From: Michael Anthony Knyszek Date: Thu, 11 May 2023 21:09:10 +0000 (+0000) Subject: runtime: emit STW events for all pauses, not just those for the GC X-Git-Tag: go1.21rc1~419 X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=b1aadd034c1feb6ac8409aca5f0efd10ef442950;p=gostls13.git runtime: emit STW events for all pauses, not just those for the GC Currently STW events are only emitted for GC STWs. There's little reason why the trace can't contain events for every STW: they're rare so don't take up much space in the trace, yet being able to see when the world was stopped is often critical to debugging certain latency issues, especially when they stem from user-level APIs. This change adds new "kinds" to the EvGCSTWStart event, renames the GCSTW events to just "STW," and lets the parser deal with unknown STW kinds for future backwards compatibility. But, this change must break trace compatibility, so it bumps the trace version to Go 1.21. This change also includes a small cleanup in the trace command, which previously checked for STW events when deciding whether user tasks overlapped with a GC. Looking at the source, I don't see a way for STW events to ever enter the stream that that code looks at, so that condition has been deleted. Change-Id: I9a5dc144092c53e92eb6950e9a5504a790ac00cf Reviewed-on: https://go-review.googlesource.com/c/go/+/494495 Reviewed-by: Michael Pratt TryBot-Result: Gopher Robot Run-TryBot: Michael Knyszek --- diff --git a/src/cmd/trace/annotations.go b/src/cmd/trace/annotations.go index 9ffce1b187..0addc240be 100644 --- a/src/cmd/trace/annotations.go +++ b/src/cmd/trace/annotations.go @@ -494,7 +494,7 @@ func (region *regionDesc) duration() time.Duration { func (task *taskDesc) overlappingGCDuration(evs []*trace.Event) (overlapping time.Duration) { for _, ev := range evs { // make sure we only consider the global GC events. - if typ := ev.Type; typ != trace.EvGCStart && typ != trace.EvGCSTWStart { + if typ := ev.Type; typ != trace.EvGCStart { continue } diff --git a/src/cmd/trace/trace.go b/src/cmd/trace/trace.go index 895129998f..618df42033 100644 --- a/src/cmd/trace/trace.go +++ b/src/cmd/trace/trace.go @@ -764,12 +764,12 @@ func generateTrace(params *traceParams, consumer traceConsumer) error { case trace.EvGCStart: ctx.emitSlice(ev, "GC") case trace.EvGCDone: - case trace.EvGCSTWStart: + case trace.EvSTWStart: if ctx.mode&modeGoroutineOriented != 0 { continue } ctx.emitSlice(ev, fmt.Sprintf("STW (%s)", ev.SArgs[0])) - case trace.EvGCSTWDone: + case trace.EvSTWDone: case trace.EvGCMarkAssistStart: // Mark assists can continue past preemptions, so truncate to the // whichever comes first. We'll synthesize another slice if diff --git a/src/internal/trace/gc.go b/src/internal/trace/gc.go index c1bc862340..3bd284e200 100644 --- a/src/internal/trace/gc.go +++ b/src/internal/trace/gc.go @@ -27,6 +27,7 @@ type UtilFlags int const ( // UtilSTW means utilization should account for STW events. + // This includes non-GC STW events, which are typically user-requested. UtilSTW UtilFlags = 1 << iota // UtilBackground means utilization should account for // background mark workers. @@ -93,11 +94,11 @@ func MutatorUtilization(events []*Event, flags UtilFlags) [][]MutatorUtil { } ps = append(ps, perP{series: series}) } - case EvGCSTWStart: + case EvSTWStart: if flags&UtilSTW != 0 { stw++ } - case EvGCSTWDone: + case EvSTWDone: if flags&UtilSTW != 0 { stw-- } diff --git a/src/internal/trace/parser.go b/src/internal/trace/parser.go index 0376e914b1..67fa60b8fb 100644 --- a/src/internal/trace/parser.go +++ b/src/internal/trace/parser.go @@ -151,7 +151,7 @@ func readTrace(r io.Reader) (ver int, events []rawEvent, strings map[uint64]stri return } switch ver { - case 1005, 1007, 1008, 1009, 1010, 1011, 1019: + case 1005, 1007, 1008, 1009, 1010, 1011, 1019, 1021: // Note: When adding a new version, confirm that canned traces from the // old version are part of the test suite. Add them using mkcanned.bash. break @@ -420,18 +420,29 @@ func parseEvents(ver int, rawEvents []rawEvent, strings map[uint64]string) (even if raw.typ == EvGoStartLabel { e.SArgs = []string{strings[e.Args[2]]} } - case EvGCSTWStart: + case EvSTWStart: e.G = 0 - switch e.Args[0] { - case 0: - e.SArgs = []string{"mark termination"} - case 1: - e.SArgs = []string{"sweep termination"} - default: - err = fmt.Errorf("unknown STW kind %d", e.Args[0]) - return + if ver < 1021 { + switch e.Args[0] { + case 0: + e.SArgs = []string{"mark termination"} + case 1: + e.SArgs = []string{"sweep termination"} + default: + err = fmt.Errorf("unknown STW kind %d", e.Args[0]) + return + } + } else if ver == 1021 { + if kind := e.Args[0]; kind < uint64(len(stwReasonStringsGo121)) { + e.SArgs = []string{stwReasonStringsGo121[kind]} + } else { + e.SArgs = []string{"unknown"} + } + } else { + // Can't make any assumptions. + e.SArgs = []string{"unknown"} } - case EvGCStart, EvGCDone, EvGCSTWDone: + case EvGCStart, EvGCDone, EvSTWDone: e.G = 0 case EvGoEnd, EvGoStop, EvGoSched, EvGoPreempt, EvGoSleep, EvGoBlock, EvGoBlockSend, EvGoBlockRecv, @@ -653,20 +664,20 @@ func postProcessTrace(ver int, events []*Event) error { } evGC.Link = ev evGC = nil - case EvGCSTWStart: + case EvSTWStart: evp := &evSTW if ver < 1010 { - // Before 1.10, EvGCSTWStart was per-P. + // Before 1.10, EvSTWStart was per-P. evp = &p.evSTW } if *evp != nil { return fmt.Errorf("previous STW is not ended before a new one (offset %v, time %v)", ev.Off, ev.Ts) } *evp = ev - case EvGCSTWDone: + case EvSTWDone: evp := &evSTW if ver < 1010 { - // Before 1.10, EvGCSTWDone was per-P. + // Before 1.10, EvSTWDone was per-P. evp = &p.evSTW } if *evp == nil { @@ -1015,7 +1026,7 @@ func argNum(raw rawEvent, ver int) int { if ver < 1007 { narg-- // 1.7 added an additional seq arg } - case EvGCSTWStart: + case EvSTWStart: if ver < 1010 { narg-- // 1.10 added an argument } @@ -1038,8 +1049,8 @@ const ( EvProcStop = 6 // stop of P [timestamp] EvGCStart = 7 // GC start [timestamp, seq, stack id] EvGCDone = 8 // GC done [timestamp] - EvGCSTWStart = 9 // GC mark termination start [timestamp, kind] - EvGCSTWDone = 10 // GC mark termination done [timestamp] + EvSTWStart = 9 // GC mark termination start [timestamp, kind] + EvSTWDone = 10 // GC mark termination done [timestamp] EvGCSweepStart = 11 // GC sweep start [timestamp, stack id] EvGCSweepDone = 12 // GC sweep done [timestamp, swept, reclaimed] EvGoCreate = 13 // goroutine creation [timestamp, new goroutine id, new stack id, stack id] @@ -1098,8 +1109,8 @@ var EventDescriptions = [EvCount]struct { EvProcStop: {"ProcStop", 1005, false, []string{}, nil}, EvGCStart: {"GCStart", 1005, true, []string{"seq"}, nil}, // in 1.5 format it was {} EvGCDone: {"GCDone", 1005, false, []string{}, nil}, - EvGCSTWStart: {"GCSTWStart", 1005, false, []string{"kindid"}, []string{"kind"}}, // <= 1.9, args was {} (implicitly {0}) - EvGCSTWDone: {"GCSTWDone", 1005, false, []string{}, nil}, + EvSTWStart: {"STWStart", 1005, false, []string{"kindid"}, []string{"kind"}}, // <= 1.9, args was {} (implicitly {0}) + EvSTWDone: {"STWDone", 1005, false, []string{}, nil}, EvGCSweepStart: {"GCSweepStart", 1005, true, []string{}, nil}, EvGCSweepDone: {"GCSweepDone", 