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Diffstat (limited to 'src/runtime/trace.go')
| -rw-r--r-- | src/runtime/trace.go | 1260 |
1 files changed, 1260 insertions, 0 deletions
diff --git a/src/runtime/trace.go b/src/runtime/trace.go new file mode 100644 index 0000000..8f60de2 --- /dev/null +++ b/src/runtime/trace.go @@ -0,0 +1,1260 @@ +// Copyright 2014 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// Go execution tracer. +// The tracer captures a wide range of execution events like goroutine +// creation/blocking/unblocking, syscall enter/exit/block, GC-related events, +// changes of heap size, processor start/stop, etc and writes them to a buffer +// in a compact form. A precise nanosecond-precision timestamp and a stack +// trace is captured for most events. +// See https://golang.org/s/go15trace for more info. + +package runtime + +import ( + "internal/goarch" + "runtime/internal/atomic" + "runtime/internal/sys" + "unsafe" +) + +// Event types in the trace, args are given in square brackets. +const ( + traceEvNone = 0 // unused + traceEvBatch = 1 // start of per-P batch of events [pid, timestamp] + traceEvFrequency = 2 // contains tracer timer frequency [frequency (ticks per second)] + traceEvStack = 3 // stack [stack id, number of PCs, array of {PC, func string ID, file string ID, line}] + traceEvGomaxprocs = 4 // current value of GOMAXPROCS [timestamp, GOMAXPROCS, stack id] + traceEvProcStart = 5 // start of P [timestamp, thread id] + 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] + 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] + traceEvGoStart = 14 // goroutine starts running [timestamp, goroutine id, seq] + traceEvGoEnd = 15 // goroutine ends [timestamp] + traceEvGoStop = 16 // goroutine stops (like in select{}) [timestamp, stack] + traceEvGoSched = 17 // goroutine calls Gosched [timestamp, stack] + traceEvGoPreempt = 18 // goroutine is preempted [timestamp, stack] + traceEvGoSleep = 19 // goroutine calls Sleep [timestamp, stack] + traceEvGoBlock = 20 // goroutine blocks [timestamp, stack] + traceEvGoUnblock = 21 // goroutine is unblocked [timestamp, goroutine id, seq, stack] + traceEvGoBlockSend = 22 // goroutine blocks on chan send [timestamp, stack] + traceEvGoBlockRecv = 23 // goroutine blocks on chan recv [timestamp, stack] + traceEvGoBlockSelect = 24 // goroutine blocks on select [timestamp, stack] + traceEvGoBlockSync = 25 // goroutine blocks on Mutex/RWMutex [timestamp, stack] + traceEvGoBlockCond = 26 // goroutine blocks on Cond [timestamp, stack] + traceEvGoBlockNet = 27 // goroutine blocks on network [timestamp, stack] + traceEvGoSysCall = 28 // syscall enter [timestamp, stack] + traceEvGoSysExit = 29 // syscall exit [timestamp, goroutine id, seq, real timestamp] + traceEvGoSysBlock = 30 // syscall blocks [timestamp] + traceEvGoWaiting = 31 // denotes that goroutine is blocked when tracing starts [timestamp, goroutine id] + traceEvGoInSyscall = 32 // denotes that goroutine is in syscall when tracing starts [timestamp, goroutine id] + traceEvHeapAlloc = 33 // gcController.heapLive change [timestamp, heap_alloc] + traceEvHeapGoal = 34 // gcController.heapGoal (formerly next_gc) change [timestamp, heap goal in bytes] + traceEvTimerGoroutine = 35 // not currently used; previously denoted timer goroutine [timer goroutine id] + traceEvFutileWakeup = 36 // denotes that the previous wakeup of this goroutine was futile [timestamp] + traceEvString = 37 // string dictionary entry [ID, length, string] + traceEvGoStartLocal = 38 // goroutine starts running on the same P as the last event [timestamp, goroutine id] + traceEvGoUnblockLocal = 39 // goroutine is unblocked on the same P as the last event [timestamp, goroutine id, stack] + traceEvGoSysExitLocal = 40 // syscall exit on the same P as the last event [timestamp, goroutine id, real timestamp] + traceEvGoStartLabel = 41 // goroutine starts running with label [timestamp, goroutine id, seq, label string id] + traceEvGoBlockGC = 42 // goroutine blocks on GC assist [timestamp, stack] + traceEvGCMarkAssistStart = 43 // GC mark assist start [timestamp, stack] + traceEvGCMarkAssistDone = 44 // GC mark assist done [timestamp] + traceEvUserTaskCreate = 45 // trace.NewContext [timestamp, internal task id, internal parent task id, stack, name string] + traceEvUserTaskEnd = 46 // end of a task [timestamp, internal task id, stack] + traceEvUserRegion = 47 // trace.WithRegion [timestamp, internal task id, mode(0:start, 1:end), stack, name string] + traceEvUserLog = 48 // trace.Log [timestamp, internal task id, key string id, stack, value string] + traceEvCount = 49 + // Byte is used but only 6 bits are available for event type. + // The remaining 2 bits are used to specify the number of arguments. + // That means, the max event type value is 63. +) + +const ( + // Timestamps in trace are cputicks/traceTickDiv. + // This makes absolute values of timestamp diffs smaller, + // and so they are encoded in less number of