// Copyright 2009 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.

// Malloc profiling.
// Patterned after tcmalloc's algorithms; shorter code.

package runtime

import (
	
	
)

// NOTE(rsc): Everything here could use cas if contention became an issue.
var proflock mutex

// All memory allocations are local and do not escape outside of the profiler.
// The profiler is forbidden from referring to garbage-collected memory.

const (
	// profile types
	memProfile bucketType = 1 + iota
	blockProfile
	mutexProfile

	// size of bucket hash table
	buckHashSize = 179999

	// max depth of stack to record in bucket
	maxStack = 32
)

type bucketType int

// A bucket holds per-call-stack profiling information.
// The representation is a bit sleazy, inherited from C.
// This struct defines the bucket header. It is followed in
// memory by the stack words and then the actual record
// data, either a memRecord or a blockRecord.
//
// Per-call-stack profiling information.
// Lookup by hashing call stack into a linked-list hash table.
//
// No heap pointers.
//
//go:notinheap
type bucket struct {
	next    *bucket
	allnext *bucket
	typ     bucketType // memBucket or blockBucket (includes mutexProfile)
	hash    uintptr
	size    uintptr
	nstk    uintptr
}

// A memRecord is the bucket data for a bucket of type memProfile,
// part of the memory profile.
type memRecord struct {
	// The following complex 3-stage scheme of stats accumulation
	// is required to obtain a consistent picture of mallocs and frees
	// for some point in time.
	// The problem is that mallocs come in real time, while frees
	// come only after a GC during concurrent sweeping. So if we would
	// naively count them, we would get a skew toward mallocs.
	//
	// Hence, we delay information to get consistent snapshots as
	// of mark termination. Allocations count toward the next mark
	// termination's snapshot, while sweep frees count toward the
	// previous mark termination's snapshot:
	//
	//              MT          MT          MT          MT
	//             .·|         .·|         .·|         .·|
	//          .·˙  |      .·˙  |      .·˙  |      .·˙  |
	//       .·˙     |   .·˙     |   .·˙     |   .·˙     |
	//    .·˙        |.·˙        |.·˙        |.·˙        |
	//
	//       alloc → ▲ ← free
	//               ┠┅┅┅┅┅┅┅┅┅┅┅P
	//       C+2     →    C+1    →  C
	//
	//                   alloc → ▲ ← free
	//                           ┠┅┅┅┅┅┅┅┅┅┅┅P
	//                   C+2     →    C+1    →  C
	//
	// Since we can't publish a consistent snapshot until all of
	// the sweep frees are accounted for, we wait until the next
	// mark termination ("MT" above) to publish the previous mark
	// termination's snapshot ("P" above). To do this, allocation
	// and free events are accounted to *future* heap profile
	// cycles ("C+n" above) and we only publish a cycle once all
	// of the events from that cycle must be done. Specifically:
	//
	// Mallocs are accounted to cycle C+2.
	// Explicit frees are accounted to cycle C+2.
	// GC frees (done during sweeping) are accounted to cycle C+1.
	//
	// After mark termination, we increment the global heap
	// profile cycle counter and accumulate the stats from cycle C
	// into the active profile.

	// active is the currently published profile. A profiling
	// cycle can be accumulated into active once its complete.
	active memRecordCycle

	// future records the profile events we're counting for cycles
	// that have not yet been published. This is ring buffer
	// indexed by the global heap profile cycle C and stores
	// cycles C, C+1, and C+2. Unlike active, these counts are
	// only for a single cycle; they are not cumulative across
	// cycles.
	//
	// We store cycle C here because there's a window between when
	// C becomes the active cycle and when we've flushed it to
	// active.
	future [3]memRecordCycle
}

// memRecordCycle
type memRecordCycle struct {
	allocs, frees           uintptr
	alloc_bytes, free_bytes uintptr
}

// add accumulates b into a. It does not zero b.
func ( *memRecordCycle) ( *memRecordCycle) {
	.allocs += .allocs
	.frees += .frees
	.alloc_bytes += .alloc_bytes
	.free_bytes += .free_bytes
}

// A blockRecord is the bucket data for a bucket of type blockProfile,
// which is used in blocking and mutex profiles.
type blockRecord struct {
	count  float64
	cycles int64
}

var (
	mbuckets  *bucket // memory profile buckets
	bbuckets  *bucket // blocking profile buckets
	xbuckets  *bucket // mutex profile buckets
	buckhash  *[179999]*bucket
	bucketmem uintptr

	mProf struct {
		// All fields in mProf are protected by proflock.

