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6970f725c9
An extra sync.Pool was added during a refactor which caused some 64 bit, atomically accessed variables to no longer be 64 bit aligned. By moving all atomically accessed variables to the beginning of the struct they are guaranteed to be 64 bit aligned. Signed-off-by: Chris Marchbanks <csmarchbanks@gmail.com>
104 lines
2.2 KiB
Go
104 lines
2.2 KiB
Go
// Copyright 2019 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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// Inspired / copied / modified from https://gitlab.com/cznic/strutil/blob/master/strutil.go,
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// which is MIT licensed, so:
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//
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// Copyright (c) 2014 The strutil Authors. All rights reserved.
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package remote
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import (
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"sync"
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"sync/atomic"
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"github.com/prometheus/client_golang/prometheus"
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"github.com/prometheus/client_golang/prometheus/promauto"
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)
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var interner = newPool()
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var noReferenceReleases = promauto.NewCounter(prometheus.CounterOpts{
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Namespace: namespace,
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Subsystem: subsystem,
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Name: "string_interner_zero_reference_releases_total",
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Help: "The number of times release has been called for strings that are not interned.",
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})
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type pool struct {
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mtx sync.RWMutex
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pool map[string]*entry
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}
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type entry struct {
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// Keep all 64bit atomically accessed variables at the top of this struct.
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// See https://golang.org/pkg/sync/atomic/#pkg-note-BUG for more info.
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refs int64
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s string
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}
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func newPool() *pool {
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return &pool{
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pool: map[string]*entry{},
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}
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}
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func (p *pool) intern(s string) string {
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if s == "" {
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return ""
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}
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p.mtx.RLock()
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interned, ok := p.pool[s]
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p.mtx.RUnlock()
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if ok {
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atomic.AddInt64(&interned.refs, 1)
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return interned.s
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}
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p.mtx.Lock()
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defer p.mtx.Unlock()
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if interned, ok := p.pool[s]; ok {
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atomic.AddInt64(&interned.refs, 1)
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return interned.s
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}
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p.pool[s] = &entry{
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s: s,
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refs: 1,
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}
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return s
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}
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func (p *pool) release(s string) {
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p.mtx.RLock()
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interned, ok := p.pool[s]
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p.mtx.RUnlock()
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if !ok {
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noReferenceReleases.Inc()
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return
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}
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refs := atomic.AddInt64(&interned.refs, -1)
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if refs > 0 {
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return
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}
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p.mtx.Lock()
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defer p.mtx.Unlock()
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if atomic.LoadInt64(&interned.refs) != 0 {
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return
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}
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delete(p.pool, s)
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}
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