cmd, consensus: add option to disable mmap for DAG caches/datasets (#20484)

* cmd, consensus: add option to disable mmap for DAG caches/datasets

* consensus: add benchmarks for mmap with/with lock

cmd/geth/main.go

@@ -74,9 +74,11 @@ var (
 		utils.EthashCacheDirFlag,
 		utils.EthashCachesInMemoryFlag,
 		utils.EthashCachesOnDiskFlag,
+		utils.EthashCachesLockMmapFlag,
 		utils.EthashDatasetDirFlag,
 		utils.EthashDatasetsInMemoryFlag,
 		utils.EthashDatasetsOnDiskFlag,
+		utils.EthashDatasetsLockMmapFlag,
 		utils.TxPoolLocalsFlag,
 		utils.TxPoolNoLocalsFlag,
 		utils.TxPoolJournalFlag,

cmd/geth/retesteth.go

@@ -390,8 +390,10 @@ func (api *RetestethAPI) SetChainParams(ctx context.Context, chainParams ChainPa
 			CacheDir:         "ethash",
 			CachesInMem:      2,
 			CachesOnDisk:     3,
+			CachesLockMmap:   false,
 			DatasetsInMem:    1,
 			DatasetsOnDisk:   2,
+			DatasetsLockMmap: false,
 		}, nil, false)
 	default:
 		return false, fmt.Errorf("unrecognised seal engine: %s", chainParams.SealEngine)

cmd/geth/usage.go

@@ -109,9 +109,11 @@ var AppHelpFlagGroups = []flagGroup{
 			utils.EthashCacheDirFlag,
 			utils.EthashCachesInMemoryFlag,
 			utils.EthashCachesOnDiskFlag,
+			utils.EthashCachesLockMmapFlag,
 			utils.EthashDatasetDirFlag,
 			utils.EthashDatasetsInMemoryFlag,
 			utils.EthashDatasetsOnDiskFlag,
+			utils.EthashDatasetsLockMmapFlag,
 		},
 	},
 	{

cmd/utils/flags.go

@@ -305,6 +305,10 @@ var (
 		Usage: "Number of recent ethash caches to keep on disk (16MB each)",
 		Value: eth.DefaultConfig.Ethash.CachesOnDisk,
 	}
+	EthashCachesLockMmapFlag = cli.BoolFlag{
+		Name:  "ethash.cacheslockmmap",
+		Usage: "Lock memory maps of recent ethash caches",
+	}
 	EthashDatasetDirFlag = DirectoryFlag{
 		Name:  "ethash.dagdir",
 		Usage: "Directory to store the ethash mining DAGs",
@@ -320,6 +324,10 @@ var (
 		Usage: "Number of recent ethash mining DAGs to keep on disk (1+GB each)",
 		Value: eth.DefaultConfig.Ethash.DatasetsOnDisk,
 	}
+	EthashDatasetsLockMmapFlag = cli.BoolFlag{
+		Name:  "ethash.dagslockmmap",
+		Usage: "Lock memory maps for recent ethash mining DAGs",
+	}
 	// Transaction pool settings
 	TxPoolLocalsFlag = cli.StringFlag{
 		Name:  "txpool.locals",
@@ -1306,12 +1314,18 @@ func setEthash(ctx *cli.Context, cfg *eth.Config) {
 	if ctx.GlobalIsSet(EthashCachesOnDiskFlag.Name) {
 		cfg.Ethash.CachesOnDisk = ctx.GlobalInt(EthashCachesOnDiskFlag.Name)
 	}
+	if ctx.GlobalIsSet(EthashCachesLockMmapFlag.Name) {
+		cfg.Ethash.CachesLockMmap = ctx.GlobalBool(EthashCachesLockMmapFlag.Name)
+	}
 	if ctx.GlobalIsSet(EthashDatasetsInMemoryFlag.Name) {
 		cfg.Ethash.DatasetsInMem = ctx.GlobalInt(EthashDatasetsInMemoryFlag.Name)
 	}
 	if ctx.GlobalIsSet(EthashDatasetsOnDiskFlag.Name) {
 		cfg.Ethash.DatasetsOnDisk = ctx.GlobalInt(EthashDatasetsOnDiskFlag.Name)
 	}
+	if ctx.GlobalIsSet(EthashDatasetsLockMmapFlag.Name) {
+		cfg.Ethash.DatasetsLockMmap = ctx.GlobalBool(EthashDatasetsLockMmapFlag.Name)
+	}
 }
 