		// cycle is the global heap profile cycle. This wraps
		// at mProfCycleWrap.
		cycle uint32
		// flushed indicates that future[cycle] in all buckets
		// has been flushed to the active profile.
		flushed bool
	}
)

const mProfCycleWrap = uint32(len(memRecord{}.future)) * (2 << 24)

// newBucket allocates a bucket with the given type and number of stack entries.
func newBucket( bucketType,  int) *bucket {
	 := unsafe.Sizeof(bucket{}) + uintptr()*unsafe.Sizeof(uintptr(0))
	switch  {
	default:
		throw("invalid profile bucket type")
	case memProfile:
		 += unsafe.Sizeof(memRecord{})
	case blockProfile, mutexProfile:
		 += unsafe.Sizeof(blockRecord{})
	}

	 := (*bucket)(persistentalloc(, 0, &memstats.buckhash_sys))
	bucketmem += 
	.typ = 
	.nstk = uintptr()
	return 
}

// stk returns the slice in b holding the stack.
func ( *bucket) () []uintptr {
	 := (*[maxStack]uintptr)(add(unsafe.Pointer(), unsafe.Sizeof(*)))
	return [:.nstk:.nstk]
}

// mp returns the memRecord associated with the memProfile bucket b.
func ( *bucket) () *memRecord {
	if .typ != memProfile {
		throw("bad use of bucket.mp")
	}
	 := add(unsafe.Pointer(), unsafe.Sizeof(*)+.nstk*unsafe.Sizeof(uintptr(0)))
	return (*memRecord)()
}

// bp returns the blockRecord associated with the blockProfile bucket b.
func ( *bucket) () *blockRecord {
	if .typ != blockProfile && .typ != mutexProfile {
		throw("bad use of bucket.bp")
	}
	 := add(unsafe.Pointer(), unsafe.Sizeof(*)+.nstk*unsafe.Sizeof(uintptr(0)))
	return (*blockRecord)()
}

// Return the bucket for stk[0:nstk], allocating new bucket if needed.
func stkbucket( bucketType,  uintptr,  []uintptr,  bool) *bucket {
	if buckhash == nil {
		buckhash = (*[buckHashSize]*bucket)(sysAlloc(unsafe.Sizeof(*buckhash), &memstats.buckhash_sys))
		if buckhash == nil {
			throw("runtime: cannot allocate memory")
		}
	}

	// Hash stack.
	var  uintptr
	for ,  := range  {
		 += 
		 +=  << 10
		 ^=  >> 6
	}
	// hash in size
	 += 
	 +=  << 10
	 ^=  >> 6
	// finalize
	 +=  << 3
	 ^=  >> 11

	 := int( % buckHashSize)
	for  := buckhash[];  != nil;  = .next {
		if .typ ==  && .hash ==  && .size ==  && eqslice(.stk(), ) {
			return 
		}
	}

	if ! {
		return nil
	}

	// Create new bucket.
	 := newBucket(, len())
	copy(.stk(), )
	.hash = 
	.size = 
	.next = buckhash[]
	buckhash[] = 
	if  == memProfile {
		.allnext = mbuckets
		mbuckets = 
	} else if  == mutexProfile {
		.allnext = xbuckets
		xbuckets = 
	} else {
		.allnext = bbuckets
		bbuckets = 
	}
	return 
}

func eqslice(,  []uintptr) bool {
	if len() != len() {
		return false
	}
	for ,  := range  {
		if  != [] {
			return false
		}
	}
	return true
}

