syncmap: add a synchronized map implementation.
This is a draft for the sync.Map API proposed in golang/go#18177. It supports fast-path loads via an atomic variable, falling back to a Mutex for stores. In order to keep stores amortized to O(1), loads following a store follow the Mutex path until enough loads have occurred to offset the cost of a deep copy. For mostly-read loads, such as the maps in the reflect package in the standard library, this significantly reduces cache-line contention vs. a plain RWMutex with a map. goos: linux goarch: amd64 pkg: golang.org/x/sync/syncmap BenchmarkLoadMostlyHits/*syncmap_test.DeepCopyMap 20000000 73.1 ns/op BenchmarkLoadMostlyHits/*syncmap_test.DeepCopyMap-48 100000000 13.8 ns/op BenchmarkLoadMostlyHits/*syncmap_test.RWMutexMap 20000000 87.7 ns/op BenchmarkLoadMostlyHits/*syncmap_test.RWMutexMap-48 10000000 154 ns/op BenchmarkLoadMostlyHits/*syncmap.Map 20000000 72.1 ns/op BenchmarkLoadMostlyHits/*syncmap.Map-48 100000000 11.2 ns/op BenchmarkLoadMostlyMisses/*syncmap_test.DeepCopyMap 20000000 63.2 ns/op BenchmarkLoadMostlyMisses/*syncmap_test.DeepCopyMap-48 200000000 14.2 ns/op BenchmarkLoadMostlyMisses/*syncmap_test.RWMutexMap 20000000 72.7 ns/op BenchmarkLoadMostlyMisses/*syncmap_test.RWMutexMap-48 10000000 150 ns/op BenchmarkLoadMostlyMisses/*syncmap.Map 30000000 56.4 ns/op BenchmarkLoadMostlyMisses/*syncmap.Map-48 200000000 9.77 ns/op BenchmarkLoadOrStoreBalanced/*syncmap_test.RWMutexMap 2000000 683 ns/op BenchmarkLoadOrStoreBalanced/*syncmap_test.RWMutexMap-48 1000000 1394 ns/op BenchmarkLoadOrStoreBalanced/*syncmap.Map 2000000 645 ns/op BenchmarkLoadOrStoreBalanced/*syncmap.Map-48 1000000 1253 ns/op BenchmarkLoadOrStoreUnique/*syncmap_test.RWMutexMap 1000000 1015 ns/op BenchmarkLoadOrStoreUnique/*syncmap_test.RWMutexMap-48 1000000 1911 ns/op BenchmarkLoadOrStoreUnique/*syncmap.Map 1000000 1018 ns/op BenchmarkLoadOrStoreUnique/*syncmap.Map-48 1000000 1776 ns/op BenchmarkLoadOrStoreCollision/*syncmap_test.DeepCopyMap 50000000 30.2 ns/op BenchmarkLoadOrStoreCollision/*syncmap_test.DeepCopyMap-48 2000000000 1.24 ns/op BenchmarkLoadOrStoreCollision/*syncmap_test.RWMutexMap 30000000 50.1 ns/op BenchmarkLoadOrStoreCollision/*syncmap_test.RWMutexMap-48 5000000 451 ns/op BenchmarkLoadOrStoreCollision/*syncmap.Map 30000000 36.8 ns/op BenchmarkLoadOrStoreCollision/*syncmap.Map-48 2000000000 1.24 ns/op BenchmarkAdversarialAlloc/*syncmap_test.DeepCopyMap 10000000 213 ns/op BenchmarkAdversarialAlloc/*syncmap_test.DeepCopyMap-48 1000000 5012 ns/op BenchmarkAdversarialAlloc/*syncmap_test.RWMutexMap 20000000 68.8 ns/op BenchmarkAdversarialAlloc/*syncmap_test.RWMutexMap-48 5000000 429 ns/op BenchmarkAdversarialAlloc/*syncmap.Map 5000000 229 ns/op BenchmarkAdversarialAlloc/*syncmap.Map-48 2000000 600 ns/op BenchmarkAdversarialDelete/*syncmap_test.DeepCopyMap 5000000 314 ns/op BenchmarkAdversarialDelete/*syncmap_test.DeepCopyMap-48 2000000 726 ns/op BenchmarkAdversarialDelete/*syncmap_test.RWMutexMap 20000000 63.2 ns/op BenchmarkAdversarialDelete/*syncmap_test.RWMutexMap-48 5000000 469 ns/op BenchmarkAdversarialDelete/*syncmap.Map 10000000 203 ns/op BenchmarkAdversarialDelete/*syncmap.Map-48 10000000 253 ns/op goos: linux goarch: ppc64le pkg: golang.org/x/sync/syncmap BenchmarkLoadMostlyHits/*syncmap_test.DeepCopyMap 5000000 253 ns/op BenchmarkLoadMostlyHits/*syncmap_test.DeepCopyMap-48 50000000 26.2 ns/op BenchmarkLoadMostlyHits/*syncmap_test.RWMutexMap 5000000 505 ns/op BenchmarkLoadMostlyHits/*syncmap_test.RWMutexMap-48 3000000 443 ns/op BenchmarkLoadMostlyHits/*syncmap.Map 10000000 200 ns/op BenchmarkLoadMostlyHits/*syncmap.Map-48 100000000 18.1 ns/op BenchmarkLoadMostlyMisses/*syncmap_test.DeepCopyMap 10000000 162 ns/op BenchmarkLoadMostlyMisses/*syncmap_test.DeepCopyMap-48 100000000 23.8 ns/op BenchmarkLoadMostlyMisses/*syncmap_test.RWMutexMap 10000000 195 ns/op BenchmarkLoadMostlyMisses/*syncmap_test.RWMutexMap-48 3000000 531 ns/op BenchmarkLoadMostlyMisses/*syncmap.Map 10000000 182 ns/op BenchmarkLoadMostlyMisses/*syncmap.Map-48 100000000 15.8 ns/op BenchmarkLoadOrStoreBalanced/*syncmap_test.RWMutexMap 1000000 1664 ns/op BenchmarkLoadOrStoreBalanced/*syncmap_test.RWMutexMap-48 1000000 1768 ns/op BenchmarkLoadOrStoreBalanced/*syncmap.Map 1000000 2128 ns/op BenchmarkLoadOrStoreBalanced/*syncmap.Map-48 1000000 1903 ns/op BenchmarkLoadOrStoreUnique/*syncmap_test.RWMutexMap 1000000 2657 ns/op BenchmarkLoadOrStoreUnique/*syncmap_test.RWMutexMap-48 1000000 2577 ns/op BenchmarkLoadOrStoreUnique/*syncmap.Map 