1005, false, []string{"swept", "reclaimed"}, nil}, // before 1.9, format was {} EvGoCreate: {"GoCreate", 1005, true, []string{"g", "stack"}, nil}, @@ -1140,3 +1151,24 @@ var EventDescriptions = [EvCount]struct { EvUserLog: {"UserLog", 1011, true, []string{"id", "keyid"}, []string{"category", "message"}}, EvCPUSample: {"CPUSample", 1019, true, []string{"ts", "p", "g"}, nil}, } + +// Copied from src/runtime/proc.go:stwReasonStrings in Go 1.21. +var stwReasonStringsGo121 = [...]string{ + "unknown", + "GC mark termination", + "GC sweep termination", + "write heap dump", + "goroutine profile", + "goroutine profile cleanup", + "all goroutines stack trace", + "read mem stats", + "AllThreadsSyscall", + "GOMAXPROCS", + "start trace", + "stop trace", + "CountPagesInUse (test)", + "ReadMetricsSlow (test)", + "ReadMemStatsSlow (test)", + "PageCachePagesLeaked (test)", + "ResetDebugLog (test)", +} diff --git a/src/internal/trace/parser_test.go b/src/internal/trace/parser_test.go index cdab95a59e..fce660c289 100644 --- a/src/internal/trace/parser_test.go +++ b/src/internal/trace/parser_test.go @@ -52,12 +52,13 @@ func TestParseCanned(t *testing.T) { } // Instead of Parse that requires a proper binary name for old traces, // we use 'parse' that omits symbol lookup if an empty string is given. - _, _, err = parse(bytes.NewReader(data), "") + ver, res, err := parse(bytes.NewReader(data), "") switch { case strings.HasSuffix(f.Name(), "_good"): if err != nil { t.Errorf("failed to parse good trace %v: %v", f.Name(), err) } + checkTrace(t, ver, res) case strings.HasSuffix(f.Name(), "_unordered"): if err != ErrTimeOrder { t.Errorf("unordered trace is not detected %v: %v", f.Name(), err) @@ -68,6 +69,18 @@ func TestParseCanned(t *testing.T) { } } +// checkTrace walks over a good trace and makes a bunch of additional checks +// that may not cause the parser to outright fail. +func checkTrace(t *testing.T, ver int, res ParseResult) { + for _, ev := range res.Events { + if ver >= 1021 { + if ev.Type == EvSTWStart && ev.SArgs[0] == "unknown" { + t.Errorf("found unknown STW event; update stwReasonStrings?") + } + } + } +} + func TestParseVersion(t *testing.T) { tests := map[string]int{ "go 1.5 trace\x00\x00\x00\x00": 1005, diff --git a/src/internal/trace/testdata/http_1_21_good b/src/internal/trace/testdata/http_1_21_good new file mode 100644 index 0000000000..b3295f9e5d Binary files /dev/null and b/src/internal/trace/testdata/http_1_21_good differ diff --git a/src/internal/trace/testdata/stress_1_21_good b/src/internal/trace/testdata/stress_1_21_good new file mode 100644 index 0000000000..1ade5e0eb6 Binary files /dev/null and b/src/internal/trace/testdata/stress_1_21_good differ diff --git a/src/internal/trace/testdata/stress_start_stop_1_21_good b/src/internal/trace/testdata/stress_start_stop_1_21_good new file mode 100644 index 0000000000..fff46a9a07 Binary files /dev/null and b/src/internal/trace/testdata/stress_start_stop_1_21_good differ diff --git a/src/internal/trace/testdata/user_task_region_1_21_good b/src/internal/trace/testdata/user_task_region_1_21_good new file mode 100644 index 0000000000..5c01a6405d Binary files /dev/null and b/src/internal/trace/testdata/user_task_region_1_21_good differ diff --git a/src/runtime/debug.go b/src/runtime/debug.go index 669c36f0d5..9a92b45ff3 100644 --- a/src/runtime/debug.go +++ b/src/runtime/debug.go @@ -25,7 +25,7 @@ func GOMAXPROCS(n int) int { return ret } - stopTheWorldGC("GOMAXPROCS") + stopTheWorldGC(stwGOMAXPROCS) // newprocs will be processed by startTheWorld newprocs = int32(n) diff --git a/src/runtime/export_debuglog_test.go