76 lines
1.6 KiB
Go
76 lines
1.6 KiB
Go
package shardedmutex
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import (
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"hash/maphash"
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"sync"
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)
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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
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// name old time/op new time/op delta
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// Locks-8 74.6ns ± 7% 12.3ns ± 2% -83.54% (p=0.000 n=20+18)
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type paddedMutex struct {
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mt sync.Mutex
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pad [cacheline - 8]uint8
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}
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type ShardedMutex struct {
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shards []paddedMutex
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}
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// New creates a new ShardedMutex with N shards
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func New(nShards int) ShardedMutex {
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if nShards < 1 {
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panic("n_shards cannot be less than 1")
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}
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return ShardedMutex{
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shards: make([]paddedMutex, nShards),
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}
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}
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func (sm ShardedMutex) Shards() int {
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return len(sm.shards)
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}
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func (sm ShardedMutex) Lock(shard int) {
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sm.shards[shard].mt.Lock()
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}
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func (sm ShardedMutex) Unlock(shard int) {
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sm.shards[shard].mt.Unlock()
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}
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func (sm ShardedMutex) GetLock(shard int) sync.Locker {
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return &sm.shards[shard].mt
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}
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type ShardedMutexFor[K any] struct {
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inner ShardedMutex
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hasher func(maphash.Seed, K) uint64
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seed maphash.Seed
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}
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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]{
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inner: New(nShards),
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hasher: hasher,
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seed: maphash.MakeSeed(),
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}
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}
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func (sm ShardedMutexFor[K]) shardFor(key K) int {
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return int(sm.hasher(sm.seed, key) % uint64(len(sm.inner.shards)))
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}
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func (sm ShardedMutexFor[K]) Lock(key K) {
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sm.inner.Lock(sm.shardFor(key))
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}
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func (sm ShardedMutexFor[K]) Unlock(key K) {
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sm.inner.Unlock(sm.shardFor(key))
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}
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func (sm ShardedMutexFor[K]) GetLock(key K) sync.Locker {
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return sm.inner.GetLock(sm.shardFor(key))
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}
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