1000000 1714 ns/op BenchmarkLoadOrStoreUnique/*syncmap.Map-48 1000000 2484 ns/op BenchmarkLoadOrStoreCollision/*syncmap_test.DeepCopyMap 10000000 130 ns/op BenchmarkLoadOrStoreCollision/*syncmap_test.DeepCopyMap-48 100000000 11.3 ns/op BenchmarkLoadOrStoreCollision/*syncmap_test.RWMutexMap 3000000 426 ns/op BenchmarkLoadOrStoreCollision/*syncmap_test.RWMutexMap-48 2000000 930 ns/op BenchmarkLoadOrStoreCollision/*syncmap.Map 10000000 131 ns/op BenchmarkLoadOrStoreCollision/*syncmap.Map-48 300000000 4.07 ns/op BenchmarkAdversarialAlloc/*syncmap_test.DeepCopyMap 3000000 447 ns/op BenchmarkAdversarialAlloc/*syncmap_test.DeepCopyMap-48 300000 4159 ns/op BenchmarkAdversarialAlloc/*syncmap_test.RWMutexMap 10000000 191 ns/op BenchmarkAdversarialAlloc/*syncmap_test.RWMutexMap-48 3000000 535 ns/op BenchmarkAdversarialAlloc/*syncmap.Map 2000000 525 ns/op BenchmarkAdversarialAlloc/*syncmap.Map-48 1000000 1000 ns/op BenchmarkAdversarialDelete/*syncmap_test.DeepCopyMap 2000000 711 ns/op BenchmarkAdversarialDelete/*syncmap_test.DeepCopyMap-48 2000000 900 ns/op BenchmarkAdversarialDelete/*syncmap_test.RWMutexMap 3000000 354 ns/op BenchmarkAdversarialDelete/*syncmap_test.RWMutexMap-48 3000000 473 ns/op BenchmarkAdversarialDelete/*syncmap.Map 2000000 1357 ns/op BenchmarkAdversarialDelete/*syncmap.Map-48 5000000 334 ns/op Updates golang/go#18177 Change-Id: I8d561b617b1cd2ca03a8e68a5d5a28a519a0ce38 Reviewed-on: https://go-review.googlesource.com/33912 Reviewed-by: Russ Cox <rsc@golang.org>
This commit is contained in:
Bryan C. Mills
Bryan Mills
parent
450f422ab2
commit
54b13b0b03
4 changed files with 649 additions and 0 deletions
116
syncmap/map_test.go
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116
syncmap/map_test.go
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// Copyright 2016 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package syncmap_test
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import (
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"fmt"
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"math/rand"
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"reflect"
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"testing"
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"testing/quick"
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"golang.org/x/sync/syncmap"
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)
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// mapCall is a quick.Generator for calls on mapInterface.
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type mapCall struct {
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key interface{}
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apply func(mapInterface) (interface{}, bool)
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desc string
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}
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type mapResult struct {
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value interface{}
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ok bool
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}
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var stringType = reflect.TypeOf("")
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func randValue(r *rand.Rand) interface{} {
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k, ok := quick.Value(stringType, r)
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if !ok {
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panic(fmt.Sprintf("quick.Value(%v, _) failed", stringType))
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}
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return k.Interface()
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}
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func (mapCall) Generate(r *rand.Rand, size int) reflect.Value {
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k := randValue(r)
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var (
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app func(mapInterface) (interface{}, bool)
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desc string
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)
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switch rand.Intn(4) {
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case 0:
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app = func(m mapInterface) (interface{}, bool) {