b/src/runtime/export_debuglog_test.go index c9dfdcb393..f12aab00de 100644 --- a/src/runtime/export_debuglog_test.go +++ b/src/runtime/export_debuglog_test.go @@ -35,7 +35,7 @@ func DumpDebugLog() string { } func ResetDebugLog() { - stopTheWorld("ResetDebugLog") + stopTheWorld(stwForTestResetDebugLog) for l := allDloggers; l != nil; l = l.allLink { l.w.write = 0 l.w.tick, l.w.nano = 0, 0 diff --git a/src/runtime/export_test.go b/src/runtime/export_test.go index c04b76ee44..db91bc650d 100644 --- a/src/runtime/export_test.go +++ b/src/runtime/export_test.go @@ -276,7 +276,7 @@ var ReadUnaligned32 = readUnaligned32 var ReadUnaligned64 = readUnaligned64 func CountPagesInUse() (pagesInUse, counted uintptr) { - stopTheWorld("CountPagesInUse") + stopTheWorld(stwForTestCountPagesInUse) pagesInUse = uintptr(mheap_.pagesInUse.Load()) @@ -319,7 +319,7 @@ func (p *ProfBuf) Close() { } func ReadMetricsSlow(memStats *MemStats, samplesp unsafe.Pointer, len, cap int) { - stopTheWorld("ReadMetricsSlow") + stopTheWorld(stwForTestReadMetricsSlow) // Initialize the metrics beforehand because this could // allocate and skew the stats. @@ -347,7 +347,7 @@ func ReadMetricsSlow(memStats *MemStats, samplesp unsafe.Pointer, len, cap int) // ReadMemStatsSlow returns both the runtime-computed MemStats and // MemStats accumulated by scanning the heap. func ReadMemStatsSlow() (base, slow MemStats) { - stopTheWorld("ReadMemStatsSlow") + stopTheWorld(stwForTestReadMemStatsSlow) // Run on the system stack to avoid stack growth allocation. systemstack(func() { @@ -1193,7 +1193,7 @@ func CheckScavengedBitsCleared(mismatches []BitsMismatch) (n int, ok bool) { } func PageCachePagesLeaked() (leaked uintptr) { - stopTheWorld("PageCachePagesLeaked") + stopTheWorld(stwForTestPageCachePagesLeaked) // Walk over destroyed Ps and look for unflushed caches. deadp := allp[len(allp):cap(allp)] diff --git a/src/runtime/heapdump.go b/src/runtime/heapdump.go index e3f801129e..8ddec8b2d5 100644 --- a/src/runtime/heapdump.go +++ b/src/runtime/heapdump.go @@ -19,7 +19,7 @@ import ( //go:linkname runtime_debug_WriteHeapDump runtime/debug.WriteHeapDump func runtime_debug_WriteHeapDump(fd uintptr) { - stopTheWorld("write heap dump") + stopTheWorld(stwWriteHeapDump) // Keep m on this G's stack instead of the system stack. // Both readmemstats_m and writeheapdump_m have pretty large diff --git a/src/runtime/mgc.go b/src/runtime/mgc.go index bb60a3c447..599f688e6f 100644 --- a/src/runtime/mgc.go +++ b/src/runtime/mgc.go @@ -658,10 +658,7 @@ func gcStart(trigger gcTrigger) { now := nanotime() work.tSweepTerm = now work.pauseStart = now - if traceEnabled() { - traceGCSTWStart(1) - } - systemstack(stopTheWorldWithSema) + systemstack(func() { stopTheWorldWithSema(stwGCSweepTerm) }) // Finish sweep before we start concurrent scan. systemstack(func() { finishsweep_m() @@ -726,7 +723,7 @@ func gcStart(trigger gcTrigger) { // Concurrent mark. systemstack(func() { - now = startTheWorldWithSema(traceEnabled()) + now = startTheWorldWithSema() work.pauseNS += now - work.pauseStart work.tMark = now memstats.gcPauseDist.record(now - work.pauseStart) @@ -848,10 +845,7 @@ top: work.tMarkTerm = now work.pauseStart = now getg().m.preemptoff = "gcing" - if traceEnabled() { - traceGCSTWStart(0) - } - systemstack(stopTheWorldWithSema) + systemstack(func() { stopTheWorldWithSema(stwGCMarkTerm) }) // The gcphase is _GCmark, it will transition to _GCmarktermination // below. The important thing is that the wb remains active until // all marking is complete. This includes writes made by the GC. @@ -878,7 +872,7 @@ top: if restart { getg().m.preemptoff = "" systemstack(func() { - now := startTheWorldWithSema(traceEnabled()) + now := startTheWorldWithSema() work.pauseNS += now - work.pauseStart memstats.gcPauseDist.record(now - work.pauseStart) }) @@ -1092,7 +1086,7 @@ func gcMarkTermination() { throw("failed to set sweep barrier") } - systemstack(func() { startTheWorldWithSema(traceEnabled()) }) + systemstack(func() { startTheWorldWithSema() }) // Flush the heap profile so we can start a new cycle next GC. // This is relatively expensive, so we don't do it with the diff --git a/src/runtime/mprof.go b/src/runtime/mprof.go index 174ceb0a1f..308ebaebe6 100644 --- a/src/runtime/mprof.go +++ b/src/runtime/mprof.go @@ -901,7 +901,7 @@ func goroutineProfileWithLabelsConcurrent(p []StackRecord, labels []unsafe.Point ourg := getg() - stopTheWorld("profile") + stopTheWorld(stwGoroutineProfile) // Using gcount while the world is stopped should give us a consistent view // of the number of live goroutines, minus the number of goroutines that are // alive and permanently marked as "system". But to make this count agree @@ -966,7 +966,7 @@ func goroutineProfileWithLabelsConcurrent(p []StackRecord, labels []unsafe.Point tryRecordGoroutineProfile(gp1, Gosched) }) - stopTheWorld("profile cleanup") + stopTheWorld(stwGoroutineProfileCleanup) endOffset := goroutineProfile.offset.Swap(0) goroutineProfile.active = false goroutineProfile.records = nil @@ -1101,7 +1101,7 @@ func goroutineProfileWithLabelsSync(p []StackRecord, labels []unsafe.Pointer) (n return gp1 != gp && readgstatus(gp1) != _Gdead && !isSystemGoroutine(gp1, false) } - stopTheWorld("profile") + stopTheWorld(stwGoroutineProfile) // World is stopped, no locking required. n = 1 @@ -1187,7 +1187,7 @@ func saveg(pc, sp uintptr, gp *g, r *StackRecord) { // into buf after the trace for the current goroutine. func Stack(buf []byte, all bool) int { if all { - stopTheWorld("stack trace") + stopTheWorld(stwAllGoroutinesStack) } n := 0 diff --git a/src/runtime/mstats.go b/src/runtime/mstats.go index 3a5273f361..3c17c0b29e 100644 --- a/src/runtime/mstats.go +++ b/src/runtime/mstats.go @@ -347,7 +347,7 @@ func init() { // which is a snapshot as of the most recently completed garbage // collection cycle. func ReadMemStats(m *MemStats) { - stopTheWorld("read mem stats") + stopTheWorld(stwReadMemStats) systemstack(func() { readmemstats_m(m) diff --git a/src/runtime/os_linux.go b/src/runtime/os_linux.go index b0246e5c9f..f407e6a707 100644 --- a/src/runtime/os_linux.go +++ b/src/runtime/os_linux.go @@ -739,7 +739,7 @@ func syscall_runtime_doAllThreadsSyscall(trap, a1, a2, a3, a4, a5, a6 uintptr) ( // N.B. Internally, this function does not depend on STW to // successfully change every thread. It is only needed for user // expectations, per above. - stopTheWorld("doAllThreadsSyscall") + stopTheWorld(stwAllThreadsSyscall) // This function depends on several properties: // diff --git a/src/runtime/proc.go b/src/runtime/proc.go index 35aeb2d1ac..845e25da6e 100644 --- a/src/runtime/proc.go +++ b/src/runtime/proc.go @@ -1157,6 +1157,59 @@ func casGFromPreempted(gp *g, old, new uint32) bool { return gp.atomicstatus.CompareAndSwap(_Gpreempted, _Gwaiting) } +// stwReason is an enumeration of reasons the world is stopping. +type stwReason uint8 + +// Reasons to stop-the-world. +// +// Avoid reusing reasons and add new ones instead. +const ( + stwUnknown stwReason = iota // "unknown" + stwGCMarkTerm // "GC mark termination" + stwGCSweepTerm // "GC sweep termination" + stwWriteHeapDump // "write heap dump" + stwGoroutineProfile // "goroutine profile" + stwGoroutineProfileCleanup // "goroutine profile cleanup" + stwAllGoroutinesStack // "all goroutines stack trace" + stwReadMemStats // "read mem stats" + stwAllThreadsSyscall // "AllThreadsSyscall" + stwGOMAXPROCS // "GOMAXPROCS" + stwStartTrace // "start trace" + stwStopTrace // "stop trace" + stwForTestCountPagesInUse // "CountPagesInUse (test)" + stwForTestReadMetricsSlow // "ReadMetricsSlow (test)" + stwForTestReadMemStatsSlow // "ReadMemStatsSlow (test)" + stwForTestPageCachePagesLeaked // "PageCachePagesLeaked (test)" + stwForTestResetDebugLog // "ResetDebugLog (test)" +) + +func (r stwReason) String() string { + return stwReasonStrings[r] +} + +// If you add to this list, also add it to src/internal/trace/parser.go. +// If you change the values of any of the stw* constants, bump the trace +// version number and make a copy of this. +var stwReasonStrings = [...]string{ + stwUnknown: "unknown", + stwGCMarkTerm: "GC mark termination", + stwGCSweepTerm: "GC sweep termination", + stwWriteHeapDump: "write heap dump", + stwGoroutineProfile: "goroutine profile", + stwGoroutineProfileCleanup: "goroutine profile cleanup", + stwAllGoroutinesStack: "all goroutines stack trace", + stwReadMemStats: "read mem stats", + stwAllThreadsSyscall: "AllThreadsSyscall", + stwGOMAXPROCS: "GOMAXPROCS", + stwStartTrace: "start trace", + stwStopTrace: "stop trace", + stwForTestCountPagesInUse: "CountPagesInUse (test)", + stwForTestReadMetricsSlow: "ReadMetricsSlow (test)", + stwForTestReadMemStatsSlow: "ReadMemStatsSlow (test)", + stwForTestPageCachePagesLeaked: "PageCachePagesLeaked (test)", + stwForTestResetDebugLog: "ResetDebugLog (test)", +} + // stopTheWorld stops all P's from executing goroutines, interrupting // all goroutines at GC safe points and records reason as the reason // for the stop. On return, only the current goroutine's P is running. @@ -1171,10 +1224,10 @@ func casGFromPreempted(gp *g, old, new uint32) bool { // This is also used by routines that do stack dumps. If the system is // in panic or being exited, this may not reliably stop all // goroutines. -func stopTheWorld(reason string) { +func stopTheWorld(reason stwReason) { semacquire(&worldsema) gp := getg() - gp.m.preemptoff = reason + gp.m.preemptoff = reason.String() systemstack(func() { // Mark the goroutine which called stopTheWorld preemptible so its // stack may be scanned. @@ -1188,14 +1241,14 @@ func stopTheWorld(reason string) { // have already completed by the time we exit. // Don't provide a wait reason because we're still executing. casGToWaiting(gp, _Grunning, waitReasonStoppingTheWorld) - stopTheWorldWithSema() + stopTheWorldWithSema(reason) casgstatus(gp, _Gwaiting, _Grunning) }) } // startTheWorld undoes the effects of stopTheWorld. func startTheWorld() { - systemstack(func() { startTheWorldWithSema(false) }) + systemstack(func() { startTheWorldWithSema() }) // worldsema must be held over startTheWorldWithSema to ensure // gomaxprocs cannot change while worldsema is held. @@ -1221,7 +1274,7 @@ func startTheWorld() { // stopTheWorldGC has the same effect as stopTheWorld, but blocks // until the GC is not running. It also blocks a GC from starting // until startTheWorldGC is called. -func stopTheWorldGC(reason string) { +func stopTheWorldGC(reason stwReason) { semacquire(&gcsema) stopTheWorld(reason) } @@ -1265,7 +1318,10 @@ var gcsema uint32 = 1 // startTheWorldWithSema and stopTheWorldWithSema. // Holding worldsema causes any other goroutines invoking // stopTheWorld to block. -func stopTheWorldWithSema() { +func stopTheWorldWithSema(reason stwReason) { + if traceEnabled() { + traceSTWStart(reason) + } gp := getg() // If we hold a lock, then we won't be able to stop another M @@ -1344,7 +1400,7 @@ func stopTheWorldWithSema() { worldStopped() } -func startTheWorldWithSema(emitTraceEvent bool) int64 { +func startTheWorldWithSema() int64 { assertWorldStopped() mp := acquirem() // disable preemption because it can be holding p in a local var @@ -1388,8 +1444,8 @@ func startTheWorldWithSema(emitTraceEvent bool) int64 { // Capture start-the-world time before doing clean-up tasks. startTime := nanotime() - if emitTraceEvent { - traceGCSTWDone() + if traceEnabled() { + traceSTWDone() } // Wakeup an additional proc in case we have excessive runnable goroutines diff --git a/src/runtime/trace.go b/src/runtime/trace.go index 45a066e7a2..2fe6d2d13f 100644 --- a/src/runtime/trace.go +++ b/src/runtime/trace.go @@ -31,8 +31,8 @@ const ( traceEvProcStop = 6 // stop of P [timestamp] traceEvGCStart = 7 // GC start [timestamp, seq, stack id] traceEvGCDone = 8 // GC done [timestamp] - traceEvGCSTWStart = 9 // GC STW start [timestamp, kind] - traceEvGCSTWDone = 10 // GC STW done [timestamp] + traceEvSTWStart = 9 // STW start [timestamp, kind] + traceEvSTWDone = 10 // STW done [timestamp] traceEvGCSweepStart = 11 // GC sweep start [timestamp, stack id] traceEvGCSweepDone = 12 // GC sweep done [timestamp, swept, reclaimed] traceEvGoCreate = 13 // goroutine creation [timestamp, new goroutine id, new stack id, stack id] @@ -171,7 +171,8 @@ type gTraceState struct { // mTraceState is per-M state for the tracer. type mTraceState struct { - startingTrace bool // this M is in TraceStart, potentially before traceEnabled is true + startingTrace bool // this M is in TraceStart, potentially before traceEnabled is true + tracedSTWStart bool // this M traced a STW start, so it should trace an end } // pTraceState is per-P state for the tracer. @@ -247,7 +248,7 @@ func StartTrace() error { // Do not stop the world during GC so we ensure we always see // a consistent view of GC-related events (e.g. a start is always // paired with an end). - stopTheWorldGC("start tracing") + stopTheWorldGC(stwStartTrace) // Prevent sysmon from running any code that could generate events. lock(&sched.sysmonlock) @@ -377,7 +378,7 @@ func StartTrace() error { func StopTrace() { // Stop the world so that we can collect the trace buffers from all p's below, // and also to avoid races with traceEvent. - stopTheWorldGC("stop tracing") + stopTheWorldGC(stwStopTrace) // See the comment in StartTrace. lock(&sched.sysmonlock) @@ -560,7 +561,7 @@ func readTrace0() (buf []byte, park bool) { trace.headerWritten = true trace.lockOwner = nil unlock(&trace.lock) - return []byte("go 1.19 trace\x00\x00\x00"), false + return []byte("go 1.21 trace\x00\x00\x00"), false } // Optimistically look for CPU profile samples. This may write new stack // records, and may write new tracing buffers. @@ -1485,12 +1486,23 @@ func traceGCDone() { traceEvent(traceEvGCDone, -1) } -func traceGCSTWStart(kind int) { - traceEvent(traceEvGCSTWStart, -1, uint64(kind)) +func traceSTWStart(reason stwReason) { + // Don't trace if this STW is for trace start/stop, since traceEnabled + // switches during a STW. + if reason == stwStartTrace || reason == stwStopTrace { + return + } + getg().m.trace.tracedSTWStart = true + traceEvent(traceEvSTWStart, -1, uint64(reason)) } -func traceGCSTWDone() { - traceEvent(traceEvGCSTWDone, -1) +func traceSTWDone() { + mp := getg().m + if !mp.trace.tracedSTWStart { + return + } + mp.trace.tracedSTWStart = false + traceEvent(traceEvSTWDone, -1) } // traceGCSweepStart prepares to trace a sweep loop. This does not