bytes. + // 64 on x86 is somewhat arbitrary (one tick is ~20ns on a 3GHz machine). + // The suggested increment frequency for PowerPC's time base register is + // 512 MHz according to Power ISA v2.07 section 6.2, so we use 16 on ppc64 + // and ppc64le. + // Tracing won't work reliably for architectures where cputicks is emulated + // by nanotime, so the value doesn't matter for those architectures. + traceTickDiv = 16 + 48*(goarch.Is386|goarch.IsAmd64) + // Maximum number of PCs in a single stack trace. + // Since events contain only stack id rather than whole stack trace, + // we can allow quite large values here. + traceStackSize = 128 + // Identifier of a fake P that is used when we trace without a real P. + traceGlobProc = -1 + // Maximum number of bytes to encode uint64 in base-128. + traceBytesPerNumber = 10 + // Shift of the number of arguments in the first event byte. + traceArgCountShift = 6 + // Flag passed to traceGoPark to denote that the previous wakeup of this + // goroutine was futile. For example, a goroutine was unblocked on a mutex, + // but another goroutine got ahead and acquired the mutex before the first + // goroutine is scheduled, so the first goroutine has to block again. + // Such wakeups happen on buffered channels and sync.Mutex, + // but are generally not interesting for end user. + traceFutileWakeup byte = 128 +) + +// trace is global tracing context. +var trace struct { + lock mutex // protects the following members + lockOwner *g // to avoid deadlocks during recursive lock locks + enabled bool // when set runtime traces events + shutdown bool // set when we are waiting for trace reader to finish after setting enabled to false + headerWritten bool // whether ReadTrace has emitted trace header + footerWritten bool // whether ReadTrace has emitted trace footer + shutdownSema uint32 // used to wait for ReadTrace completion + seqStart uint64 // sequence number when tracing was started + ticksStart int64 // cputicks when tracing was started + ticksEnd int64 // cputicks when tracing was stopped + timeStart int64 // nanotime when tracing was started + timeEnd int64 // nanotime when tracing was stopped + seqGC uint64 // GC start/done sequencer + reading traceBufPtr // buffer currently handed off to user + empty traceBufPtr // stack of empty buffers + fullHead traceBufPtr // queue of full buffers + fullTail traceBufPtr + reader guintptr // goroutine that called ReadTrace, or nil + stackTab traceStackTable // maps stack traces to unique ids + + // Dictionary for traceEvString. + // + // TODO: central lock to access the map is not ideal. + // option: pre-assign ids to all user annotation region names and tags + // option: per-P cache + // option: sync.Map like data structure + stringsLock mutex + strings map[string]uint64 + stringSeq uint64 + + // markWorkerLabels maps gcMarkWorkerMode to string ID. + markWorkerLabels [len(gcMarkWorkerModeStrings)]uint64 + + bufLock mutex // protects buf + buf traceBufPtr // global trace buffer, used when running without a p +} + +// traceBufHeader is per-P tracing buffer. +type traceBufHeader struct { + link traceBufPtr // in trace.empty/full + lastTicks uint64 // when we wrote the last event + pos int // next write offset in arr + stk [traceStackSize]uintptr // scratch buffer for traceback +} + +// traceBuf is per-P tracing buffer. +// +//go:notinheap +type traceBuf struct { + traceBufHeader + arr [64<<10 - unsafe.Sizeof(traceBufHeader{})]byte // underlying buffer for traceBufHeader.buf +} + +// traceBufPtr is a *traceBuf that is not traced by the garbage +// collector and doesn't have write barriers. traceBufs are not +// allocated from the GC'd heap, so this is safe, and are often +// manipulated in contexts where write barriers are not allowed, so +// this is necessary. +// +// TODO: Since traceBuf is now go:notinheap, this isn't necessary. +type traceBufPtr uintptr + +func (tp traceBufPtr) ptr() *traceBuf { return (*traceBuf)(unsafe.Pointer(tp)) } +func (tp *traceBufPtr) set(b *traceBuf) { *tp = traceBufPtr(unsafe.Pointer(b)) } +func traceBufPtrOf(b *traceBuf) traceBufPtr { + return traceBufPtr(unsafe.Pointer(b)) +} + +// StartTrace enables tracing for the current process. +// While tracing, the data will be buffered and available via ReadTrace. +// StartTrace returns an error if tracing is already enabled. +// Most clients should use the runtime/trace package or the testing package's +// -test.trace flag instead of calling StartTrace directly. +func StartTrace() error { + // Stop the world so that we can take a consistent snapshot + // of all goroutines at the beginning of the trace. + // 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") + + // Prevent sysmon from running any code that could generate events. + lock(&sched.sysmonlock) + + // We are in stop-the-world, but syscalls can finish and write to trace concurrently. + // Exitsyscall could check trace.enabled long before and then suddenly wake up + // and decide to write to