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return m.Load(k)
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}
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desc = fmt.Sprintf("Load(%q)", k)
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case 1:
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v := randValue(r)
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app = func(m mapInterface) (interface{}, bool) {
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m.Store(k, v)
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return nil, false
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}
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desc = fmt.Sprintf("Store(%q, %q)", k, v)
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case 2:
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v := randValue(r)
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app = func(m mapInterface) (interface{}, bool) {
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return m.LoadOrStore(k, v)
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}
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desc = fmt.Sprintf("LoadOrStore(%q, %q)", k, v)
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case 3:
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app = func(m mapInterface) (interface{}, bool) {
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m.Delete(k)
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return nil, false
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}
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desc = fmt.Sprintf("Delete(%q)", k)
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}
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return reflect.ValueOf(mapCall{k, app, desc})
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}
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func applyCalls(m mapInterface, calls []mapCall) (results []mapResult, final map[interface{}]interface{}) {
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for _, c := range calls {
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v, ok := c.apply(m)
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results = append(results, mapResult{v, ok})
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}
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final = make(map[interface{}]interface{})
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m.Range(func(k, v interface{}) bool {
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final[k] = v
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return true
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})
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return results, final
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}
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func applyMap(calls []mapCall) ([]mapResult, map[interface{}]interface{}) {
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return applyCalls(new(syncmap.Map), calls)
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}
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func applyRWMutexMap(calls []mapCall) ([]mapResult, map[interface{}]interface{}) {
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return applyCalls(new(RWMutexMap), calls)
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}
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func applyDeepCopyMap(calls []mapCall) ([]mapResult, map[interface{}]interface{}) {
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return applyCalls(new(DeepCopyMap), calls)
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}
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func TestMapMatchesRWMutex(t *testing.T) {
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if err := quick.CheckEqual(applyMap, applyRWMutexMap, nil); err != nil {
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t.Error(err)
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}
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}
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func TestMapMatchesDeepCopy(t *testing.T) {
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if err := quick.CheckEqual(applyMap, applyRWMutexMap, nil); err != nil {
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t.Error(err)
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}
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}
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