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consensus/ethash: improve cache/dataset handling (#15864)

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* consensus/ethash: add maxEpoch constant

* consensus/ethash: improve cache/dataset handling

There are two fixes in this commit:

Unmap the memory through a finalizer like the libethash wrapper did. The
release logic was incorrect and freed the memory while it was being
used, leading to crashes like in #14495 or #14943.

Track caches and datasets using simplelru instead of reinventing LRU
logic. This should make it easier to see whether it's correct.

* consensus/ethash: restore 'future item' logic in lru

* consensus/ethash: use mmap even in test mode

This makes it possible to shorten the time taken for TestCacheFileEvict.

* consensus/ethash: shuffle func calc*Size comments around

* consensus/ethash: ensure future cache/dataset is in the lru cache

* consensus/ethash: add issue link to the new test

* consensus/ethash: fix vet

* consensus/ethash: fix test

* consensus: tiny issue + nitpick fixes
This commit is contained in:
Felix Lange
2018-01-23 11:05:30 +01:00
committed by Péter Szilágyi
parent 5d4267911a
commit 924065e19d
8 changed files with 208 additions and 213 deletions
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288
consensus/ethash/ethash.go
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@ -26,6 +26,7 @@ import (
"os"
"path/filepath"
"reflect"
"runtime"
"strconv"
"sync"
"time"
@ -35,6 +36,7 @@ import (
"github.com/ethereum/go-ethereum/consensus"
"github.com/ethereum/go-ethereum/log"
"github.com/ethereum/go-ethereum/rpc"
"github.com/hashicorp/golang-lru/simplelru"
metrics "github.com/rcrowley/go-metrics"
)
@ -142,32 +144,82 @@ func memoryMapAndGenerate(path string, size uint64, generator func(buffer []uint
return memoryMap(path)
}
// lru tracks caches or datasets by their last use time, keeping at most N of them.
type lru struct {
what string
new func(epoch uint64) interface{}
mu sync.Mutex
// Items are kept in a LRU cache, but there is a special case:
// We always keep an item for (highest seen epoch) + 1 as the 'future item'.
cache *simplelru.LRU
future uint64
futureItem interface{}
}
// newlru create a new least-recently-used cache for ither the verification caches
// or the mining datasets.
func newlru(what string, maxItems int, new func(epoch uint64) interface{}) *lru {
if maxItems <= 0 {
maxItems = 1
}
cache, _ := simplelru.NewLRU(maxItems, func(key, value interface{}) {
log.Trace("Evicted ethash "+what, "epoch", key)
})
return &lru{what: what, new: new, cache: cache}
}
// get retrieves or creates an item for the given epoch. The first return value is always
// non-nil. The second return value is non-nil if lru thinks that an item will be useful in
// the near future.
func (lru *lru) get(epoch uint64) (item, future interface{}) {
lru.mu.Lock()
defer lru.mu.Unlock()
// Get or create the item for the requested epoch.
item, ok := lru.cache.Get(epoch)
if !ok {
if lru.future > 0 && lru.future == epoch {
item = lru.futureItem
} else {
log.Trace("Requiring new ethash "+lru.what, "epoch", epoch)
item = lru.new(epoch)
}
lru.cache.Add(epoch, item)
}
// Update the 'future item' if epoch is larger than previously seen.
if epoch < maxEpoch-1 && lru.future < epoch+1 {
log.Trace("Requiring new future ethash "+lru.what, "epoch", epoch+1)
future = lru.new(epoch + 1)
lru.future = epoch + 1
lru.futureItem = future
}
return item, future
}
// cache wraps an ethash cache with some metadata to allow easier concurrent use.
type cache struct {
epoch uint64 // Epoch for which this cache is relevant
epoch uint64 // Epoch for which this cache is relevant
dump *os.File // File descriptor of the memory mapped cache
mmap mmap.MMap // Memory map itself to unmap before releasing