trace at a random point in time. + // However, such syscall will use the global trace.buf buffer, because we've + // acquired all p's by doing stop-the-world. So this protects us from such races. + lock(&trace.bufLock) + + if trace.enabled || trace.shutdown { + unlock(&trace.bufLock) + unlock(&sched.sysmonlock) + startTheWorldGC() + return errorString("tracing is already enabled") + } + + // Can't set trace.enabled yet. While the world is stopped, exitsyscall could + // already emit a delayed event (see exitTicks in exitsyscall) if we set trace.enabled here. + // That would lead to an inconsistent trace: + // - either GoSysExit appears before EvGoInSyscall, + // - or GoSysExit appears for a goroutine for which we don't emit EvGoInSyscall below. + // To instruct traceEvent that it must not ignore events below, we set startingtrace. + // trace.enabled is set afterwards once we have emitted all preliminary events. + _g_ := getg() + _g_.m.startingtrace = true + + // Obtain current stack ID to use in all traceEvGoCreate events below. + mp := acquirem() + stkBuf := make([]uintptr, traceStackSize) + stackID := traceStackID(mp, stkBuf, 2) + releasem(mp) + + // World is stopped, no need to lock. + forEachGRace(func(gp *g) { + status := readgstatus(gp) + if status != _Gdead { + gp.traceseq = 0 + gp.tracelastp = getg().m.p + // +PCQuantum because traceFrameForPC expects return PCs and subtracts PCQuantum. + id := trace.stackTab.put([]uintptr{startPCforTrace(gp.startpc) + sys.PCQuantum}) + traceEvent(traceEvGoCreate, -1, uint64(gp.goid), uint64(id), stackID) + } + if status == _Gwaiting { + // traceEvGoWaiting is implied to have seq=1. + gp.traceseq++ + traceEvent(traceEvGoWaiting, -1, uint64(gp.goid)) + } + if status == _Gsyscall { + gp.traceseq++ + traceEvent(traceEvGoInSyscall, -1, uint64(gp.goid)) + } else { + gp.sysblocktraced = false + } + }) + traceProcStart() + traceGoStart() + // Note: ticksStart needs to be set after we emit traceEvGoInSyscall events. + // If we do it the other way around, it is possible that exitsyscall will + // query sysexitticks after ticksStart but before traceEvGoInSyscall timestamp. + // It will lead to a false conclusion that cputicks is broken. + trace.ticksStart = cputicks() + trace.timeStart = nanotime() + trace.headerWritten = false + trace.footerWritten = false + + // string to id mapping + // 0 : reserved for an empty string + // remaining: other strings registered by traceString + trace.stringSeq = 0 + trace.strings = make(map[string]uint64) + + trace.seqGC = 0 + _g_.m.startingtrace = false + trace.enabled = true + + // Register runtime goroutine labels. + _, pid, bufp := traceAcquireBuffer() + for i, label := range gcMarkWorkerModeStrings[:] { + trace.markWorkerLabels[i], bufp = traceString(bufp, pid, label) + } + traceReleaseBuffer(pid) + + unlock(&trace.bufLock) + + unlock(&sched.sysmonlock) + + startTheWorldGC() + return nil +} + +// StopTrace stops tracing, if it was previously enabled. +// StopTrace only returns after all the reads for the trace have completed. +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") + + // See the comment in StartTrace. + lock(&sched.sysmonlock) + + // See the comment in StartTrace. + lock(&trace.bufLock) + + if !trace.enabled { + unlock(&trace.bufLock) + unlock(&sched.sysmonlock) + startTheWorldGC() + return + } + + traceGoSched() + + // Loop over all allocated Ps because dead Ps may still have + // trace buffers. + for _, p := range allp[:cap(allp)] { + buf := p.tracebuf + if buf != 0 { + traceFullQueue(buf) + p.tracebuf = 0 + } + } + if trace.buf != 0 { + buf := trace.buf + trace.buf = 0 + if buf.ptr().pos != 0 { + traceFullQueue(buf) + } + } + + for { + trace.ticksEnd = cputicks() + trace.timeEnd = nanotime() + // Windows time can tick only every 15ms, wait for at least one tick. + if trace.timeEnd != trace.timeStart { + break + } + osyield() + } + + trace.enabled = false + trace.shutdown = true + unlock(&trace.bufLock) + + unlock(&sched.sysmonlock) + + startTheWorldGC() + + // The world is started but we've set trace.shutdown, so new tracing can't start. + // Wait for the trace reader to flush pending buffers and stop. + semacquire(&trace.shutdownSema) + if raceenabled { + raceacquire(unsafe.Pointer(&trace.shutdownSema)) + } + + // The lock protects us from races with StartTrace/StopTrace because they do stop-the-world. + lock(&trace.lock) + for _, p := range allp[:cap(allp)] { + if p.tracebuf != 0 { + throw("trace: non-empty trace buffer in proc") + } + } + if trace.buf != 0 { + throw("trace: non-empty global trace buffer") + } + if trace.fullHead != 0 || trace.fullTail != 0 { + throw("trace: non-empty full trace buffer") + } + if trace.reading != 0 || trace.reader != 0 { + throw("trace: reading after shutdown") + } + for trace.empty != 0 { + buf := trace.empty + trace.empty = buf.ptr().link + sysFree(unsafe.Pointer(buf), unsafe.Sizeof(*buf.ptr()), &memstats.other_sys) + } + trace.strings = nil + trace.shutdown = false + unlock(&trace.lock) +} + +// ReadTrace returns the next chunk of binary tracing data, blocking until data +// is available. If tracing is turned off and all the data accumulated while it +// was on has been returned, ReadTrace returns nil. The caller must copy the +// returned data before calling ReadTrace again. +// ReadTrace must be called from one goroutine at a time. +func ReadTrace() []byte { + // This function may need to lock trace.lock recursively + // (goparkunlock -> traceGoPark -> traceEvent -> traceFlush). + // To allow this we use trace.lockOwner. + // Also this function must not allocate while holding trace.lock: + // allocation can call heap allocate, which will try to emit a trace + // event while holding heap lock. + lock(&trace.lock) + trace.lockOwner = getg() + + if trace.reader != 0 { + // More than one goroutine reads trace. This is bad. + // But we rather do not crash the program because of tracing, + // because tracing can be enabled at runtime on prod servers. + trace.lockOwner = nil + unlock(&trace.lock) + println("runtime: ReadTrace called from multiple goroutines simultaneously") + return nil + } + // Recycle the old buffer. + if buf := trace.reading; buf != 0 { + buf.ptr().link = trace.empty + trace.empty = buf + trace.reading = 0 + } + // Write trace header. + if !trace.headerWritten { + trace.headerWritten = true + trace.lockOwner = nil + unlock(&trace.lock) + return []byte("go 1.11 trace\x00\x00\x00") + } + // Wait for new data. + if trace.fullHead == 0 && !trace.shutdown { + trace.reader.set(getg()) + goparkunlock(&trace.lock, waitReasonTraceReaderBlocked, traceEvGoBlock, 2) + lock(&trace.lock) + } + // Write a buffer. + if trace.fullHead != 0 { + buf := traceFullDequeue() + trace.reading = buf + trace.lockOwner = nil + unlock(&trace.lock) + return buf.ptr().arr[:buf.ptr().pos] + } + // Write footer with timer frequency. + if !trace.footerWritten { + trace.footerWritten = true + // Use float64 because (trace.ticksEnd - trace.ticksStart) * 1e9 can overflow int64. + freq := float64(trace.ticksEnd-trace.ticksStart) * 1e9 / float64(trace.timeEnd-trace.timeStart) / traceTickDiv + if freq <= 0 { + throw("trace: ReadTrace got invalid frequency") + } + trace.lockOwner = nil + unlock(&trace.lock) + var data []byte + data = append(data, traceEvFrequency|0<<traceArgCountShift) + data = traceAppend(data, uint64(freq)) + // This will emit a bunch of full buffers, we will pick them up + // on the next iteration. + trace.stackTab.dump() + return data + } + // Done. + if trace.shutdown { + trace.lockOwner = nil + unlock(&trace.lock) + if raceenabled { + // Model synchronization on trace.shutdownSema, which race + // detector does not see. This is required to avoid false + // race reports on writer passed to trace.Start. + racerelease(unsafe.Pointer(&trace.shutdownSema)) + } + // trace.enabled is already reset, so can call traceable functions. + semrelease(&trace.shutdownSema) + return nil + } + // Also bad, but see the comment above. + trace.lockOwner = nil + unlock(&trace.lock) + println("runtime: spurious wakeup of trace reader") + return nil +} + +// traceReader returns the trace reader that should be woken up, if any. +func traceReader() *g { + if trace.reader == 0 || (trace.fullHead == 0 && !trace.shutdown) { + return nil + } + lock(&trace.lock) + if trace.reader == 0 || (trace.fullHead == 0 && !trace.shutdown) { + unlock(&trace.lock) + return nil + } + gp := trace.reader.ptr() + trace.reader.set(nil) + unlock(&trace.lock) + return gp +} + +// traceProcFree frees trace buffer associated with pp. +func traceProcFree(pp *p) { + buf := pp.tracebuf + pp.tracebuf = 0 + if buf == 0 { + return + } + lock(&trace.lock) + traceFullQueue(buf) + unlock(&trace.lock) +} + +// traceFullQueue queues buf into queue of full buffers. +func traceFullQueue(buf traceBufPtr) { + buf.ptr().link = 0 + if trace.fullHead == 0 { + trace.fullHead = buf + } else { + trace.fullTail.ptr().link = buf + } + trace.fullTail = buf +} + +// traceFullDequeue dequeues from queue of full buffers. +func traceFullDequeue() traceBufPtr { + buf := trace.fullHead + if buf == 0 { + return 0 + } + trace.fullHead = buf.ptr().link + if trace.fullHead == 0 { + trace.fullTail = 0 + } + buf.ptr().link = 0 + return buf +} + +// traceEvent writes a single event to trace buffer, flushing the buffer if necessary. +// ev is event type. +// If skip > 0, write current stack id as the last argument (skipping skip top frames). +// If skip = 0, this event type should contain a stack, but we don't want +// to collect and remember it for this particular call. +func traceEvent(ev byte, skip int, args ...uint64) { + mp, pid, bufp := traceAcquireBuffer() + // Double-check trace.enabled now that we've done m.locks++ and acquired bufLock. + // This protects from races between traceEvent and StartTrace/StopTrace. + + // The caller checked that trace.enabled == true, but trace.enabled might have been + // turned off between the check and now. Check