 func setMiner(ctx *cli.Context, cfg *miner.Config) {
@@ -1724,9 +1738,11 @@ func MakeChain(ctx *cli.Context, stack *node.Node) (chain *core.BlockChain, chai
 				CacheDir:         stack.ResolvePath(eth.DefaultConfig.Ethash.CacheDir),
 				CachesInMem:      eth.DefaultConfig.Ethash.CachesInMem,
 				CachesOnDisk:     eth.DefaultConfig.Ethash.CachesOnDisk,
+				CachesLockMmap:   eth.DefaultConfig.Ethash.CachesLockMmap,
 				DatasetDir:       stack.ResolvePath(eth.DefaultConfig.Ethash.DatasetDir),
 				DatasetsInMem:    eth.DefaultConfig.Ethash.DatasetsInMem,
 				DatasetsOnDisk:   eth.DefaultConfig.Ethash.DatasetsOnDisk,
+				DatasetsLockMmap: eth.DefaultConfig.Ethash.DatasetsLockMmap,
 			}, nil, false)
 		}
 	}

consensus/ethash/algorithm_test.go

@@ -729,7 +729,7 @@ func TestConcurrentDiskCacheGeneration(t *testing.T) {
 
 		go func(idx int) {
 			defer pend.Done()
-			ethash := New(Config{cachedir, 0, 1, "", 0, 0, ModeNormal, nil}, nil, false)
+			ethash := New(Config{cachedir, 0, 1, false, "", 0, 0, false, ModeNormal, nil}, nil, false)
 			defer ethash.Close()
 			if err := ethash.VerifySeal(nil, block.Header()); err != nil {
 				t.Errorf("proc %d: block verification failed: %v", idx, err)
@@ -787,3 +787,28 @@ func BenchmarkHashimotoFullSmall(b *testing.B) {
 		hashimotoFull(dataset, hash, 0)
 	}
 }
+
+func benchmarkHashimotoFullMmap(b *testing.B, name string, lock bool) {
+	b.Run(name, func(b *testing.B) {
+		tmpdir, err := ioutil.TempDir("", "ethash-test")
+		if err != nil {
+			b.Fatal(err)
+		}
+		defer os.RemoveAll(tmpdir)
+
+		d := &dataset{epoch: 0}
+		d.generate(tmpdir, 1, lock, false)
+		var hash [common.HashLength]byte
+		b.ResetTimer()
+		for i := 0; i < b.N; i++ {
+			binary.PutVarint(hash[:], int64(i))
+			hashimotoFull(d.dataset, hash[:], 0)
+		}
+	})
+}
+
+// Benchmarks the full verification performance for mmap
+func BenchmarkHashimotoFullMmap(b *testing.B) {
+	benchmarkHashimotoFullMmap(b, "WithLock", true)
+	benchmarkHashimotoFullMmap(b, "WithoutLock", false)
+}

consensus/ethash/ethash.go

@@ -48,7 +48,7 @@ var (
 	two256 = new(big.Int).Exp(big.NewInt(2), big.NewInt(256), big.NewInt(0))
 
 	// sharedEthash is a full instance that can be shared between multiple users.
-	sharedEthash = New(Config{"", 3, 0, "", 1, 0, ModeNormal, nil}, nil, false)
+	sharedEthash = New(Config{"", 3, 0, false, "", 1, 0, false, ModeNormal, nil}, nil, false)
 
 	// algorithmRevision is the data structure version used for file naming.
 	algorithmRevision = 23
@@ -65,7 +65,7 @@ func isLittleEndian() bool {
 }
 
 // memoryMap tries to memory map a file of uint32s for read only access.
-func memoryMap(path string) (*os.File, mmap.MMap, []uint32, error) {
+func memoryMap(path string, lock bool) (*os.File, mmap.MMap, []uint32, error) {
 	file, err := os.OpenFile(path, os.O_RDONLY, 0644)
 	if err != nil {
 		return nil, nil, nil, err
@@ -82,6 +82,13 @@ func memoryMap(path string) (*os.File, mmap.MMap, []uint32, error) {
 			return nil, nil, nil, ErrInvalidDumpMagic
 		}
 	}
+	if lock {
+		if err := mem.Lock(); err != nil {
+			mem.Unmap()
+			file.Close()
+			return nil, nil, nil, err
+		}
+	}
 	return file, mem, buffer[len(dumpMagic):], err
 }
 
