runtime: add execution tracing functionality
This is first patch of series of patches that implement tracing functionality.
Design doc:
https://docs.google.com/document/u/1/d/1FP5apqzBgr7ahCCgFO-yoVhk4YZrNIDNf9RybngBc14/pub
Full change:
https://codereview.appspot.com/146920043
Change-Id: I84588348bb05a6f6a102c230f3bca6380a3419fe
Reviewed-on: https://go-review.googlesource.com/1450
Reviewed-by: Russ Cox <rsc@golang.org>
diff --git a/src/runtime/runtime2.go b/src/runtime/runtime2.go
index 697ff69..f0f8c1a 100644
--- a/src/runtime/runtime2.go
+++ b/src/runtime/runtime2.go
@@ -213,6 +213,7 @@
sigcode1 uintptr
sigpc uintptr
gopc uintptr // pc of go statement that created this goroutine
+ startpc uintptr // pc of goroutine function
racectx uintptr
waiting *sudog // sudog structures this g is waiting on (that have a valid elem ptr)
}
@@ -324,6 +325,8 @@
gfree *g
gfreecnt int32
+ tracebuf *traceBuf
+
pad [64]byte
}
diff --git a/src/runtime/trace.go b/src/runtime/trace.go
new file mode 100644
index 0000000..17d0298
--- /dev/null
+++ b/src/runtime/trace.go
@@ -0,0 +1,790 @@
+// 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 http://golang.org/s/go15trace for more info.
+
+package runtime
+
+import "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 PCs]
+ traceEvGomaxprocs = 4 // current value of GOMAXPROCS [timestamp, GOMAXPROCS, stack id]
+ traceEvProcStart = 5 // start of P [timestamp]
+ traceEvProcStop = 6 // stop of P [timestamp]
+ traceEvGCStart = 7 // GC start [timestamp, stack id]
+ traceEvGCDone = 8 // GC done [timestamp]
+ traceEvGCScanStart = 9 // GC scan start [timestamp]
+ traceEvGCScanDone = 10 // GC scan done [timestamp]
+ traceEvGCSweepStart = 11 // GC sweep start [timestamp, stack id]
+ traceEvGCSweepDone = 12 // GC sweep done [timestamp]
+ traceEvGoCreate = 13 // goroutine creation [timestamp, new goroutine id, start PC, stack id]
+ traceEvGoStart = 14 // goroutine starts running [timestamp, goroutine id]
+ 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, 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]
+ traceEvGoSysBlock = 30 // syscall blocks [timestamp, stack]
+ traceEvGoWaiting = 31 // denotes that goroutine is blocked when tracing starts [goroutine id]
+ traceEvGoInSyscall = 32 // denotes that goroutine is in syscall when tracing starts [goroutine id]
+ traceEvHeapAlloc = 33 // memstats.heap_alloc change [timestamp, heap_alloc]
+ traceEvNextGC = 34 // memstats.next_gc change [timestamp, next_gc]
+ traceEvTimerGoroutine = 35 // denotes timer goroutine [timer goroutine id]
+ traceEvCount = 36
+)
+
+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 is somewhat arbitrary (one tick is ~20ns on a 3GHz machine).
+ traceTickDiv = 64
+ // 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
+)
+
+// 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
+ 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
+ reading *traceBuf // buffer currently handed off to user
+ empty *traceBuf // stack of empty buffers
+ fullHead *traceBuf // queue of full buffers
+ fullTail *traceBuf
+ reader *g // goroutine that called ReadTrace, or nil
+ stackTab traceStackTable // maps stack traces to unique ids
+
+ bufLock mutex // protects buf
+ buf *traceBuf // global trace buffer, used when running without a p
+}
+
+// traceBufHeader is per-P tracing buffer.
+type traceBufHeader struct {
+ link *traceBuf // in trace.empty/full
+ lastTicks uint64 // when we wrote the last event
+ buf []byte // trace data, always points to traceBuf.arr
+ stk [traceStackSize]uintptr // scratch buffer for traceback
+}
+
+// traceBuf is per-P tracing buffer.
+type traceBuf struct {
+ traceBufHeader
+ arr [64<<10 - unsafe.Sizeof(traceBufHeader{})]byte // underlying buffer for traceBufHeader.buf
+}
+
+// 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/pprof 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.