again. traceLockBuffer did mp.locks++, + // StopTrace does stopTheWorld, and stopTheWorld waits for mp.locks to go back to zero, + // so if we see trace.enabled == true now, we know it's true for the rest of the function. + // Exitsyscall can run even during stopTheWorld. The race with StartTrace/StopTrace + // during tracing in exitsyscall is resolved by locking trace.bufLock in traceLockBuffer. + // + // Note trace_userTaskCreate runs the same check. + if !trace.enabled && !mp.startingtrace { + traceReleaseBuffer(pid) + return + } + + if skip > 0 { + if getg() == mp.curg { + skip++ // +1 because stack is captured in traceEventLocked. + } + } + traceEventLocked(0, mp, pid, bufp, ev, skip, args...) + traceReleaseBuffer(pid) +} + +func traceEventLocked(extraBytes int, mp *m, pid int32, bufp *traceBufPtr, ev byte, skip int, args ...uint64) { + buf := bufp.ptr() + // TODO: test on non-zero extraBytes param. + maxSize := 2 + 5*traceBytesPerNumber + extraBytes // event type, length, sequence, timestamp, stack id and two add params + if buf == nil || len(buf.arr)-buf.pos < maxSize { + buf = traceFlush(traceBufPtrOf(buf), pid).ptr() + bufp.set(buf) + } + + // NOTE: ticks might be same after tick division, although the real cputicks is + // linear growth. + ticks := uint64(cputicks()) / traceTickDiv + tickDiff := ticks - buf.lastTicks + if tickDiff == 0 { + ticks = buf.lastTicks + 1 + tickDiff = 1 + } + + buf.lastTicks = ticks + narg := byte(len(args)) + if skip >= 0 { + narg++ + } + // We have only 2 bits for number of arguments. + // If number is >= 3, then the event type is followed by event length in bytes. + if narg > 3 { + narg = 3 + } + startPos := buf.pos + buf.byte(ev | narg<<traceArgCountShift) + var lenp *byte + if narg == 3 { + // Reserve the byte for length assuming that length < 128. + buf.varint(0) + lenp = &buf.arr[buf.pos-1] + } + buf.varint(tickDiff) + for _, a := range args { + buf.varint(a) + } + if skip == 0 { + buf.varint(0) + } else if skip > 0 { + buf.varint(traceStackID(mp, buf.stk[:], skip)) + } + evSize := buf.pos - startPos + if evSize > maxSize { + throw("invalid length of trace event") + } + if lenp != nil { + // Fill in actual length. + *lenp = byte(evSize - 2) + } +} + +func traceStackID(mp *m, buf []uintptr, skip int) uint64 { + _g_ := getg() + gp := mp.curg + var nstk int + if gp == _g_ { + nstk = callers(skip+1, buf) + } else if gp != nil { + gp = mp.curg + nstk = gcallers(gp, skip, buf) + } + if nstk > 0 { + nstk-- // skip runtime.goexit + } + if nstk > 0 && gp.goid == 1 { + nstk-- // skip runtime.main + } + id := trace.stackTab.put(buf[:nstk]) + return uint64(id) +} + +// traceAcquireBuffer returns trace buffer to use and, if necessary, locks it. +func traceAcquireBuffer() (mp *m, pid int32, bufp *traceBufPtr) { + mp = acquirem() + if p := mp.p.ptr(); p != nil { + return mp, p.id, &p.tracebuf + } + lock(&trace.bufLock) + return mp, traceGlobProc, &trace.buf +} + +// traceReleaseBuffer releases a buffer previously acquired with traceAcquireBuffer. +func traceReleaseBuffer(pid int32) { + if pid == traceGlobProc { + unlock(&trace.bufLock) + } + releasem(getg().m) +} + +// traceFlush puts buf onto stack of full buffers and returns an empty buffer. +func traceFlush(buf traceBufPtr, pid int32) traceBufPtr { + owner := trace.lockOwner + dolock := owner == nil || owner != getg().m.curg + if dolock { + lock(&trace.lock) + } + if buf != 0 { + traceFullQueue(buf) + } + if trace.empty != 0 { + buf = trace.empty + trace.empty = buf.ptr().link + } else { + buf = traceBufPtr(sysAlloc(unsafe.Sizeof(traceBuf{}), &memstats.other_sys)) + if buf == 0 { + throw("trace: out of memory") + } + } + bufp := buf.ptr() + bufp.link.set(nil) + bufp.pos = 0 + + // initialize the buffer for a new batch + ticks := uint64(cputicks()) / traceTickDiv + if ticks == bufp.lastTicks { + ticks = bufp.lastTicks + 1 + } + bufp.lastTicks = ticks + bufp.byte(traceEvBatch | 1<<traceArgCountShift) + bufp.varint(uint64(pid)) + bufp.varint(ticks) + + if dolock { + unlock(&trace.lock) + } + return buf +} + +// traceString adds a string to the trace.strings and returns the id. +func traceString(bufp *traceBufPtr, pid int32, s string) (uint64, *traceBufPtr) { + if s == "" { + return 0, bufp + } + + lock(&trace.stringsLock) + if raceenabled { + // raceacquire is necessary because the map access + // below is race annotated. + raceacquire(unsafe.Pointer(&trace.stringsLock)) + } + + if id, ok := trace.strings[s]; ok { + if raceenabled { + racerelease(unsafe.Pointer(&trace.stringsLock)) + } + unlock(&trace.stringsLock) + + return id, bufp + } + + trace.stringSeq++ + id := trace.stringSeq + trace.strings[s] = id + + if raceenabled { + racerelease(unsafe.Pointer(&trace.stringsLock)) + } + unlock(&trace.stringsLock) + + // memory allocation in above may trigger tracing and + // cause *bufp changes. Following code now works with *bufp, + // so there must be no memory allocation or any activities + // that causes tracing after this