cache []uint32 // The actual cache data content (may be memory mapped)
once sync.Once // Ensures the cache is generated only once
}
dump *os.File // File descriptor of the memory mapped cache
mmap mmap.MMap // Memory map itself to unmap before releasing
cache []uint32 // The actual cache data content (may be memory mapped)
used time.Time // Timestamp of the last use for smarter eviction
once sync.Once // Ensures the cache is generated only once
lock sync.Mutex // Ensures thread safety for updating the usage time
// newCache creates a new ethash verification cache and returns it as a plain Go
// interface to be usable in an LRU cache.
func newCache(epoch uint64) interface{} {
return &cache{epoch: epoch}
}
// generate ensures that the cache content is generated before use.
func (c *cache) generate(dir string, limit int, test bool) {
c.once.Do(func() {
// If we have a testing cache, generate and return
if test {
c.cache = make([]uint32, 1024/4)
generateCache(c.cache, c.epoch, seedHash(c.epoch*epochLength+1))
return
}
// If we don't store anything on disk, generate and return
size := cacheSize(c.epoch*epochLength + 1)
seed := seedHash(c.epoch*epochLength + 1)
if test {
size = 1024
}
// If we don't store anything on disk, generate and return.
if dir == "" {
c.cache = make([]uint32, size/4)
generateCache(c.cache, c.epoch, seed)
@ -181,6 +233,10 @@ func (c *cache) generate(dir string, limit int, test bool) {
path := filepath.Join(dir, fmt.Sprintf("cache-R%d-%x%s", algorithmRevision, seed[:8], endian))
logger := log.New("epoch", c.epoch)
// We're about to mmap the file, ensure that the mapping is cleaned up when the
// cache becomes unused.
runtime.SetFinalizer(c, (*cache).finalizer)
// Try to load the file from disk and memory map it
var err error
c.dump, c.mmap, c.cache, err = memoryMap(path)
@ -207,49 +263,41 @@ func (c *cache) generate(dir string, limit int, test bool) {
})
}
// release closes any file handlers and memory maps open.
func (c *cache) release() {
// finalizer unmaps the memory and closes the file.
func (c *cache) finalizer() {
if c.mmap != nil {
c.mmap.Unmap()
c.mmap = nil
}
if c.dump != nil {
c.dump.Close()
c.dump = nil
c.mmap, c.dump = nil, nil
}
}
// dataset wraps an ethash dataset with some metadata to allow easier concurrent use.
type dataset struct {
epoch uint64 // Epoch for which this cache is relevant
epoch uint64 // Epoch for which this cache is relevant
dump *os.File // File descriptor of the memory mapped cache
mmap mmap.MMap // Memory map itself to unmap before releasing
dataset []uint32 // The actual cache data content
once sync.Once // Ensures the cache is generated only once
}
dump *os.File // File descriptor of the memory mapped cache
mmap mmap.MMap // Memory map itself to unmap before releasing
dataset []uint32 // The actual cache data content
used time.Time // Timestamp of the last use for smarter eviction
once sync.Once // Ensures the cache is generated only once
lock sync.Mutex // Ensures thread safety for updating the usage time
// newDataset creates a new ethash mining dataset and returns it as a plain Go
// interface to be usable in an LRU cache.
func newDataset(epoch uint64) interface{} {
return &dataset{epoch: epoch}
}
// generate ensures that the dataset content is generated before use.
func (d *dataset) generate(dir string, limit int, test bool) {
d.once.Do(func() {
// If we have a testing dataset, generate and return
if test {
cache := make([]uint32, 1024/4)
generateCache(cache, d.epoch, seedHash(d.epoch*epochLength+1))
d.dataset = make([]uint32, 32*1024/4)
generateDataset(d.dataset, d.epoch, cache)
return
}
// If we don't store anything on disk, generate and return
csize := cacheSize(d.epoch*epochLength + 1)
dsize := datasetSize(d.epoch*epochLength + 1)
seed := seedHash(d.epoch*epochLength + 1)
if test {
csize = 1024