+ semacquire(&worldsema, false)
+ _g_ := getg()
+ _g_.m.gcing = 1
+ systemstack(stoptheworld)
+
+ // 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)
+ _g_.m.gcing = 0
+ semrelease(&worldsema)
+ systemstack(starttheworld)
+ return errorString("tracing is already enabled")
+ }
+
+ trace.ticksStart = cputicks()
+ trace.timeStart = nanotime()
+ trace.enabled = true
+ trace.headerWritten = false
+ trace.footerWritten = false
+
+ for _, gp := range allgs {
+ status := readgstatus(gp)
+ if status != _Gdead {
+ traceGoCreate(gp, gp.startpc)
+ }
+ if status == _Gwaiting {
+ traceEvent(traceEvGoWaiting, false, uint64(gp.goid))
+ }
+ if status == _Gsyscall {
+ traceEvent(traceEvGoInSyscall, false, uint64(gp.goid))
+ }
+ }
+ traceProcStart()
+ traceGoStart()
+
+ unlock(&trace.bufLock)
+
+ _g_.m.gcing = 0
+ semrelease(&worldsema)
+ systemstack(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.
+ semacquire(&worldsema, false)
+ _g_ := getg()
+ _g_.m.gcing = 1
+ systemstack(stoptheworld)
+
+ // See the comment in StartTrace.
+ lock(&trace.bufLock)
+
+ if !trace.enabled {
+ unlock(&trace.bufLock)
+ _g_.m.gcing = 0
+ semrelease(&worldsema)
+ systemstack(starttheworld)
+ return
+ }
+
+ traceGoSched()
+ traceGoStart()
+
+ for _, p := range &allp {
+ if p == nil {
+ break
+ }
+ buf := p.tracebuf
+ if buf != nil {
+ traceFullQueue(buf)
+ p.tracebuf = nil
+ }
+ }
+ if trace.buf != nil && len(trace.buf.buf) != 0 {
+ buf := trace.buf
+ trace.buf = nil
+ traceFullQueue(buf)
+ }
+
+ trace.ticksEnd = cputicks()
+ trace.timeEnd = nanotime()
+ trace.enabled = false
+ trace.shutdown = true
+ trace.stackTab.dump()
+
+ unlock(&trace.bufLock)
+
+ _g_.m.gcing = 0
+ semrelease(&worldsema)
+ systemstack(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, false)
+
+ // The lock protects us from races with StartTrace/StopTrace because they do stop-the-world.
+ lock(&trace.lock)
+ for _, p := range &allp {
+ if p == nil {
+ break
+ }
+ if p.tracebuf != nil {
+ throw("trace: non-empty trace buffer in proc")
+ }
+ }
+ if trace.buf != nil {
+ throw("trace: non-empty global trace buffer")
+ }
+ if trace.fullHead != nil || trace.fullTail != nil {
+ throw("trace: non-empty full trace buffer")
+ }
+ if trace.reading != nil || trace.reader != nil {
+ throw("trace: reading after shutdown")
+ }
+ for trace.empty != nil {
+ buf := trace.empty
+ trace.empty = buf.link
+ sysFree(unsafe.Pointer(buf), unsafe.Sizeof(*buf), &memstats.other_sys)
+ }
+ 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 != nil {
+ // 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 != nil {
+ buf.link = trace.empty
+ trace.empty = buf
+ trace.reading = nil
+ }
+ // Write trace header.
+ if !trace.headerWritten {
+ trace.headerWritten = true
+ trace.lockOwner = nil
+ unlock(&trace.lock)
+ return []byte("gotrace\x00")
+ }
+ // Wait for new data.
+ if trace.fullHead == nil && !trace.shutdown {
+ trace.reader = getg()
+ goparkunlock(&trace.lock, "trace reader (blocked)" /*, traceEvGoBlock*/)
+ lock(&trace.lock)
+ }
+ // Write a buffer.
+ if trace.fullHead != nil {
+ buf := traceFullDequeue()
+ trace.reading = buf
+ trace.lockOwner = nil
+ unlock(&trace.lock)
+ return buf.buf
+ }
+ // 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))
+ if timers.gp != nil {
+ data = append(data, traceEvTimerGoroutine|0<<traceArgCountShift)
+ data = traceAppend(data, uint64(timers.gp.goid))
+ }
+ return data
+ }
+ // Done.
+ if trace.shutdown {
+ trace.lockOwner = nil
+ unlock(&trace.lock)
+ // 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 == nil || (trace.fullHead == nil && !trace.shutdown) {
+ return nil
+ }
+ lock(&trace.lock)
+ if trace.reader == nil || (trace.fullHead == nil && !trace.shutdown) {
+ unlock(&trace.lock)
+ return nil
+ }
+ gp := trace.reader
+ trace.reader = nil
+ unlock(&trace.lock)
+ return gp
+}
+
+// traceProcFree frees trace buffer associated with pp.
+func traceProcFree(pp *p) {
+ buf := pp.tracebuf
+ pp.tracebuf = nil
+ if buf == nil {
+ return
+ }
+ lock(&trace.lock)
+ traceFullQueue(buf)
+ unlock(&trace.lock)
+}
+
+// traceFullQueue queues buf into queue of full buffers.
