cmd, core, params: dynamic gas ceiling on heavy blocks

cmd/geth/main.go

@@ -150,6 +150,7 @@ participating.
 		utils.MiningGPUFlag,
 		utils.AutoDAGFlag,
 		utils.TargetGasLimitFlag,
+		utils.BlockTimeLimitFlag,
 		utils.NATFlag,
 		utils.NatspecEnabledFlag,
 		utils.NoDiscoverFlag,

cmd/geth/usage.go

@@ -126,6 +126,7 @@ var AppHelpFlagGroups = []flagGroup{
 			utils.AutoDAGFlag,
 			utils.EtherbaseFlag,
 			utils.TargetGasLimitFlag,
+			utils.BlockTimeLimitFlag,
 			utils.GasPriceFlag,
 			utils.ExtraDataFlag,
 		},

cmd/utils/flags.go

@@ -180,9 +180,14 @@ var (
 	}
 	TargetGasLimitFlag = cli.StringFlag{
 		Name:  "targetgaslimit",
-		Usage: "Target gas limit sets the artificial target gas floor for the blocks to mine",
+		Usage: "Sets the artificial target gas floor for the blocks to mine",
 		Value: params.GenesisGasLimit.String(),
 	}
+	BlockTimeLimitFlag = cli.IntFlag{
+		Name:  "blocktimelimit",
+		Usage: "Time limit for processing a block after which to halve the hard gas limit",
+		Value: 5,
+	}
 	AutoDAGFlag = cli.BoolFlag{
 		Name:  "autodag",
 		Usage: "Enable automatic DAG pregeneration",
@@ -746,6 +751,8 @@ func SetupNetwork(ctx *cli.Context) {
 		core.ExpDiffPeriod = big.NewInt(math.MaxInt64)
 	}
 	params.TargetGasLimit = common.String2Big(ctx.GlobalString(TargetGasLimitFlag.Name))
+	params.CurrentGasCeil.Set(params.TargetGasLimit)
+	params.BlockTimeLimit = time.Duration(ctx.GlobalInt(BlockTimeLimitFlag.Name)) * time.Second
 }
 
 // MustMakeChainConfig reads the chain configuration from the database in ctx.Datadir.

core/block_validator.go

@@ -364,7 +364,6 @@ func CalcGasLimit(parent *types.Block) *big.Int {
 	*/
 	gl := new(big.Int).Sub(parent.GasLimit(), decay)
 	gl = gl.Add(gl, contrib)
-	gl.Set(common.BigMax(gl, params.MinGasLimit))
 
 	// however, if we're now below the target (TargetGasLimit) we increase the
 	// limit as much as we can (parentGasLimit / 1024 -1)
@@ -372,5 +371,15 @@ func CalcGasLimit(parent *types.Block) *big.Int {
 		gl.Add(parent.GasLimit(), decay)
 		gl.Set(common.BigMin(gl, params.TargetGasLimit))
 	}
+	// If the gas limit performance ceiling is exceeded, mandatorilly decrease
+	params.CurrentGasCeilLock.Lock()
+	if gl.Cmp(params.CurrentGasCeil) > 0 {
+		gl.Sub(parent.GasLimit(), decay)
+		gl.Set(common.BigMax(gl, params.CurrentGasCeil))
+	}
+	params.CurrentGasCeilLock.Unlock()
+
+	// Make sure we never go below the minimum gas limit
+	gl.Set(common.BigMax(gl, params.MinGasLimit))
 	return gl
 }

core/blockchain.go

@@ -38,6 +38,7 @@ import (
 	"github.com/ethereum/go-ethereum/logger"
 	"github.com/ethereum/go-ethereum/logger/glog"
 	"github.com/ethereum/go-ethereum/metrics"
+	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/pow"
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/ethereum/go-ethereum/trie"
@@ -977,12 +978,24 @@ func (self *BlockChain) InsertChain(chain types.Blocks) (int, error) {
 			events = append(events, ChainSplitEvent{block, logs})
 		}
 		stats.processed++
+
+		// Update the current gas limit (mining only) based on import times
+		params.CurrentGasCeilLock.Lock()
+		if time.Since(bstart) > params.BlockTimeLimit {
+			ceil := new(big.Int).Div(params.CurrentGasCeil, params.CurrentGasCeilCutDiv)
+			params.CurrentGasCeil.Set(common.BigMax(ceil, params.MinGasLimit))
+		} else {
+			ceil := new(big.Int).Add(params.CurrentGasCeil, new(big.Int).Div(params.CurrentGasCeil, params.CurrentGasCeilIncDiv))
+			limit := new(big.Int).Mul(chain[i].GasLimit(), big.NewInt(2))
+			params.CurrentGasCeil.Set(common.BigMin(ceil, limit))
+		}
+		glog.V(logger.Debug).Infof("block gas ceiling changed to %v", params.CurrentGasCeil)
+		params.CurrentGasCeilLock.Unlock()
 	}
 
 	if (stats.queued > 0 || stats.processed > 0 || stats.ignored > 0) && bool(glog.V(logger.Info)) {
-		tend := time.Since(tstart)
 		start, end := chain[0], chain[len(chain)-1]
-		glog.Infof("imported %d block(s) (%d queued %d ignored) including %d txs in %v. #%v [%x / %x]\n", stats.processed, stats.queued, stats.ignored, txcount, tend, end.Number(), start.Hash().Bytes()[:4], end.Hash().Bytes()[:4])
+		glog.Infof("imported %d block(s) (%d queued %d ignored) including %d txs in %v. #%v [%x / %x]\n", stats.processed, stats.queued, stats.ignored, txcount, time.Since(tstart), end.Number(), start.Hash().Bytes()[:4], end.Hash().Bytes()[:4])
 	}
 	go self.postChainEvents(events, coalescedLogs)
 

params/miner_strategy.go

@@ -0,0 +1,35 @@
+// Copyright 2016 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package params
+
+import (
+	"math/big"
+	"sync"
+	"time"
+)
+
+var (
+	GenesisGasLimit = big.NewInt(4712388)               // Gas limit of the Genesis block.
+	TargetGasLimit  = new(big.Int).Set(GenesisGasLimit) // The artificial target
+	BlockTimeLimit  = 5 * time.Second                   // Block processing time limit to reduce gas after
+
+	// Temp hack to get a dynamic gas limit in palace (clean up!!!)
+	CurrentGasCeil       = new(big.Int).Set(GenesisGasLimit)
+	CurrentGasCeilCutDiv = big.NewInt(2)
+	CurrentGasCeilIncDiv = new(big.Int).Set(GasLimitBoundDivisor)
+	CurrentGasCeilLock   sync.Mutex
+)

params/protocol_params.go

@@ -39,10 +39,7 @@ var (
 	CallStipend            = big.NewInt(2300)   // Free gas given at beginning of call.
 	EcrecoverGas           = big.NewInt(3000)   //
 	Sha256WordGas          = big.NewInt(12)     //
-
-	MinGasLimit     = big.NewInt(5000)                  // Minimum the gas limit may ever be.
-	GenesisGasLimit = big.NewInt(4712388)               // Gas limit of the Genesis block.
-	TargetGasLimit  = new(big.Int).Set(GenesisGasLimit) // The artificial target
+	MinGasLimit            = big.NewInt(5000)   // Minimum the gas limit may ever be.
 
 	Sha3Gas              = big.NewInt(30)     // Once per SHA3 operation.
 	Sha256Gas            = big.NewInt(60)     //