dsize = 32 * 1024
}
// If we don't store anything on disk, generate and return
if dir == "" {
cache := make([]uint32, csize/4)
generateCache(cache, d.epoch, seed)
@ -265,6 +313,10 @@ func (d *dataset) generate(dir string, limit int, test bool) {
path := filepath.Join(dir, fmt.Sprintf("full-R%d-%x%s", algorithmRevision, seed[:8], endian))
logger := log.New("epoch", d.epoch)
// We're about to mmap the file, ensure that the mapping is cleaned up when the
// cache becomes unused.
runtime.SetFinalizer(d, (*dataset).finalizer)
// Try to load the file from disk and memory map it
var err error
d.dump, d.mmap, d.dataset, err = memoryMap(path)
@ -294,15 +346,12 @@ func (d *dataset) generate(dir string, limit int, test bool) {
})
}
// release closes any file handlers and memory maps open.
func (d *dataset) release() {
// finalizer closes any file handlers and memory maps open.
func (d *dataset) finalizer() {
if d.mmap != nil {
d.mmap.Unmap()
d.mmap = nil
}
if d.dump != nil {
d.dump.Close()
d.dump = nil
d.mmap, d.dump = nil, nil
}
}
@ -310,14 +359,12 @@ func (d *dataset) release() {
func MakeCache(block uint64, dir string) {
c := cache{epoch: block / epochLength}
c.generate(dir, math.MaxInt32, false)
c.release()
}
// 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.release()
}
// Mode defines the type and amount of PoW verification an ethash engine makes.
@ -347,10 +394,8 @@ type Config struct {
type Ethash struct {
config Config
caches map[uint64]*cache // In memory caches to avoid regenerating too often
fcache *cache // Pre-generated cache for the estimated future epoch
datasets map[uint64]*dataset // In memory datasets to avoid regenerating too often
fdataset *dataset // Pre-generated dataset for the estimated future epoch
caches *lru // In memory caches to avoid regenerating too often
datasets *lru // In memory datasets to avoid regenerating too often
// Mining related fields
rand *rand.Rand // Properly seeded random source for nonces
@ -380,8 +425,8 @@ func New(config Config) *Ethash {
}
return &Ethash{
config: config,
caches: make(map[uint64]*cache),
datasets: make(map[uint64]*dataset),
caches: newlru("cache", config.CachesInMem, newCache),
datasets: newlru("dataset", config.DatasetsInMem, newDataset),
update: make(chan struct{}),
hashrate: metrics.NewMeter(),
}
@ -390,16 +435,7 @@ func New(config Config) *Ethash {
// NewTester creates a small sized ethash PoW scheme useful only for testing
// purposes.
func NewTester() *Ethash {
return &Ethash{
config: Config{
CachesInMem: 1,
PowMode: ModeTest,
},
caches: make(map[uint64]*cache),
datasets: make(map[uint64]*dataset),
update: make(chan struct{}),
hashrate: metrics.NewMeter(),
}
return New(Config{CachesInMem: 1, PowMode: ModeTest})
}
// NewFaker creates a ethash consensus engine with a fake PoW scheme that accepts
@ -456,126 +492,40 @@ func NewShared() *Ethash {
// cache tries to retrieve a verification cache for the specified block number
// by first checking against a list of in-memory caches, then against caches
// stored on disk, and finally generating one if none can be found.
func (ethash *Ethash) cache(block uint64) []uint32 {
func (ethash *Ethash) cache(block uint64) *cache {
epoch := block / epochLength
currentI, futureI := ethash.caches.get(epoch)
current := currentI.(*cache)
// If we have a PoW for that epoch, use that
ethash.lock.Lock()
current, future := ethash.caches[epoch], (*cache)(nil)
if current == nil {
// No in-memory cache, evict the oldest if the cache limit was reached
for len(ethash.caches) > 0 && len(ethash.caches) >= ethash.config.CachesInMem {
var evict *cache
for _, cache := range ethash.caches {
if evict == nil || evict.used.After(cache.used) {
evict = cache
}
}
delete(ethash.caches, evict.epoch)
evict.release()
log.Trace("Evicted ethash cache", "epoch", evict.epoch, "used", evict.used)