@@ -107,7 +114,7 @@ func memoryMapFile(file *os.File, write bool) (mmap.MMap, []uint32, error) {
 // memoryMapAndGenerate tries to memory map a temporary file of uint32s for write
 // access, fill it with the data from a generator and then move it into the final
 // path requested.
-func memoryMapAndGenerate(path string, size uint64, generator func(buffer []uint32)) (*os.File, mmap.MMap, []uint32, error) {
+func memoryMapAndGenerate(path string, size uint64, lock bool, generator func(buffer []uint32)) (*os.File, mmap.MMap, []uint32, error) {
 	// Ensure the data folder exists
 	if err := os.MkdirAll(filepath.Dir(path), 0755); err != nil {
 		return nil, nil, nil, err
@@ -142,7 +149,7 @@ func memoryMapAndGenerate(path string, size uint64, generator func(buffer []uint
 	if err := os.Rename(temp, path); err != nil {
 		return nil, nil, nil, err
 	}
-	return memoryMap(path)
+	return memoryMap(path, lock)
 }
 
 // lru tracks caches or datasets by their last use time, keeping at most N of them.
@@ -213,7 +220,7 @@ func newCache(epoch uint64) interface{} {
 }
 
 // generate ensures that the cache content is generated before use.
-func (c *cache) generate(dir string, limit int, test bool) {
+func (c *cache) generate(dir string, limit int, lock bool, test bool) {
 	c.once.Do(func() {
 		size := cacheSize(c.epoch*epochLength + 1)
 		seed := seedHash(c.epoch*epochLength + 1)
@@ -240,7 +247,7 @@ func (c *cache) generate(dir string, limit int, test bool) {
 
 		// Try to load the file from disk and memory map it
 		var err error
-		c.dump, c.mmap, c.cache, err = memoryMap(path)
+		c.dump, c.mmap, c.cache, err = memoryMap(path, lock)
 		if err == nil {
 			logger.Debug("Loaded old ethash cache from disk")
 			return
@@ -248,7 +255,7 @@ func (c *cache) generate(dir string, limit int, test bool) {
 		logger.Debug("Failed to load old ethash cache", "err", err)
 
 		// No previous cache available, create a new cache file to fill
-		c.dump, c.mmap, c.cache, err = memoryMapAndGenerate(path, size, func(buffer []uint32) { generateCache(buffer, c.epoch, seed) })
+		c.dump, c.mmap, c.cache, err = memoryMapAndGenerate(path, size, lock, func(buffer []uint32) { generateCache(buffer, c.epoch, seed) })
 		if err != nil {
 			logger.Error("Failed to generate mapped ethash cache", "err", err)
 
@@ -290,7 +297,7 @@ func newDataset(epoch uint64) interface{} {
 }
 
 // generate ensures that the dataset content is generated before use.
-func (d *dataset) generate(dir string, limit int, test bool) {
+func (d *dataset) generate(dir string, limit int, lock bool, test bool) {
 	d.once.Do(func() {
 		// Mark the dataset generated after we're done. This is needed for remote
 		defer atomic.StoreUint32(&d.done, 1)
@@ -326,7 +333,7 @@ func (d *dataset) generate(dir string, limit int, test bool) {
 
 		// Try to load the file from disk and memory map it
 		var err error
-		d.dump, d.mmap, d.dataset, err = memoryMap(path)
+		d.dump, d.mmap, d.dataset, err = memoryMap(path, lock)
 		if err == nil {
 			logger.Debug("Loaded old ethash dataset from disk")
 			return
@@ -337,7 +344,7 @@ func (d *dataset) generate(dir string, limit int, test bool) {
 		cache := make([]uint32, csize/4)
 		generateCache(cache, d.epoch, seed)
 
-		d.dump, d.mmap, d.dataset, err = memoryMapAndGenerate(path, dsize, func(buffer []uint32) { generateDataset(buffer, d.epoch, cache) })
+		d.dump, d.mmap, d.dataset, err = memoryMapAndGenerate(path, dsize, lock, func(buffer []uint32) { generateDataset(buffer, d.epoch, cache) })
 		if err != nil {
 			logger.Error("Failed to generate mapped ethash dataset", "err", err)
 
@@ -372,13 +379,13 @@ func (d *dataset) finalizer() {
 // MakeCache generates a new ethash cache and optionally stores it to disk.
 func MakeCache(block uint64, dir string) {
 	c := cache{epoch: block / epochLength}
-	c.generate(dir, math.MaxInt32, false)
+	c.generate(dir, math.MaxInt32, false, false)
 }
 
