automatic DAG pregeneration for smooth epoch transitions

- backend: AutoDAG bool flag passed from cli/eth.Config to ethereum, autoDAG loop started if true
- backend: autoDAG loop start/stop, remove previous DAG
- cli: AutoDAG bool flag, off by default, but automatically ON if mining
- admin jsre: add startAutoDAG stopAutoDAG and makeDAG in miner section
- switch on/off DAG autogeneration when miner started/stopped on console

cmd/geth/admin.go

@@ -8,6 +8,7 @@ import (
 	"strconv"
 	"time"
 
+	"github.com/ethereum/ethash"
 	"github.com/ethereum/go-ethereum/accounts"
 	"github.com/ethereum/go-ethereum/cmd/utils"
 	"github.com/ethereum/go-ethereum/common"
@@ -73,6 +74,9 @@ func (js *jsre) adminBindings() {
 	miner.Set("hashrate", js.hashrate)
 	miner.Set("setExtra", js.setExtra)
 	miner.Set("setGasPrice", js.setGasPrice)
+	miner.Set("startAutoDAG", js.startAutoDAG)
+	miner.Set("stopAutoDAG", js.stopAutoDAG)
+	miner.Set("makeDAG", js.makeDAG)
 
 	admin.Set("debug", struct{}{})
 	t, _ = admin.Get("debug")
@@ -278,6 +282,30 @@ func (js *jsre) hashrate(otto.FunctionCall) otto.Value {
 	return js.re.ToVal(js.ethereum.Miner().HashRate())
 }
 
+func (js *jsre) makeDAG(call otto.FunctionCall) otto.Value {
+	blockNumber, err := call.Argument(1).ToInteger()
+	if err != nil {
+		fmt.Println(err)
+		return otto.FalseValue()
+	}
+
+	err = ethash.MakeDAG(uint64(blockNumber), "")
+	if err != nil {
+		return otto.FalseValue()
+	}
+	return otto.TrueValue()
+}
+
+func (js *jsre) startAutoDAG(otto.FunctionCall) otto.Value {
+	js.ethereum.StartAutoDAG()
+	return otto.TrueValue()
+}
+
+func (js *jsre) stopAutoDAG(otto.FunctionCall) otto.Value {
+	js.ethereum.StopAutoDAG()
+	return otto.TrueValue()
+}
+
 func (js *jsre) backtrace(call otto.FunctionCall) otto.Value {
 	tracestr, err := call.Argument(0).ToString()
 	if err != nil {
@@ -316,6 +344,9 @@ func (js *jsre) startMining(call otto.FunctionCall) otto.Value {
 		threads = int64(js.ethereum.MinerThreads)
 	}
 
+	// switch on DAG autogeneration when miner starts
+	js.ethereum.StartAutoDAG()
+
 	err = js.ethereum.StartMining(int(threads))
 	if err != nil {
 		fmt.Println(err)
@@ -327,6 +358,7 @@ func (js *jsre) startMining(call otto.FunctionCall) otto.Value {
 
 func (js *jsre) stopMining(call otto.FunctionCall) otto.Value {
 	js.ethereum.StopMining()
+	js.ethereum.StopAutoDAG()
 	return otto.TrueValue()
 }
 

cmd/geth/main.go

@@ -117,7 +117,7 @@ passwordfile as argument containing the wallet password in plaintext.
 Manage accounts lets you create new accounts, list all existing accounts,
 import a private key into a new account.
 
-'account help' shows a list of subcommands or help for one subcommand.
+'            help' shows a list of subcommands or help for one subcommand.
 
 It supports interactive mode, when you are prompted for password as well as
 non-interactive mode where passwords are supplied via a given password file.
@@ -257,6 +257,7 @@ JavaScript API. See https://github.com/ethereum/go-ethereum/wiki/Javascipt-Conso
 		utils.GasPriceFlag,
 		utils.MinerThreadsFlag,
 		utils.MiningEnabledFlag,
+		utils.AutoDAGFlag,
 		utils.NATFlag,
 		utils.NatspecEnabledFlag,
 		utils.NodeKeyFileFlag,