// mProf_NextCycle publishes the next heap profile cycle and creates a
// fresh heap profile cycle. This operation is fast and can be done
// during STW. The caller must call mProf_Flush before calling
// mProf_NextCycle again.
//
// This is called by mark termination during STW so allocations and
// frees after the world is started again count towards a new heap
// profiling cycle.
func mProf_NextCycle() {
	lock(&proflock)
	// We explicitly wrap mProf.cycle rather than depending on
	// uint wraparound because the memRecord.future ring does not
	// itself wrap at a power of two.
	mProf.cycle = (mProf.cycle + 1) % mProfCycleWrap
	mProf.flushed = false
	unlock(&proflock)
}

// mProf_Flush flushes the events from the current heap profiling
// cycle into the active profile. After this it is safe to start a new
// heap profiling cycle with mProf_NextCycle.
//
// This is called by GC after mark termination starts the world. In
// contrast with mProf_NextCycle, this is somewhat expensive, but safe
// to do concurrently.
func mProf_Flush() {
	lock(&proflock)
	if !mProf.flushed {
		mProf_FlushLocked()
		mProf.flushed = true
	}
	unlock(&proflock)
}

func mProf_FlushLocked() {
	 := mProf.cycle
	for  := mbuckets;  != nil;  = .allnext {
		 := .mp()

		// Flush cycle C into the published profile and clear
		// it for reuse.
		 := &.future[%uint32(len(.future))]
		.active.add()
		* = memRecordCycle{}
	}
}

// mProf_PostSweep records that all sweep frees for this GC cycle have
// completed. This has the effect of publishing the heap profile
// snapshot as of the last mark termination without advancing the heap
// profile cycle.
func mProf_PostSweep() {
	lock(&proflock)
	// Flush cycle C+1 to the active profile so everything as of
	// the last mark termination becomes visible. *Don't* advance
	// the cycle, since we're still accumulating allocs in cycle
	// C+2, which have to become C+1 in the next mark termination
	// and so on.
	 := mProf.cycle
	for  := mbuckets;  != nil;  = .allnext {
		 := .mp()
		 := &.future[(+1)%uint32(len(.future))]
		.active.add()
		* = memRecordCycle{}
	}
	unlock(&proflock)
}

// Called by malloc to record a profiled block.
func mProf_Malloc( unsafe.Pointer,  uintptr) {
	var  [maxStack]uintptr
	 := callers(4, [:])
	lock(&proflock)
	 := stkbucket(memProfile, , [:], true)
	 := mProf.cycle
	 := .mp()
	 := &.future[(+2)%uint32(len(.future))]
	.allocs++
	.alloc_bytes += 
	unlock(&proflock)

	// Setprofilebucket locks a bunch of other mutexes, so we call it outside of proflock.
	// This reduces potential contention and chances of deadlocks.
	// Since the object must be alive during call to mProf_Malloc,
	// it's fine to do this non-atomically.
	systemstack(func() {
		setprofilebucket(, )
	})
}

// Called when freeing a profiled block.
func mProf_Free( *bucket,  uintptr) {
	lock(&proflock)
	 := mProf.cycle
	 := .mp()
	 := &.future[(+1)%uint32(len(.future))]
	.frees++
	.free_bytes += 
	unlock(&proflock)
}

var blockprofilerate uint64 // in CPU ticks

// SetBlockProfileRate controls the fraction of goroutine blocking events
// that are reported in the blocking profile. The profiler aims to sample
// an average of one blocking event per rate nanoseconds spent blocked.
//
// To include every blocking event in the profile, pass rate = 1.
// To turn off profiling entirely, pass rate <= 0.
func ( int) {
	var  int64
	if  <= 0 {
		 = 0 // disable profiling
	} else if  == 1 {
		 = 1 // profile everything
	} else {
		// convert ns to cycles, use float64 to prevent overflow during multiplication
		 = int64(float64() * float64(tickspersecond()) / (1000 * 1000 * 1000))
		if  == 0 {
			 = 1
		}
	}

	atomic.Store64(&blockprofilerate, uint64())
}

func blockevent( int64,  int) {
	if  <= 0 {
		 = 1
	}

	 := int64(atomic.Load64(&blockprofilerate))
	if blocksampled(, ) {
		saveblockevent(, , +1, blockProfile)
	}
}

