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// 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 (
"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 // memstats.heap_live change [timestamp, heap_alloc]
traceEvNextGC = 34 // memstats.next_gc change [timestamp, next_gc]
traceEvTimerGoroutine = 35 // denotes 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*(sys.Goarch386|sys.GoarchAmd64|sys.GoarchAmd64p32)
// 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.
stopTheWorld("start tracing")
// 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)
startTheWorld()
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)
for _, gp := range allgs {
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{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)
startTheWorld()
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.
stopTheWorld("stop tracing")
// See the comment in StartTrace.
lock(&trace.bufLock)
if !trace.enabled {
unlock(&trace.bufLock)
startTheWorld()
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)
startTheWorld()
// 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
trace.lockOwner = nil
unlock(&trace.lock)
var data []byte
data = append(data, traceEvFrequency|0<<traceArgCountShift)
data = traceAppend(data, uint64(freq))
for i := range timers {
tb := &timers[i]
if tb.gp != nil {
data = append(data, traceEvTimerGoroutine|0<<traceArgCountShift)
data = traceAppend(data, uint64(tb.gp.goid))
}
}
// 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)
}
ticks := uint64(cputicks()) / traceTickDiv
tickDiff := ticks - buf.lastTicks
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
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)*sys.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{}
}
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 - sys.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 = round(n, sys.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{pc + sys.PCQuantum})
traceEvent(traceEvGoCreate, 2, uint64(newg.goid), uint64(id))
}
func traceGoStart() {
_g_ := getg().m.curg
_p_ := _g_.m.p
_g_.traceseq++
if _g_ == _p_.ptr().gcBgMarkWorker.ptr() {
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, memstats.heap_live)
}
func traceNextGC() {
if memstats.next_gc == ^uint64(0) {
// Heap-based triggering is disabled.
traceEvent(traceEvNextGC, -1, 0)
} else {
traceEvent(traceEvNextGC, -1, memstats.next_gc)
}
}
// 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)
}