feat: chainstore: sharded mutex for filling chain height index #10934
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,75 @@ | ||
| package shardedmutex | ||
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| import ( | ||
| "hash/maphash" | ||
| "sync" | ||
| ) | ||
|
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| const cacheline = 64 | ||
|
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| // padding a mutex to a cacheline improves performance as the cachelines are not contested | ||
| // name old time/op new time/op delta | ||
| // Locks-8 74.6ns ± 7% 12.3ns ± 2% -83.54% (p=0.000 n=20+18) | ||
| type paddedMutex struct { | ||
| mt sync.Mutex | ||
| pad [cacheline - 8]uint8 | ||
| } | ||
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| type ShardedMutex struct { | ||
| shards []paddedMutex | ||
| } | ||
|
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| // New creates a new ShardedMutex with N shards | ||
| func New(nShards int) ShardedMutex { | ||
| if nShards < 1 { | ||
| panic("n_shards cannot be less than 1") | ||
| } | ||
| return ShardedMutex{ | ||
| shards: make([]paddedMutex, nShards), | ||
| } | ||
| } | ||
|
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| func (sm ShardedMutex) Shards() int { | ||
| return len(sm.shards) | ||
| } | ||
|
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| func (sm ShardedMutex) Lock(shard int) { | ||
| sm.shards[shard].mt.Lock() | ||
| } | ||
|
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| func (sm ShardedMutex) Unlock(shard int) { | ||
| sm.shards[shard].mt.Unlock() | ||
| } | ||
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| func (sm ShardedMutex) GetLock(shard int) sync.Locker { | ||
| return &sm.shards[shard].mt | ||
| } | ||
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| type ShardedMutexFor[K any] struct { | ||
| inner ShardedMutex | ||
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| hasher func(maphash.Seed, K) uint64 | ||
| seed maphash.Seed | ||
| } | ||
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| func NewFor[K any](hasher func(maphash.Seed, K) uint64, nShards int) ShardedMutexFor[K] { | ||
|
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| return ShardedMutexFor[K]{ | ||
| inner: New(nShards), | ||
| hasher: hasher, | ||
| seed: maphash.MakeSeed(), | ||
| } | ||
| } | ||
|
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| func (sm ShardedMutexFor[K]) shardFor(key K) int { | ||
| return int(sm.hasher(sm.seed, key) % uint64(len(sm.inner.shards))) | ||
| } | ||
|
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| func (sm ShardedMutexFor[K]) Lock(key K) { | ||
| sm.inner.Lock(sm.shardFor(key)) | ||
| } | ||
| func (sm ShardedMutexFor[K]) Unlock(key K) { | ||
| sm.inner.Unlock(sm.shardFor(key)) | ||
| } | ||
| func (sm ShardedMutexFor[K]) GetLock(key K) sync.Locker { | ||
| return sm.inner.GetLock(sm.shardFor(key)) | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,159 @@ | ||
| package shardedmutex | ||
|
|
||
| import ( | ||
| "fmt" | ||
| "hash/maphash" | ||
| "runtime" | ||
| "sync" | ||
| "sync/atomic" | ||
| "testing" | ||
| "time" | ||
| ) | ||
|
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| func TestLockingDifferentShardsDoesNotBlock(t *testing.T) { | ||
| shards := 16 | ||
| sm := New(shards) | ||
| done := make(chan struct{}) | ||
| go func() { | ||
| select { | ||
| case <-done: | ||
| return | ||
| case <-time.After(5 * time.Second): | ||
| panic("test locked up") | ||
| } | ||
| }() | ||
| for i := 0; i < shards; i++ { | ||
| sm.Lock(i) | ||
| } | ||
|
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| close(done) | ||
| } | ||
| func TestLockingSameShardsBlocks(t *testing.T) { | ||
| shards := 16 | ||
| sm := New(shards) | ||
| wg := sync.WaitGroup{} | ||
| wg.Add(shards) | ||
| ch := make(chan int, shards) | ||
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| for i := 0; i < shards; i++ { | ||
| go func(i int) { | ||
| if i != 15 { | ||
| sm.Lock(i) | ||
| } | ||
| wg.Done() | ||
| wg.Wait() | ||
| sm.Lock((15 + i) % shards) | ||
| ch <- i | ||
| sm.Unlock(i) | ||
| }(i) | ||
| } | ||
|
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| wg.Wait() | ||
| for i := 0; i < 2*shards; i++ { | ||
| runtime.Gosched() | ||
| } | ||
| for i := 0; i < shards; i++ { | ||
| if a := <-ch; a != i { | ||
| t.Errorf("got %d instead of %d", a, i) | ||
| } | ||
| } | ||
| } | ||
|
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| func TestShardedByString(t *testing.T) { | ||
| shards := 16 | ||
| sm := NewFor(maphash.String, shards) | ||
|
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| wg1 := sync.WaitGroup{} | ||
| wg1.Add(shards * 20) | ||
| wg2 := sync.WaitGroup{} | ||
| wg2.Add(shards * 20) | ||
|
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| active := atomic.Int32{} | ||
| max := atomic.Int32{} | ||
|
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| for i := 0; i < shards*20; i++ { | ||
| go func(i int) { | ||
| wg1.Done() | ||
| wg1.Wait() | ||
| sm.Lock(fmt.Sprintf("goroutine %d", i)) | ||
| activeNew := active.Add(1) | ||
| for { | ||
| curMax := max.Load() | ||
| if curMax >= activeNew { | ||
| break | ||
| } | ||
| if max.CompareAndSwap(curMax, activeNew) { | ||
| break | ||
| } | ||
| } | ||
| for j := 0; j < 100; j++ { | ||
| runtime.Gosched() | ||
| } | ||
| active.Add(-1) | ||
| sm.Unlock(fmt.Sprintf("goroutine %d", i)) | ||
| wg2.Done() | ||
| }(i) | ||
| } | ||
|
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| wg2.Wait() | ||
|
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| if max.Load() != 16 { | ||
| t.Fatal("max load not achieved", max.Load()) | ||
| } | ||
|
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| } | ||
|
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| func BenchmarkShardedMutex(b *testing.B) { | ||
| shards := 16 | ||
| sm := New(shards) | ||
|
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| done := atomic.Int32{} | ||
| go func() { | ||
| for { | ||
| sm.Lock(0) | ||
| sm.Unlock(0) | ||
| if done.Load() != 0 { | ||
| return | ||
| } | ||
| } | ||
| }() | ||
| for i := 0; i < 100; i++ { | ||
| runtime.Gosched() | ||
| } | ||
|
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| b.ResetTimer() | ||
| for i := 0; i < b.N; i++ { | ||
| sm.Lock(1) | ||
| sm.Unlock(1) | ||
| } | ||
| done.Add(1) | ||
| } | ||
|
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| func BenchmarkShardedMutexOf(b *testing.B) { | ||
| shards := 16 | ||
| sm := NewFor(maphash.String, shards) | ||
|
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| str1 := "string1" | ||
| str2 := "string2" | ||
|
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| done := atomic.Int32{} | ||
| go func() { | ||
| for { | ||
| sm.Lock(str1) | ||
| sm.Unlock(str1) | ||
| if done.Load() != 0 { | ||
| return | ||
| } | ||
| } | ||
| }() | ||
| for i := 0; i < 100; i++ { | ||
| runtime.Gosched() | ||
| } | ||
|
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| b.ResetTimer() | ||
| for i := 0; i < b.N; i++ { | ||
| sm.Lock(str2) | ||
| sm.Unlock(str2) | ||
| } | ||
| done.Add(1) | ||
| } |
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Could you write a little more about when this can be used?