}
// If we have the new cache pre-generated, use that, otherwise create a new one
if ethash.fcache != nil && ethash.fcache.epoch == epoch {
log.Trace("Using pre-generated cache", "epoch", epoch)
current, ethash.fcache = ethash.fcache, nil
} else {
log.Trace("Requiring new ethash cache", "epoch", epoch)
current = &cache{epoch: epoch}
}
ethash.caches[epoch] = current
// If we just used up the future cache, or need a refresh, regenerate
if ethash.fcache == nil || ethash.fcache.epoch <= epoch {
if ethash.fcache != nil {
ethash.fcache.release()
}
log.Trace("Requiring new future ethash cache", "epoch", epoch+1)
future = &cache{epoch: epoch + 1}
ethash.fcache = future
}
// New current cache, set its initial timestamp
current.used = time.Now()
}
ethash.lock.Unlock()
// Wait for generation finish, bump the timestamp and finalize the cache
// Wait for generation finish.
current.generate(ethash.config.CacheDir, ethash.config.CachesOnDisk, ethash.config.PowMode == ModeTest)
current.lock.Lock()
current.used = time.Now()
current.lock.Unlock()
// If we exhausted the future cache, now's a good time to regenerate it
if future != nil {
// 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)
}
return current.cache
return current
}
// dataset tries to retrieve a mining dataset for the specified block number
// by first checking against a list of in-memory datasets, then against DAGs
// stored on disk, and finally generating one if none can be found.
func (ethash *Ethash) dataset(block uint64) []uint32 {
func (ethash *Ethash) dataset(block uint64) *dataset {
epoch := block / epochLength
currentI, futureI := ethash.datasets.get(epoch)
current := currentI.(*dataset)
// If we have a PoW for that epoch, use that
ethash.lock.Lock()
current, future := ethash.datasets[epoch], (*dataset)(nil)
if current == nil {
// No in-memory dataset, evict the oldest if the dataset limit was reached
for len(ethash.datasets) > 0 && len(ethash.datasets) >= ethash.config.DatasetsInMem {
var evict *dataset
for _, dataset := range ethash.datasets {
if evict == nil || evict.used.After(dataset.used) {
evict = dataset
}
}
delete(ethash.datasets, evict.epoch)
evict.release()
log.Trace("Evicted ethash dataset", "epoch", evict.epoch, "used", evict.used)
}
// If we have the new cache pre-generated, use that, otherwise create a new one
if ethash.fdataset != nil && ethash.fdataset.epoch == epoch {
log.Trace("Using pre-generated dataset", "epoch", epoch)
current = &dataset{epoch: ethash.fdataset.epoch} // Reload from disk
ethash.fdataset = nil
} else {
log.Trace("Requiring new ethash dataset", "epoch", epoch)
current = &dataset{epoch: epoch}
}
ethash.datasets[epoch] = current
// If we just used up the future dataset, or need a refresh, regenerate
if ethash.fdataset == nil || ethash.fdataset.epoch <= epoch {
if ethash.fdataset != nil {
ethash.fdataset.release()
}
log.Trace("Requiring new future ethash dataset", "epoch", epoch+1)
future = &dataset{epoch: epoch + 1}
ethash.fdataset = future
}
// New current dataset, set its initial timestamp
current.used = time.Now()
}
ethash.lock.Unlock()
// Wait for generation finish, bump the timestamp and finalize the cache
// Wait for generation finish.
current.generate(ethash.config.DatasetDir, ethash.config.DatasetsOnDisk, ethash.config.PowMode == ModeTest)
current.lock.Lock()
current.used = time.Now()
current.lock.Unlock()
// If we exhausted the future dataset, now's a good time to regenerate it
if future != nil {
// If we need a new future dataset, now's a good time to regenerate it.
if futureI != nil {
future := futureI.(*dataset)
go future.generate(ethash.config.DatasetDir, ethash.config.DatasetsOnDisk, ethash.config.PowMode == ModeTest)
}
return current.dataset
return current
}
// Threads returns the number of mining threads currently enabled. This doesn't