// blocksampled returns true for all events where cycles >= rate. Shorter
// events have a cycles/rate random chance of returning true.
func blocksampled(,  int64) bool {
	if  <= 0 || ( >  && int64(fastrand())% > ) {
		return false
	}
	return true
}

func saveblockevent(,  int64,  int,  bucketType) {
	 := getg()
	var  int
	var  [maxStack]uintptr
	if .m.curg == nil || .m.curg ==  {
		 = callers(, [:])
	} else {
		 = gcallers(.m.curg, , [:])
	}
	lock(&proflock)
	 := stkbucket(, 0, [:], true)

	if  == blockProfile &&  <  {
		// Remove sampling bias, see discussion on http://golang.org/cl/299991.
		.bp().count += float64() / float64()
		.bp().cycles += 
	} else {
		.bp().count++
		.bp().cycles += 
	}
	unlock(&proflock)
}

var mutexprofilerate uint64 // fraction sampled

// SetMutexProfileFraction controls the fraction of mutex contention events
// that are reported in the mutex profile. On average 1/rate events are
// reported. The previous rate is returned.
//
// To turn off profiling entirely, pass rate 0.
// To just read the current rate, pass rate < 0.
// (For n>1 the details of sampling may change.)
func ( int) int {
	if  < 0 {
		return int(mutexprofilerate)
	}
	 := mutexprofilerate
	atomic.Store64(&mutexprofilerate, uint64())
	return int()
}

//go:linkname mutexevent sync.event
func mutexevent( int64,  int) {
	if  < 0 {
		 = 0
	}
	 := int64(atomic.Load64(&mutexprofilerate))
	// TODO(pjw): measure impact of always calling fastrand vs using something
	// like malloc.go:nextSample()
	if  > 0 && int64(fastrand())% == 0 {
		saveblockevent(, , +1, mutexProfile)
	}
}

// Go interface to profile data.

// A StackRecord describes a single execution stack.
type StackRecord struct {
	Stack0 [32]uintptr // stack trace for this record; ends at first 0 entry
}

// Stack returns the stack trace associated with the record,
// a prefix of r.Stack0.
func ( *StackRecord) () []uintptr {
	for ,  := range .Stack0 {
		if  == 0 {
			return .Stack0[0:]
		}
	}
	return .Stack0[0:]
}

// MemProfileRate controls the fraction of memory allocations
// that are recorded and reported in the memory profile.
// The profiler aims to sample an average of
// one allocation per MemProfileRate bytes allocated.
//
// To include every allocated block in the profile, set MemProfileRate to 1.
// To turn off profiling entirely, set MemProfileRate to 0.
//
// The tools that process the memory profiles assume that the
// profile rate is constant across the lifetime of the program
// and equal to the current value. Programs that change the
// memory profiling rate should do so just once, as early as
// possible in the execution of the program (for example,
// at the beginning of main).
var MemProfileRate int = defaultMemProfileRate(512 * 1024)

// defaultMemProfileRate returns 0 if disableMemoryProfiling is set.
// It exists primarily for the godoc rendering of MemProfileRate
// above.
func defaultMemProfileRate( int) int {
	if disableMemoryProfiling {
		return 0
	}
	return 
}

// disableMemoryProfiling is set by the linker if runtime.MemProfile
// is not used and the link type guarantees nobody else could use it
// elsewhere.
var disableMemoryProfiling bool

// A MemProfileRecord describes the live objects allocated
// by a particular call sequence (stack trace).
type MemProfileRecord struct {
	AllocBytes, FreeBytes     int64       // number of bytes allocated, freed
	AllocObjects, FreeObjects int64       // number of objects allocated, freed
	Stack0                    [32]uintptr // stack trace for this record; ends at first 0 entry
}

