93 lines
2.4 KiB
Go
93 lines
2.4 KiB
Go
// Package sync is an extension of the stdlib "sync" package. It has extra
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// functionality that helps debug the use of synchronization primitives. The
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// package should be importable in place of "sync". The extra functionality
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// can be enabled by calling Enable() or passing a non-empty PPROF_SYNC
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// environment variable to the process.
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//
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// Several profiles are exposed on the default HTTP muxer (and to
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// "/debug/pprof" when "net/http/pprof" is imported by the process).
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// "lockHolders" lists the stack traces of goroutines that called Mutex.Lock
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// that haven't subsequently been Unlocked. "lockBlockers" contains goroutines
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// that are waiting to obtain locks. "/debug/lockTimes" or PrintLockTimes()
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// shows the longest time a lock is held for each stack trace.
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//
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// Note that currently RWMutex is treated like a Mutex when the package is
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// enabled.
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package sync
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import (
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"fmt"
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"io"
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"net/http"
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"os"
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"runtime/pprof"
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"strings"
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"sync"
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"text/tabwriter"
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"github.com/anacrolix/missinggo"
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)
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var (
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// Protects initialization and enabling of the package.
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enableMu sync.Mutex
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// Whether shared locks must be handled as exclusive locks.
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noSharedLocking = false
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contentionOn = false
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lockTimesOn = false
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// Current lock holders.
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lockHolders *pprof.Profile
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// Those blocked on acquiring a lock.
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lockBlockers *pprof.Profile
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)
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// Writes out the longest time a Mutex remains locked for each stack trace
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// that locks a Mutex.
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func PrintLockTimes(w io.Writer) {
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lockTimes := sortedLockTimes()
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tw := tabwriter.NewWriter(w, 1, 8, 1, '\t', 0)
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defer tw.Flush()
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w = tw
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for _, elem := range lockTimes {
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fmt.Fprintf(w, "%s (%s * %d [%s, %s])\n", elem.Total, elem.MeanTime(), elem.Count, elem.Min, elem.Max)
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missinggo.WriteStack(w, elem.stack[:])
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}
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}
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func Enable() {
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EnableContention()
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EnableLockTimes()
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}
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func EnableContention() {
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lockHolders = pprof.NewProfile("lockHolders")
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lockBlockers = pprof.NewProfile("lockBlockers")
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noSharedLocking = true
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contentionOn = true
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}
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func EnableLockTimes() {
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lockStatsByStack = make(map[lockStackKey]lockStats)
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http.DefaultServeMux.HandleFunc("/debug/lockTimes", func(w http.ResponseWriter, r *http.Request) {
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PrintLockTimes(w)
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})
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noSharedLocking = true
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lockTimesOn = true
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}
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func init() {
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env := os.Getenv("PPROF_SYNC")
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all := true
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if strings.Contains(env, "times") {
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EnableLockTimes()
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all = false
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}
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if strings.Contains(env, "contention") {
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EnableContention()
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all = false
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}
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if all && env != "" {
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Enable()
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}
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}
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