhead. In this case run a parallel
+	// process that generates states in one thread and traces txes
+	// in separate worker threads.
+	if config.Tracer != nil && *config.Tracer != "" {
+		t, err := New(*config.Tracer, nil, nil)
+		if err != nil {
+			return nil, err
+		}
+		if _, ok := t.(JSTracer); ok {
+			return api.traceBlockParallel(ctx, block, statedb, config)
+		}
+	}
+	// Native tracers have low overhead
+	var (
+		txs       = block.Transactions()
+		blockHash = block.Hash()
+		is158     = api.backend.ChainConfig().IsEIP158(block.Number())
+		blockCtx  = core.NewEVMBlockContext(block.Header(), api.chainContext(ctx), nil)
+		signer    = types.MakeSigner(api.backend.ChainConfig(), block.Number())
+		results   = make([]*txTraceResult, len(txs))
+	)
+	for i, tx := range txs {
+		// Generate the next state snapshot fast without tracing
+		msg, _ := tx.AsMessage(signer, block.BaseFee())
+		txctx := &Context{
+			BlockHash: blockHash,
+			TxIndex:   i,
+			TxHash:    tx.Hash(),
+		}
+		res, err := api.traceTx(ctx, msg, txctx, blockCtx, statedb, config)
+		if err != nil {
+			return nil, err
+		}
+		results[i] = &txTraceResult{Result: res}
+		// Finalize the state so any modifications are written to the trie
+		// Only delete empty objects if EIP158/161 (a.k.a Spurious Dragon) is in effect
+		statedb.Finalise(is158)
+	}
+	return results, nil
+}
 
+// traceBlockParallel is for tracers that have a high overhead (read JS tracers). One thread
+// runs along and executes txes without tracing enabled to generate their prestate.
+// Worker threads take the tasks and the prestate and trace them.
+func (api *API) traceBlockParallel(ctx context.Context, block *types.Block, statedb *state.StateDB, config *TraceConfig) ([]*txTraceResult, error) {
 	// Execute all the transaction contained within the block concurrently
 	var (
-		signer  = types.MakeSigner(api.backend.ChainConfig(), block.Number())
-		txs     = block.Transactions()
-		results = make([]*txTraceResult, len(txs))
-		pend    sync.WaitGroup
+		txs       = block.Transactions()
+		blockHash = block.Hash()
+		blockCtx  = core.NewEVMBlockContext(block.Header(), api.chainContext(ctx), nil)
+		signer    = types.MakeSigner(api.backend.ChainConfig(), block.Number())
+		results   = make([]*txTraceResult, len(txs))
+		pend      sync.WaitGroup
 	)
 	threads := runtime.NumCPU()
 	if threads > len(txs) {
 		threads = len(txs)
 	}
 	jobs := make(chan *txTraceTask, threads)
-	blockHash := block.Hash()
 	for th := 0; th < threads; th++ {
 		pend.Add(1)
 		go func() {
-			blockCtx := core.NewEVMBlockContext(block.Header(), api.chainContext(ctx), nil)
 			defer pend.Done()
 			// Fetch and execute the next transaction trace tasks
 			for task := range jobs {
@@ -645,7 +690,6 @@ func (api *API) traceBlock(ctx context.Context, block *types.Block, config *Trac
 
 	// Feed the transactions into the tracers and return
 	var failed error
-	blockCtx := core.NewEVMBlockContext(block.Header(), api.chainContext(ctx), nil)
 txloop:
 	for i, tx := range txs {
 		// Send the trace task over for execution
diff --git a/eth/tracers/js/goja.go b/eth/tracers/js/goja.go
index 9adfca9fb62a6..ba7f97914e042 100644
--- a/eth/tracers/js/goja.go
+++ b/eth/tracers/js/goja.go
@@ -350,6 +350,9 @@ func (t *jsTracer) Stop(err error) {
 	t.vm.Interrupt(err)
 }
 
+// IsJS returns whether this tracer evaluates JS code.
+func (t *jsTracer) IsJS() bool { return true }
+
 // onError is called anytime the running JS code is interrupted
 // and returns an error. It in turn pings the EVM to cancel its
 // execution.
diff --git a/eth/tracers/tracers.go b/eth/tracers/tracers.go
index 3d2d1256c0914..c84dc758556ba 100644
--- a/eth/tracers/tracers.go
+++ b/eth/tracers/tracers.go
@@ -42,6 +42,12 @@ type Tracer interface {
 	Stop(err error)
 }
 
+// JSTracer is implemented by tracers evaluating JS code.
+type JSTracer interface {
+	Tracer
+	IsJS() bool
+}
+
 type lookupFunc func(string, *Context, json.RawMessage) (Tracer, error)
 
 var (