// InUseBytes returns the number of bytes in use (AllocBytes - FreeBytes).
func ( *MemProfileRecord) () int64 { return .AllocBytes - .FreeBytes }

// InUseObjects returns the number of objects in use (AllocObjects - FreeObjects).
func ( *MemProfileRecord) () int64 {
	return .AllocObjects - .FreeObjects
}

// Stack returns the stack trace associated with the record,
// a prefix of r.Stack0.
func ( *MemProfileRecord) () []uintptr {
	for ,  := range .Stack0 {
		if  == 0 {
			return .Stack0[0:]
		}
	}
	return .Stack0[0:]
}

// MemProfile returns a profile of memory allocated and freed per allocation
// site.
//
// MemProfile returns n, the number of records in the current memory profile.
// If len(p) >= n, MemProfile copies the profile into p and returns n, true.
// If len(p) < n, MemProfile does not change p and returns n, false.
//
// If inuseZero is true, the profile includes allocation records
// where r.AllocBytes > 0 but r.AllocBytes == r.FreeBytes.
// These are sites where memory was allocated, but it has all
// been released back to the runtime.
//
// The returned profile may be up to two garbage collection cycles old.
// This is to avoid skewing the profile toward allocations; because
// allocations happen in real time but frees are delayed until the garbage
// collector performs sweeping, the profile only accounts for allocations
// that have had a chance to be freed by the garbage collector.
//
// Most clients should use the runtime/pprof package or
// the testing package's -test.memprofile flag instead
// of calling MemProfile directly.
func ( []MemProfileRecord,  bool) ( int,  bool) {
	lock(&proflock)
	// If we're between mProf_NextCycle and mProf_Flush, take care
	// of flushing to the active profile so we only have to look
	// at the active profile below.
	mProf_FlushLocked()
	 := true
	for  := mbuckets;  != nil;  = .allnext {
		 := .mp()
		if  || .active.alloc_bytes != .active.free_bytes {
			++
		}
		if .active.allocs != 0 || .active.frees != 0 {
			 = false
		}
	}
	if  {
		// Absolutely no data, suggesting that a garbage collection
		// has not yet happened. In order to allow profiling when
		// garbage collection is disabled from the beginning of execution,
		// accumulate all of the cycles, and recount buckets.
		 = 0
		for  := mbuckets;  != nil;  = .allnext {
			 := .mp()
			for  := range .future {
				.active.add(&.future[])
				.future[] = memRecordCycle{}
			}
			if  || .active.alloc_bytes != .active.free_bytes {
				++
			}
		}
	}
	if  <= len() {
		 = true
		 := 0
		for  := mbuckets;  != nil;  = .allnext {
			 := .mp()
			if  || .active.alloc_bytes != .active.free_bytes {
				record(&[], )
				++
			}
		}
	}
	unlock(&proflock)
	return
}

// Write b's data to r.
func record( *MemProfileRecord,  *bucket) {
	 := .mp()
	.AllocBytes = int64(.active.alloc_bytes)
	.FreeBytes = int64(.active.free_bytes)
	.AllocObjects = int64(.active.allocs)
	.FreeObjects = int64(.active.frees)
	if raceenabled {
		racewriterangepc(unsafe.Pointer(&.Stack0[0]), unsafe.Sizeof(.Stack0), getcallerpc(), funcPC(MemProfile))
	}
	if msanenabled {
		msanwrite(unsafe.Pointer(&.Stack0[0]), unsafe.Sizeof(.Stack0))
	}
	copy(.Stack0[:], .stk())
	for  := int(.nstk);  < len(.Stack0); ++ {
		.Stack0[] = 0
	}
}

func iterate_memprof( func(*bucket, uintptr, *uintptr, uintptr, uintptr, uintptr)) {
	lock(&proflock)
	for  := mbuckets;  != nil;  = .allnext {
		 := .mp()
		(, .nstk, &.stk()[0], .size, .active.allocs, .active.frees)
	}
	unlock(&proflock)
}