point. + + buf := bufp.ptr() + size := 1 + 2*traceBytesPerNumber + len(s) + if buf == nil || len(buf.arr)-buf.pos < size { + buf = traceFlush(traceBufPtrOf(buf), pid).ptr() + bufp.set(buf) + } + buf.byte(traceEvString) + buf.varint(id) + + // double-check the string and the length can fit. + // Otherwise, truncate the string. + slen := len(s) + if room := len(buf.arr) - buf.pos; room < slen+traceBytesPerNumber { + slen = room + } + + buf.varint(uint64(slen)) + buf.pos += copy(buf.arr[buf.pos:], s[:slen]) + + bufp.set(buf) + return id, bufp +} + +// traceAppend appends v to buf in little-endian-base-128 encoding. +func traceAppend(buf []byte, v uint64) []byte { + for ; v >= 0x80; v >>= 7 { + buf = append(buf, 0x80|byte(v)) + } + buf = append(buf, byte(v)) + return buf +} + +// varint appends v to buf in little-endian-base-128 encoding. +func (buf *traceBuf) varint(v uint64) { + pos := buf.pos + for ; v >= 0x80; v >>= 7 { + buf.arr[pos] = 0x80 | byte(v) + pos++ + } + buf.arr[pos] = byte(v) + pos++ + buf.pos = pos +} + +// byte appends v to buf. +func (buf *traceBuf) byte(v byte) { + buf.arr[buf.pos] = v + buf.pos++ +} + +// traceStackTable maps stack traces (arrays of PC's) to unique uint32 ids. +// It is lock-free for reading. +type traceStackTable struct { + lock mutex + seq uint32 + mem traceAlloc + tab [1 << 13]traceStackPtr +} + +// traceStack is a single stack in traceStackTable. +type traceStack struct { + link traceStackPtr + hash uintptr + id uint32 + n int + stk [0]uintptr // real type [n]uintptr +} + +type traceStackPtr uintptr + +func (tp traceStackPtr) ptr() *traceStack { return (*traceStack)(unsafe.Pointer(tp)) } + +// stack returns slice of PCs. +func (ts *traceStack) stack() []uintptr { + return (*[traceStackSize]uintptr)(unsafe.Pointer(&ts.stk))[:ts.n] +} + +// put returns a unique id for the stack trace pcs and caches it in the table, +// if it sees the trace for the first time. +func (tab *traceStackTable) put(pcs []uintptr) uint32 { + if len(pcs) == 0 { + return 0 + } + hash := memhash(unsafe.Pointer(&pcs[0]), 0, uintptr(len(pcs))*unsafe.Sizeof(pcs[0])) + // First, search the hashtable w/o the mutex. + if id := tab.find(pcs, hash); id != 0 { + return id + } + // Now, double check under the mutex. + lock(&tab.lock) + if id := tab.find(pcs, hash); id != 0 { + unlock(&tab.lock) + return id + } + // Create new record. + tab.seq++ + stk := tab.newStack(len(pcs)) + stk.hash = hash + stk.id = tab.seq + stk.n = len(pcs) + stkpc := stk.stack() + for i, pc := range pcs { + stkpc[i] = pc + } + part := int(hash % uintptr(len(tab.tab))) + stk.link = tab.tab[part] + atomicstorep(unsafe.Pointer(&tab.tab[part]), unsafe.Pointer(stk)) + unlock(&tab.lock) + return stk.id +} + +// find checks if the stack trace pcs is already present in the table. +func (tab *traceStackTable) find(pcs []uintptr, hash uintptr) uint32 { + part := int(hash % uintptr(len(tab.tab))) +Search: + for stk := tab.tab[part].ptr(); stk != nil; stk = stk.link.ptr() { + if stk.hash == hash && stk.n == len(pcs) { + for i, stkpc := range stk.stack() { + if stkpc != pcs[i] { + continue Search + } + } + return stk.id + } + } + return 0 +} + +// newStack allocates a new stack of size n. +func (tab *traceStackTable) newStack(n int) *traceStack { + return (*traceStack)(tab.mem.alloc(unsafe.Sizeof(traceStack{}) + uintptr(n)*goarch.PtrSize)) +} + +// allFrames returns all of the Frames corresponding to pcs. +func allFrames(pcs []uintptr) []Frame { + frames := make([]Frame, 0, len(pcs)) + ci := CallersFrames(pcs) + for { + f, more := ci.Next() + frames = append(frames, f) + if !more { + return frames + } + } +} + +// dump writes all previously cached stacks to trace buffers, +// releases all memory and resets state. +func (tab *traceStackTable) dump() { + var tmp [(2 + 4*traceStackSize) * traceBytesPerNumber]byte + bufp := traceFlush(0, 0) + for _, stk := range tab.tab { + stk := stk.ptr() + for ; stk != nil; stk = stk.link.ptr() { + tmpbuf := tmp[:0] + tmpbuf = traceAppend(tmpbuf, uint64(stk.id)) + frames := allFrames(stk.stack()) + tmpbuf = traceAppend(tmpbuf, uint64(len(frames))) + for _, f := range frames { + var frame traceFrame + frame, bufp = traceFrameForPC(bufp, 0, f) + tmpbuf = traceAppend(tmpbuf, uint64(f.PC)) + tmpbuf = traceAppend(tmpbuf, uint64(frame.funcID)) + tmpbuf = traceAppend(tmpbuf, uint64(frame.fileID)) + tmpbuf = traceAppend(tmpbuf, uint64(frame.line)) + } + // Now copy to the buffer. + size := 1 + traceBytesPerNumber + len(tmpbuf) + if buf := bufp.ptr(); len(buf.arr)-buf.pos < size { + bufp = traceFlush(bufp, 0) + } + buf := bufp.ptr() + buf.byte(traceEvStack | 3<<traceArgCountShift) + buf.varint(uint64(len(tmpbuf))) + buf.pos += copy(buf.arr[buf.pos:], tmpbuf) + } + } + + lock(&trace.lock) + traceFullQueue(bufp) + unlock(&trace.lock) + + tab.mem.drop() + *tab = traceStackTable{} + lockInit(&((*tab).lock), lockRankTraceStackTab) +} + +type traceFrame struct { + funcID uint64 + fileID uint64 + line uint64 +} + +// traceFrameForPC records the frame information. +// It may allocate memory. +func traceFrameForPC(buf traceBufPtr, pid int32, f Frame) (traceFrame, traceBufPtr) { + bufp := &buf + var frame traceFrame + + fn := f.Function + const maxLen = 1 << 10 + if len(fn) > maxLen { + fn = fn[len(fn)-maxLen:] + } + frame.funcID, bufp = traceString(bufp, pid, fn) + frame.line = uint64(f.Line) + file := f.File + if len(file) > maxLen { + file = file[len(file)-maxLen:] + } + frame.fileID, bufp = traceString(bufp, pid, file) + return frame, (*bufp) +} + +// traceAlloc is a non-thread-safe region allocator. +// It holds a linked list of traceAllocBlock. +type traceAlloc struct { + head traceAllocBlockPtr + off uintptr +} + +// traceAllocBlock is a block in traceAlloc. +// +// traceAllocBlock is allocated from non-GC'd memory, so it must not +// contain heap pointers. Writes to pointers to traceAllocBlocks do +// not need write barriers. +// +//go:notinheap +type traceAllocBlock struct { + next traceAllocBlockPtr + data [64<<10 - goarch.PtrSize]byte +} + +// TODO: Since traceAllocBlock is now go:notinheap, this isn't necessary. +type traceAllocBlockPtr uintptr + +func (p traceAllocBlockPtr) ptr() *traceAllocBlock { return (*traceAllocBlock)(unsafe.Pointer(p)) } +func (p *traceAllocBlockPtr) set(x *traceAllocBlock) { *p = traceAllocBlockPtr(unsafe.Pointer(x)) } + +// alloc allocates n-byte block. +func (a *traceAlloc) alloc(n uintptr) unsafe.Pointer { + n = alignUp(n, goarch.PtrSize) + if a.head == 0 || a.off+n > uintptr(len(a.head.ptr().data)) { + if n > uintptr(len(a.head.ptr().data)) { + throw("trace: alloc too large") + } + block := (*traceAllocBlock)(sysAlloc(unsafe.Sizeof(traceAllocBlock{}), &memstats.other_sys)) + if block == nil { + throw("trace: out of memory") + } + block.next.set(a.head.ptr()) + a.head.set(block) + a.off = 0 + } + p := &a.head.ptr().data[a.off] + a.off += n + return unsafe.Pointer(p) +} + +// drop frees all previously allocated memory and resets the allocator. +func (a *traceAlloc) drop() { + for a.head != 0 { + block := a.head.ptr() + a.head.set(block.next.ptr()) + sysFree(unsafe.Pointer(block), unsafe.Sizeof(traceAllocBlock{}), &memstats.other_sys) + } +} + +// The following functions write specific events to trace. + +func traceGomaxprocs(procs int32) { + traceEvent(traceEvGomaxprocs, 1, uint64(procs)) +} + +func traceProcStart() { + traceEvent(traceEvProcStart, -1, uint64(getg().m.id)) +} + +func traceProcStop(pp *p) { + // Sysmon and stopTheWorld can stop Ps blocked in syscalls, + // to handle this we temporary employ the P. + mp := acquirem() + oldp := mp.p + mp.p.set(pp) + traceEvent(traceEvProcStop, -1) + mp.p = oldp + releasem(mp) +} + +func traceGCStart() { + traceEvent(traceEvGCStart, 3, trace.seqGC) + trace.seqGC++ +} + +func traceGCDone() { + traceEvent(traceEvGCDone, -1) +} + +func traceGCSTWStart(kind int) { + traceEvent(traceEvGCSTWStart, -1, uint64(kind)) +} + +func traceGCSTWDone() { + traceEvent(traceEvGCSTWDone, -1) +} + +// traceGCSweepStart prepares to trace a sweep loop. This does not +// emit any events until traceGCSweepSpan is called. +// +// traceGCSweepStart must be paired with traceGCSweepDone and there +// must be no preemption points between these two calls. +func traceGCSweepStart() { + // Delay the actual GCSweepStart event until the first span + // sweep. If we don't sweep anything, don't emit any events. + _p_ := getg().m.p.ptr() + if _p_.traceSweep { + throw("double traceGCSweepStart") + } + _p_.traceSweep, _p_.traceSwept, _p_.traceReclaimed = true, 0, 0 +} + +// traceGCSweepSpan traces the sweep of a single page. +// +// This may be called outside a traceGCSweepStart/traceGCSweepDone +// pair; however, it will not emit any trace events in this case. +func traceGCSweepSpan(bytesSwept uintptr) { + _p_ := getg().m.p.ptr() + if _p_.traceSweep { + if _p_.traceSwept == 0 { + traceEvent(traceEvGCSweepStart, 1) + } + _p_.traceSwept += bytesSwept + } +} + +func traceGCSweepDone() { + _p_ := getg().m.p.ptr() + if !_p_.traceSweep { + throw("missing traceGCSweepStart") + } + if _p_.traceSwept != 0 { + traceEvent(traceEvGCSweepDone, -1, uint64(_p_.traceSwept), uint64(_p_.traceReclaimed)) + } + _p_.traceSweep = false +} + +func traceGCMarkAssistStart() { + traceEvent(traceEvGCMarkAssistStart, 1) +} + +func traceGCMarkAssistDone() { + traceEvent(traceEvGCMarkAssistDone, -1) +} + +func traceGoCreate(newg *g, pc uintptr) { + newg.traceseq = 0 + newg.tracelastp = getg().m.p + // +PCQuantum because traceFrameForPC expects return PCs and subtracts PCQuantum. + id := trace.stackTab.put([]uintptr{startPCforTrace(pc) + sys.PCQuantum}) + traceEvent(traceEvGoCreate, 2, uint64(newg.goid), uint64(id)) +} + +func traceGoStart() { + _g_ := getg().m.curg + _p_ := _g_.m.p + _g_.traceseq++ + if _p_.ptr().gcMarkWorkerMode != gcMarkWorkerNotWorker { + traceEvent(traceEvGoStartLabel, -1, uint64(_g_.goid), _g_.traceseq, trace.markWorkerLabels[_p_.ptr().gcMarkWorkerMode]) + } else if _g_.tracelastp == _p_ { + traceEvent(traceEvGoStartLocal, -1, uint64(_g_.goid)) + } else { + _g_.tracelastp = _p_ + traceEvent(traceEvGoStart, -1, uint64(_g_.goid), _g_.traceseq) + } +} + +func traceGoEnd() { + traceEvent(traceEvGoEnd, -1) +} + +func traceGoSched() { + _g_ := getg() + _g_.tracelastp = _g_.m.p + traceEvent(traceEvGoSched, 1) +} + +func traceGoPreempt() { + _g_ := getg() + _g_.tracelastp = _g_.m.p + traceEvent(traceEvGoPreempt, 1) +} + +func traceGoPark(traceEv byte, skip int) { + if traceEv&traceFutileWakeup != 0 { + traceEvent(traceEvFutileWakeup, -1) + } + traceEvent(traceEv & ^traceFutileWakeup, skip) +} + +func traceGoUnpark(gp *g, skip int) { + _p_ := getg().m.p + gp.traceseq++ + if gp.tracelastp == _p_ { + traceEvent(traceEvGoUnblockLocal, skip, uint64(gp.goid)) + } else { + gp.tracelastp = _p_ + traceEvent(traceEvGoUnblock, skip, uint64(gp.goid), gp.traceseq) + } +} + +func traceGoSysCall() { + traceEvent(traceEvGoSysCall, 1) +} + +func traceGoSysExit(ts int64) { + if ts != 0 && ts < trace.ticksStart { + // There is a race between the code that initializes sysexitticks + // (in exitsyscall, which runs without a P, and therefore is not + // stopped with the rest of the world) and the code that initializes + // a new trace. The recorded sysexitticks must therefore be treated + // as "best effort". If they are valid for this trace, then great, + // use them for greater accuracy. But if they're not valid for this + // trace, assume that the trace was started after the actual syscall + // exit (but before we actually managed to start the goroutine, + // aka right now), and assign a fresh time stamp to keep the log consistent. + ts = 0 + } + _g_ := getg().m.curg + _g_.traceseq++ + _g_.tracelastp = _g_.m.p + traceEvent(traceEvGoSysExit, -1, uint64(_g_.goid), _g_.traceseq, uint64(ts)/traceTickDiv) +} + +func traceGoSysBlock(pp *p) { + // Sysmon and stopTheWorld can declare syscalls running on remote Ps as blocked, + // to handle this we temporary employ the P. + mp := acquirem() + oldp := mp.p + mp.p.set(pp) + traceEvent(traceEvGoSysBlock, -1) + mp.p = oldp + releasem(mp) +} + +func traceHeapAlloc() { + traceEvent(traceEvHeapAlloc, -1, gcController.heapLive) +} + +func traceHeapGoal() { + if heapGoal := atomic.Load64(&gcController.heapGoal); heapGoal == ^uint64(0) { + // Heap-based triggering is disabled. + traceEvent(traceEvHeapGoal, -1, 0) + } else { + traceEvent(traceEvHeapGoal, -1, heapGoal) + } +} + +// To access runtime functions from runtime/trace. +// See runtime/trace/annotation.go + +//go:linkname trace_userTaskCreate runtime/trace.userTaskCreate +func trace_userTaskCreate(id, parentID uint64, taskType string) { + if !trace.enabled { + return + } + + // Same as in traceEvent. + mp, pid, bufp := traceAcquireBuffer() + if !trace.enabled && !mp.startingtrace { + traceReleaseBuffer(pid) + return + } + + typeStringID, bufp := traceString(bufp, pid, taskType) + traceEventLocked(0, mp, pid, bufp, traceEvUserTaskCreate, 3, id, parentID, typeStringID) + traceReleaseBuffer(pid) +} + +//go:linkname trace_userTaskEnd runtime/trace.userTaskEnd +func trace_userTaskEnd(id uint64) { + traceEvent(traceEvUserTaskEnd, 2, id) +} + +//go:linkname trace_userRegion runtime/trace.userRegion +func trace_userRegion(id, mode uint64, name string) { + if !trace.enabled { + return + } + + mp, pid, bufp := traceAcquireBuffer() + if !trace.enabled && !mp.startingtrace { + traceReleaseBuffer(pid) + return + } + + nameStringID, bufp := traceString(bufp, pid, name) + traceEventLocked(0, mp, pid, bufp, traceEvUserRegion, 3, id, mode, nameStringID) + traceReleaseBuffer(pid) +} + +//go:linkname trace_userLog runtime/trace.userLog +func trace_userLog(id uint64, category, message string) { + if !trace.enabled { + return + } + + mp, pid, bufp := traceAcquireBuffer() + if !trace.enabled && !mp.startingtrace { + traceReleaseBuffer(pid) + return + } + + categoryID, bufp := traceString(bufp, pid, category) + + extraSpace := traceBytesPerNumber + len(message) // extraSpace for the value string + traceEventLocked(extraSpace, mp, pid, bufp, traceEvUserLog, 3, id, categoryID) + // traceEventLocked reserved extra space for val and len(val) + // in buf, so buf now has room for the following. + buf := bufp.ptr() + + // double-check the message and its length can fit. + // Otherwise, truncate the message. + slen := len(message) + if room := len(buf.arr) - buf.pos; room < slen+traceBytesPerNumber { + slen = room + } + buf.varint(uint64(slen)) + buf.pos += copy(buf.arr[buf.pos:], message[:slen]) + + traceReleaseBuffer(pid) +} + +// the start PC of a goroutine for tracing purposes. If pc is a wrapper, +// it returns the PC of the wrapped function. Otherwise it returns pc. +func startPCforTrace(pc uintptr) uintptr { + f := findfunc(pc) + if !f.valid() { + return pc // should not happen, but don't care + } + w := funcdata(f, _FUNCDATA_WrapInfo) + if w == nil { + return pc // not a wrapper + } + return f.datap.textAddr(*(*uint32)(w)) +} |