 // MakeDataset generates a new ethash dataset and optionally stores it to disk.
 func MakeDataset(block uint64, dir string) {
 	d := dataset{epoch: block / epochLength}
-	d.generate(dir, math.MaxInt32, false)
+	d.generate(dir, math.MaxInt32, false, false)
 }
 
 // Mode defines the type and amount of PoW verification an ethash engine makes.
@@ -397,9 +404,11 @@ type Config struct {
 	CacheDir         string
 	CachesInMem      int
 	CachesOnDisk     int
+	CachesLockMmap   bool
 	DatasetDir       string
 	DatasetsInMem    int
 	DatasetsOnDisk   int
+	DatasetsLockMmap bool
 	PowMode          Mode
 
 	Log log.Logger `toml:"-"`
@@ -549,12 +558,12 @@ func (ethash *Ethash) cache(block uint64) *cache {
 	current := currentI.(*cache)
 
 	// Wait for generation finish.
-	current.generate(ethash.config.CacheDir, ethash.config.CachesOnDisk, ethash.config.PowMode == ModeTest)
+	current.generate(ethash.config.CacheDir, ethash.config.CachesOnDisk, ethash.config.CachesLockMmap, ethash.config.PowMode == ModeTest)
 
 	// If we need a new future cache, now's a good time to regenerate it.
 	if futureI != nil {
 		future := futureI.(*cache)
-		go future.generate(ethash.config.CacheDir, ethash.config.CachesOnDisk, ethash.config.PowMode == ModeTest)
+		go future.generate(ethash.config.CacheDir, ethash.config.CachesOnDisk, ethash.config.CachesLockMmap, ethash.config.PowMode == ModeTest)
 	}
 	return current
 }
@@ -574,20 +583,20 @@ func (ethash *Ethash) dataset(block uint64, async bool) *dataset {
 	// If async is specified, generate everything in a background thread
 	if async && !current.generated() {
 		go func() {
-			current.generate(ethash.config.DatasetDir, ethash.config.DatasetsOnDisk, ethash.config.PowMode == ModeTest)
+			current.generate(ethash.config.DatasetDir, ethash.config.DatasetsOnDisk, ethash.config.DatasetsLockMmap, ethash.config.PowMode == ModeTest)
 
 			if futureI != nil {
 				future := futureI.(*dataset)
-				future.generate(ethash.config.DatasetDir, ethash.config.DatasetsOnDisk, ethash.config.PowMode == ModeTest)
+				future.generate(ethash.config.DatasetDir, ethash.config.DatasetsOnDisk, ethash.config.DatasetsLockMmap, ethash.config.PowMode == ModeTest)
 			}
 		}()
 	} else {
 		// Either blocking generation was requested, or already done
-		current.generate(ethash.config.DatasetDir, ethash.config.DatasetsOnDisk, ethash.config.PowMode == ModeTest)
+		current.generate(ethash.config.DatasetDir, ethash.config.DatasetsOnDisk, ethash.config.DatasetsLockMmap, ethash.config.PowMode == ModeTest)
 
 		if futureI != nil {
 			future := futureI.(*dataset)
-			go future.generate(ethash.config.DatasetDir, ethash.config.DatasetsOnDisk, ethash.config.PowMode == ModeTest)
+			go future.generate(ethash.config.DatasetDir, ethash.config.DatasetsOnDisk, ethash.config.DatasetsLockMmap, ethash.config.PowMode == ModeTest)
 		}
 	}
 	return current

eth/backend.go

@@ -269,9 +269,11 @@ func CreateConsensusEngine(ctx *node.ServiceContext, chainConfig *params.ChainCo
 			CacheDir:         ctx.ResolvePath(config.CacheDir),
 			CachesInMem:      config.CachesInMem,
 			CachesOnDisk:     config.CachesOnDisk,
+			CachesLockMmap:   config.CachesLockMmap,
 			DatasetDir:       config.DatasetDir,
 			DatasetsInMem:    config.DatasetsInMem,
 			DatasetsOnDisk:   config.DatasetsOnDisk,
+			DatasetsLockMmap: config.DatasetsLockMmap,
 		}, notify, noverify)
 		engine.SetThreads(-1) // Disable CPU mining
 		return engine

eth/config.go

@@ -40,8 +40,10 @@ var DefaultConfig = Config{
 		CacheDir:         "ethash",
 		CachesInMem:      2,
 		CachesOnDisk:     3,
+		CachesLockMmap:   false,
 		DatasetsInMem:    1,
 		DatasetsOnDisk:   2,
+		DatasetsLockMmap: false,
 	},
 	NetworkId:          1,
 	LightPeers:         100,