// BlockProfileRecord describes blocking events originated
// at a particular call sequence (stack trace).
type BlockProfileRecord struct {
	Count  int64
	Cycles int64
	StackRecord
}

// BlockProfile returns n, the number of records in the current blocking profile.
// If len(p) >= n, BlockProfile copies the profile into p and returns n, true.
// If len(p) < n, BlockProfile does not change p and returns n, false.
//
// Most clients should use the runtime/pprof package or
// the testing package's -test.blockprofile flag instead
// of calling BlockProfile directly.
func ( []BlockProfileRecord) ( int,  bool) {
	lock(&proflock)
	for  := bbuckets;  != nil;  = .allnext {
		++
	}
	if  <= len() {
		 = true
		for  := bbuckets;  != nil;  = .allnext {
			 := .bp()
			 := &[0]
			.Count = int64(.count)
			// Prevent callers from having to worry about division by zero errors.
			// See discussion on http://golang.org/cl/299991.
			if .Count == 0 {
				.Count = 1
			}
			.Cycles = .cycles
			if raceenabled {
				racewriterangepc(unsafe.Pointer(&.Stack0[0]), unsafe.Sizeof(.Stack0), getcallerpc(), funcPC())
			}
			if msanenabled {
				msanwrite(unsafe.Pointer(&.Stack0[0]), unsafe.Sizeof(.Stack0))
			}
			 := copy(.Stack0[:], .stk())
			for ;  < len(.Stack0); ++ {
				.Stack0[] = 0
			}
			 = [1:]
		}
	}
	unlock(&proflock)
	return
}

// MutexProfile returns n, the number of records in the current mutex profile.
// If len(p) >= n, MutexProfile copies the profile into p and returns n, true.
// Otherwise, MutexProfile does not change p, and returns n, false.
//
// Most clients should use the runtime/pprof package
// instead of calling MutexProfile directly.
func ( []BlockProfileRecord) ( int,  bool) {
	lock(&proflock)
	for  := xbuckets;  != nil;  = .allnext {
		++
	}
	if  <= len() {
		 = true
		for  := xbuckets;  != nil;  = .allnext {
			 := .bp()
			 := &[0]
			.Count = int64(.count)
			.Cycles = .cycles
			 := copy(.Stack0[:], .stk())
			for ;  < len(.Stack0); ++ {
				.Stack0[] = 0
			}
			 = [1:]
		}
	}
	unlock(&proflock)
	return
}

// ThreadCreateProfile returns n, the number of records in the thread creation profile.
// If len(p) >= n, ThreadCreateProfile copies the profile into p and returns n, true.
// If len(p) < n, ThreadCreateProfile does not change p and returns n, false.
//
// Most clients should use the runtime/pprof package instead
// of calling ThreadCreateProfile directly.
func ( []StackRecord) ( int,  bool) {
	 := (*m)(atomic.Loadp(unsafe.Pointer(&allm)))
	for  := ;  != nil;  = .alllink {
		++
	}
	if  <= len() {
		 = true
		 := 0
		for  := ;  != nil;  = .alllink {
			[].Stack0 = .createstack
			++
		}
	}
	return
}

//go:linkname runtime_goroutineProfileWithLabels runtime/pprof.runtime_goroutineProfileWithLabels
func runtime_goroutineProfileWithLabels( []StackRecord,  []unsafe.Pointer) ( int,  bool) {
	return goroutineProfileWithLabels(, )
}

// labels may be nil. If labels is non-nil, it must have the same length as p.
func goroutineProfileWithLabels( []StackRecord,  []unsafe.Pointer) ( int,  bool) {
	if  != nil && len() != len() {
		 = nil
	}
	 := getg()

	 := func( *g) bool {
		// Checking isSystemGoroutine here makes GoroutineProfile
		// consistent with both NumGoroutine and Stack.
		return  !=  && readgstatus() != _Gdead && !isSystemGoroutine(, false)
	}

	stopTheWorld("profile")