+func traceFullQueue(buf *traceBuf) {
+ buf.link = nil
+ if trace.fullHead == nil {
+ trace.fullHead = buf
+ } else {
+ trace.fullTail.link = buf
+ }
+ trace.fullTail = buf
+}
+
+// traceFullDequeue dequeues from queue of full buffers.
+func traceFullDequeue() *traceBuf {
+ buf := trace.fullHead
+ if buf == nil {
+ return nil
+ }
+ trace.fullHead = buf.link
+ if trace.fullHead == nil {
+ trace.fullTail = nil
+ }
+ buf.link = nil
+ return buf
+}
+
+// traceEvent writes a single event to trace buffer, flushing the buffer if necessary.
+// ev is event type.
+// If stack, write current stack id as the last argument.
+func traceEvent(ev byte, stack bool, 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.
+ if !trace.enabled {
+ traceReleaseBuffer(pid)
+ return
+ }
+ buf := *bufp
+ const maxSize = 2 + 4*traceBytesPerNumber // event type, length, timestamp, stack id and two add params
+ if buf == nil || cap(buf.buf)-len(buf.buf) < maxSize {
+ buf = traceFlush(buf)
+ *bufp = buf
+ }
+
+ ticks := uint64(cputicks()) / traceTickDiv
+ tickDiff := ticks - buf.lastTicks
+ if len(buf.buf) == 0 {
+ data := buf.buf
+ data = append(data, traceEvBatch|1<<traceArgCountShift)
+ data = traceAppend(data, uint64(pid))
+ data = traceAppend(data, ticks)
+ buf.buf = data
+ tickDiff = 0
+ }
+ buf.lastTicks = ticks
+ narg := byte(len(args))
+ if stack {
+ 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
+ }
+ data := buf.buf
+ data = append(data, ev|narg<<traceArgCountShift)
+ var lenp *byte
+ if narg == 3 {
+ // Reserve the byte for length assuming that length < 128.
+ data = append(data, 0)
+ lenp = &data[len(data)-1]
+ }
+ data = traceAppend(data, tickDiff)
+ for _, a := range args {
+ data = traceAppend(data, a)
+ }
+ if stack {
+ _g_ := getg()
+ gp := mp.curg
+ if gp == nil && ev == traceEvGoSysBlock {
+ gp = _g_
+ }
+ var nstk int
+ if gp == _g_ {
+ nstk = callers(1, &buf.stk[0], len(buf.stk))
+ } else if gp != nil {
+ nstk = gcallers(mp.curg, 1, &buf.stk[0], len(buf.stk))
+ }
+ id := trace.stackTab.put(buf.stk[:nstk])
+ data = traceAppend(data, uint64(id))
+ }
+ evSize := len(data) - len(buf.buf)
+ if evSize > maxSize {
+ throw("invalid length of trace event")
+ }
+ if lenp != nil {
+ // Fill in actual length.
+ *lenp = byte(evSize - 2)
+ }
+ buf.buf = data
+ traceReleaseBuffer(pid)
+}
+
+// traceAcquireBuffer returns trace buffer to use and, if necessary, locks it.
+func traceAcquireBuffer() (mp *m, pid int32, bufp **traceBuf) {
+ mp = acquirem()
+ if p := mp.p; 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 *traceBuf) *traceBuf {
+ owner := trace.lockOwner
+ dolock := owner == nil || owner != getg().m.curg
+ if dolock {
+ lock(&trace.lock)
+ }
+ if buf != nil {
+ if &buf.buf[0] != &buf.arr[0] {
+ throw("trace buffer overflow")
+ }
+ traceFullQueue(buf)
+ }
+ if trace.empty != nil {
+ buf = trace.empty
+ trace.empty = buf.link
+ } else {
+ buf = (*traceBuf)(sysAlloc(unsafe.Sizeof(traceBuf{}), &memstats.other_sys))
+ if buf == nil {
+ throw("trace: out of memory")
+ }
+ }
+ buf.link = nil
+ buf.buf = buf.arr[:0]
+ buf.lastTicks = 0
+ if dolock {
+ unlock(&trace.lock)
+ }
+ return buf
+}
+
+// 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
+}
+
+// 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]*traceStack
+}
+
+// traceStack is a single stack in traceStackTable.
+type traceStack struct {
+ link *traceStack
+ hash uintptr
+ id uint32
+ n int
+ stk [0]uintptr // real type [n]uintptr
+}
+
+// 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]), uintptr(len(pcs))*unsafe.Sizeof(pcs[0]), 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]; stk != nil; stk = stk.link {
+ 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)*ptrSize))
+}
+
+// dump writes all previously cached stacks to trace buffers,
+// releases all memory and resets state.
