mirror of
https://github.com/VictoriaMetrics/VictoriaMetrics.git
synced 2024-11-23 20:37:12 +01:00
85 lines
2.7 KiB
Go
85 lines
2.7 KiB
Go
package bytesutil
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import (
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"flag"
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"strings"
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"sync"
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"sync/atomic"
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"time"
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"github.com/VictoriaMetrics/VictoriaMetrics/lib/fasttime"
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)
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var (
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internStringMaxLen = flag.Int("internStringMaxLen", 500, "The maximum length for strings to intern. A lower limit may save memory at the cost of higher CPU usage. "+
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"See https://en.wikipedia.org/wiki/String_interning . See also -internStringDisableCache and -internStringCacheExpireDuration")
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disableCache = flag.Bool("internStringDisableCache", false, "Whether to disable caches for interned strings. This may reduce memory usage at the cost of higher CPU usage. "+
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"See https://en.wikipedia.org/wiki/String_interning . See also -internStringCacheExpireDuration and -internStringMaxLen")
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cacheExpireDuration = flag.Duration("internStringCacheExpireDuration", 6*time.Minute, "The expiry duration for caches for interned strings. "+
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"See https://en.wikipedia.org/wiki/String_interning . See also -internStringMaxLen and -internStringDisableCache")
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)
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func isSkipCache(s string) bool {
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return *disableCache || len(s) > *internStringMaxLen
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}
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// InternBytes interns b as a string
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func InternBytes(b []byte) string {
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s := ToUnsafeString(b)
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return InternString(s)
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}
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// InternString returns interned s.
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//
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// This may be needed for reducing the amounts of allocated memory.
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func InternString(s string) string {
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if isSkipCache(s) {
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// Make a new copy for s in order to remove references from possible bigger string s refers to.
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// This also protects from cases when s points to unsafe string - see https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3227
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return strings.Clone(s)
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}
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ct := fasttime.UnixTimestamp()
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if v, ok := internStringsMap.Load(s); ok {
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e := v.(*ismEntry)
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if e.lastAccessTime.Load()+10 < ct {
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// Reduce the frequency of e.lastAccessTime update to once per 10 seconds
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// in order to improve the fast path speed on systems with many CPU cores.
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e.lastAccessTime.Store(ct)
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}
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return e.s
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}
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// Make a new copy for s in order to remove references from possible bigger string s refers to.
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sCopy := strings.Clone(s)
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e := &ismEntry{
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s: sCopy,
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}
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e.lastAccessTime.Store(ct)
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internStringsMap.Store(sCopy, e)
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if needCleanup(&internStringsMapLastCleanupTime, ct) {
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// Perform a global cleanup for internStringsMap by removing items, which weren't accessed during the last 5 minutes.
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m := &internStringsMap
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deadline := ct - uint64(cacheExpireDuration.Seconds())
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m.Range(func(k, v interface{}) bool {
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e := v.(*ismEntry)
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if e.lastAccessTime.Load() < deadline {
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m.Delete(k)
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}
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return true
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})
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}
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return sCopy
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}
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type ismEntry struct {
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lastAccessTime atomic.Uint64
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s string
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}
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var (
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internStringsMap sync.Map
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internStringsMapLastCleanupTime atomic.Uint64
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)
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