	// World is stopped, no locking required.
	 = 1
	forEachGRace(func( *g) {
		if () {
			++
		}
	})

	if  <= len() {
		 = true
		,  := , 

		// Save current goroutine.
		 := getcallersp()
		 := getcallerpc()
		systemstack(func() {
			saveg(, , , &[0])
		})
		 = [1:]

		// If we have a place to put our goroutine labelmap, insert it there.
		if  != nil {
			[0] = .labels
			 = [1:]
		}

		// Save other goroutines.
		forEachGRace(func( *g) {
			if !() {
				return
			}

			if len() == 0 {
				// Should be impossible, but better to return a
				// truncated profile than to crash the entire process.
				return
			}
			saveg(^uintptr(0), ^uintptr(0), , &[0])
			if  != nil {
				[0] = .labels
				 = [1:]
			}
			 = [1:]
		})
	}

	startTheWorld()
	return , 
}

// GoroutineProfile returns n, the number of records in the active goroutine stack profile.
// If len(p) >= n, GoroutineProfile copies the profile into p and returns n, true.
// If len(p) < n, GoroutineProfile does not change p and returns n, false.
//
// Most clients should use the runtime/pprof package instead
// of calling GoroutineProfile directly.
func ( []StackRecord) ( int,  bool) {

	return goroutineProfileWithLabels(, nil)
}

func saveg(,  uintptr,  *g,  *StackRecord) {
	 := gentraceback(, , 0, , 0, &.Stack0[0], len(.Stack0), nil, nil, 0)
	if  < len(.Stack0) {
		.Stack0[] = 0
	}
}

// Stack formats a stack trace of the calling goroutine into buf
// and returns the number of bytes written to buf.
// If all is true, Stack formats stack traces of all other goroutines
// into buf after the trace for the current goroutine.
func ( []byte,  bool) int {
	if  {
		stopTheWorld("stack trace")
	}

	 := 0
	if len() > 0 {
		 := getg()
		 := getcallersp()
		 := getcallerpc()
		systemstack(func() {
			 := getg()
			// Force traceback=1 to override GOTRACEBACK setting,
			// so that Stack's results are consistent.
			// GOTRACEBACK is only about crash dumps.
			.m.traceback = 1
			.writebuf = [0:0:len()]
			goroutineheader()
			traceback(, , 0, )
			if  {
				tracebackothers()
			}
			.m.traceback = 0
			 = len(.writebuf)
			.writebuf = nil
		})
	}

	if  {
		startTheWorld()
	}
	return 
}

// Tracing of alloc/free/gc.

var tracelock mutex

func tracealloc( unsafe.Pointer,  uintptr,  *_type) {
	lock(&tracelock)
	 := getg()
	.m.traceback = 2
	if  == nil {
		print("tracealloc(", , ", ", hex(), ")\n")
	} else {
		print("tracealloc(", , ", ", hex(), ", ", .string(), ")\n")
	}
	if .m.curg == nil ||  == .m.curg {
		goroutineheader()
		 := getcallerpc()
		 := getcallersp()
		systemstack(func() {
			traceback(, , 0, )
		})
	} else {
		goroutineheader(.m.curg)
		traceback(^uintptr(0), ^uintptr(0), 0, .m.curg)
	}
	print("\n")
	.m.traceback = 0
	unlock(&tracelock)
}

func tracefree( unsafe.Pointer,  uintptr) {
	lock(&tracelock)
	 := getg()
	.m.traceback = 2
	print("tracefree(", , ", ", hex(), ")\n")
	goroutineheader()
	 := getcallerpc()
	 := getcallersp()
	systemstack(func() {
		traceback(, , 0, )
	})
	print("\n")
	.m.traceback = 0
	unlock(&tracelock)
}

func tracegc() {
	lock(&tracelock)
	 := getg()
	.m.traceback = 2
	print("tracegc()\n")
	// running on m->g0 stack; show all non-g0 goroutines
	tracebackothers()
	print("end tracegc\n")
	print("\n")
	.m.traceback = 0
	unlock(&tracelock)
}