+func (tab *traceStackTable) dump() {
+ var tmp [(2 + traceStackSize) * traceBytesPerNumber]byte
+ buf := traceFlush(nil)
+ for _, stk := range tab.tab {
+ for ; stk != nil; stk = stk.link {
+ maxSize := 1 + (3+stk.n)*traceBytesPerNumber
+ if cap(buf.buf)-len(buf.buf) < maxSize {
+ buf = traceFlush(buf)
+ }
+ // Form the event in the temp buffer, we need to know the actual length.
+ tmpbuf := tmp[:0]
+ tmpbuf = traceAppend(tmpbuf, uint64(stk.id))
+ tmpbuf = traceAppend(tmpbuf, uint64(stk.n))
+ for _, pc := range stk.stack() {
+ tmpbuf = traceAppend(tmpbuf, uint64(pc))
+ }
+ // Now copy to the buffer.
+ data := buf.buf
+ data = append(data, traceEvStack|3<<traceArgCountShift)
+ data = traceAppend(data, uint64(len(tmpbuf)))
+ data = append(data, tmpbuf...)
+ buf.buf = data
+ }
+ }
+
+ lock(&trace.lock)
+ traceFullQueue(buf)
+ unlock(&trace.lock)
+
+ tab.mem.drop()
+ *tab = traceStackTable{}
+}
+
+// traceAlloc is a non-thread-safe region allocator.
+// It holds a linked list of traceAllocBlock.
+type traceAlloc struct {
+ head *traceAllocBlock
+ off uintptr
+}
+
+// traceAllocBlock is a block in traceAlloc.
+type traceAllocBlock struct {
+ next *traceAllocBlock
+ data [64<<10 - ptrSize]byte
+}
+
+// alloc allocates n-byte block.
+func (a *traceAlloc) alloc(n uintptr) unsafe.Pointer {
+ n = round(n, ptrSize)
+ if a.head == nil || a.off+n > uintptr(len(a.head.data)) {
+ if n > uintptr(len(a.head.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 = a.head
+ a.head = block
+ a.off = 0
+ }
+ p := &a.head.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 != nil {
+ block := a.head
+ a.head = block.next
+ sysFree(unsafe.Pointer(block), unsafe.Sizeof(traceAllocBlock{}), &memstats.other_sys)
+ }
+}
+
+// The following functions write specific events to trace.
+
+func traceGomaxprocs(procs int32) {
+ traceEvent(traceEvGomaxprocs, true, uint64(procs))
+}
+
+func traceProcStart() {
+ traceEvent(traceEvProcStart, false)
+}
+
+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 = pp
+ traceEvent(traceEvProcStop, false)
+ mp.p = oldp
+ releasem(mp)
+}
+
+func traceGCStart() {
+ traceEvent(traceEvGCStart, true)
+}
+
+func traceGCDone() {
+ traceEvent(traceEvGCDone, false)
+}
+
+func traceGCScanStart() {
+ traceEvent(traceEvGCScanStart, false)
+}
+
+func traceGCScanDone() {
+ traceEvent(traceEvGCScanDone, false)
+}
+
+func traceGCSweepStart() {
+ traceEvent(traceEvGCSweepStart, true)
+}
+
+func traceGCSweepDone() {
+ traceEvent(traceEvGCSweepDone, false)
+}
+
+func traceGoCreate(newg *g, pc uintptr) {
+ traceEvent(traceEvGoCreate, true, uint64(newg.goid), uint64(pc))
+}
+
+func traceGoStart() {
+ traceEvent(traceEvGoStart, false, uint64(getg().m.curg.goid))
+}
+
+func traceGoEnd() {
+ traceEvent(traceEvGoEnd, false)
+}
+
+func traceGoSched() {
+ traceEvent(traceEvGoSched, true)
+}
+
+func traceGoPreempt() {
+ traceEvent(traceEvGoPreempt, true)
+}
+
+func traceGoStop() {
+ traceEvent(traceEvGoStop, true)
+}
+
+func traceGoPark(traceEv byte, gp *g) {
+ traceEvent(traceEv, true)
+}
+
+func traceGoUnpark(gp *g) {
+ traceEvent(traceEvGoUnblock, true, uint64(gp.goid))
+}
+
+func traceGoSysCall() {
+ traceEvent(traceEvGoSysCall, true)
+}
+
+func traceGoSysExit() {
+ traceEvent(traceEvGoSysExit, false, uint64(getg().m.curg.goid))
+}
+
+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 = pp
+ traceEvent(traceEvGoSysBlock, true)
+ mp.p = oldp
+ releasem(mp)
+}
+
+func traceHeapAlloc() {
+ traceEvent(traceEvHeapAlloc, false, memstats.heap_alloc)
+}
+
+func traceNextGC() {
+ traceEvent(traceEvNextGC, false, memstats.next_gc)
+}
