runtime: change mutex profile to count every blocked goroutine

[gostls13.git] / src / runtime / mprof.go

// 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 (
        "internal/abi"
        "runtime/internal/atomic"
        "runtime/internal/sys"
        "unsafe"
)

// NOTE(rsc): Everything here could use cas if contention became an issue.
var (
        // profInsertLock protects changes to the start of all *bucket linked lists
        profInsertLock mutex
        // profBlockLock protects the contents of every blockRecord struct
        profBlockLock mutex
        // profMemActiveLock protects the active field of every memRecord struct
        profMemActiveLock mutex
        // profMemFutureLock is a set of locks that protect the respective elements
        // of the future array of every memRecord struct
        profMemFutureLock [len(memRecord{}.future)]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.
//
// None of the fields in this bucket header are modified after
// creation, including its next and allnext links.
//
// No heap pointers.
type bucket struct {
        _       sys.NotInHeap
        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 (a *memRecordCycle) add(b *memRecordCycle) {
        a.allocs += b.allocs
        a.frees += b.frees
        a.alloc_bytes += b.alloc_bytes
        a.free_bytes += b.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 atomic.UnsafePointer // *bucket, memory profile buckets
        bbuckets atomic.UnsafePointer // *bucket, blocking profile buckets
        xbuckets atomic.UnsafePointer // *bucket, mutex profile buckets
        buckhash atomic.UnsafePointer // *buckhashArray

        mProfCycle mProfCycleHolder
)

type buckhashArray [buckHashSize]atomic.UnsafePointer // *bucket

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

// mProfCycleHolder holds the global heap profile cycle number (wrapped at
// mProfCycleWrap, stored starting at bit 1), and a flag (stored at bit 0) to
// indicate whether future[cycle] in all buckets has been queued to flush into
// the active profile.
type mProfCycleHolder struct {
        value atomic.Uint32
}

// read returns the current cycle count.
func (c *mProfCycleHolder) read() (cycle uint32) {
        v := c.value.Load()
        cycle = v >> 1
        return cycle
}

// setFlushed sets the flushed flag. It returns the current cycle count and the
// previous value of the flushed flag.
func (c *mProfCycleHolder) setFlushed() (cycle uint32, alreadyFlushed bool) {
        for {
                prev := c.value.Load()
                cycle = prev >> 1
                alreadyFlushed = (prev & 0x1) != 0
                next := prev | 0x1
                if c.value.CompareAndSwap(prev, next) {
                        return cycle, alreadyFlushed
                }
        }
}

// increment increases the cycle count by one, wrapping the value at
// mProfCycleWrap. It clears the flushed flag.
func (c *mProfCycleHolder) increment() {
        // We explicitly wrap mProfCycle rather than depending on
        // uint wraparound because the memRecord.future ring does not
        // itself wrap at a power of two.
        for {
                prev := c.value.Load()
                cycle := prev >> 1
                cycle = (cycle + 1) % mProfCycleWrap
                next := cycle << 1
                if c.value.CompareAndSwap(prev, next) {
                        break
                }
        }
}

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

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

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

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

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

// Return the bucket for stk[0:nstk], allocating new bucket if needed.
func stkbucket(typ bucketType, size uintptr, stk []uintptr, alloc bool) *bucket {
        bh := (*buckhashArray)(buckhash.Load())
        if bh == nil {
                lock(&profInsertLock)
                // check again under the lock
                bh = (*buckhashArray)(buckhash.Load())
                if bh == nil {
                        bh = (*buckhashArray)(sysAlloc(unsafe.Sizeof(buckhashArray{}), &memstats.buckhash_sys))
                        if bh == nil {
                                throw("runtime: cannot allocate memory")
                        }
                        buckhash.StoreNoWB(unsafe.Pointer(bh))
                }
                unlock(&profInsertLock)
        }

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

        i := int(h % buckHashSize)
        // first check optimistically, without the lock
        for b := (*bucket)(bh[i].Load()); b != nil; b = b.next {
                if b.typ == typ && b.hash == h && b.size == size && eqslice(b.stk(), stk) {
                        return b
                }
        }

        if !alloc {
                return nil
        }

        lock(&profInsertLock)
        // check again under the insertion lock
        for b := (*bucket)(bh[i].Load()); b != nil; b = b.next {
                if b.typ == typ && b.hash == h && b.size == size && eqslice(b.stk(), stk) {
                        unlock(&profInsertLock)
                        return b
                }
        }

        // Create new bucket.
        b := newBucket(typ, len(stk))
        copy(b.stk(), stk)
        b.hash = h
        b.size = size

        var allnext *atomic.UnsafePointer
        if typ == memProfile {
                allnext = &mbuckets
        } else if typ == mutexProfile {
                allnext = &xbuckets
        } else {
                allnext = &bbuckets
        }

        b.next = (*bucket)(bh[i].Load())
        b.allnext = (*bucket)(allnext.Load())

        bh[i].StoreNoWB(unsafe.Pointer(b))
        allnext.StoreNoWB(unsafe.Pointer(b))

        unlock(&profInsertLock)
        return b
}

func eqslice(x, y []uintptr) bool {
        if len(x) != len(y) {
                return false
        }
        for i, xi := range x {
                if xi != y[i] {
                        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() {
        mProfCycle.increment()
}

// 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() {
        cycle, alreadyFlushed := mProfCycle.setFlushed()
        if alreadyFlushed {
                return
        }

        index := cycle % uint32(len(memRecord{}.future))
        lock(&profMemActiveLock)
        lock(&profMemFutureLock[index])
        mProf_FlushLocked(index)
        unlock(&profMemFutureLock[index])
        unlock(&profMemActiveLock)
}

// mProf_FlushLocked flushes the events from the heap profiling cycle at index
// into the active profile. The caller must hold the lock for the active profile
// (profMemActiveLock) and for the profiling cycle at index
// (profMemFutureLock[index]).
func mProf_FlushLocked(index uint32) {
        assertLockHeld(&profMemActiveLock)
        assertLockHeld(&profMemFutureLock[index])
        head := (*bucket)(mbuckets.Load())
        for b := head; b != nil; b = b.allnext {
                mp := b.mp()

                // Flush cycle C into the published profile and clear
                // it for reuse.
                mpc := &mp.future[index]
                mp.active.add(mpc)
                *mpc = 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() {
        // 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.
        cycle := mProfCycle.read() + 1

        index := cycle % uint32(len(memRecord{}.future))
        lock(&profMemActiveLock)
        lock(&profMemFutureLock[index])
        mProf_FlushLocked(index)
        unlock(&profMemFutureLock[index])
        unlock(&profMemActiveLock)
}

// Called by malloc to record a profiled block.
func mProf_Malloc(p unsafe.Pointer, size uintptr) {
        var stk [maxStack]uintptr
        nstk := callers(4, stk[:])

        index := (mProfCycle.read() + 2) % uint32(len(memRecord{}.future))

        b := stkbucket(memProfile, size, stk[:nstk], true)
        mp := b.mp()
        mpc := &mp.future[index]

        lock(&profMemFutureLock[index])
        mpc.allocs++
        mpc.alloc_bytes += size
        unlock(&profMemFutureLock[index])

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

// Called when freeing a profiled block.
func mProf_Free(b *bucket, size uintptr) {
        index := (mProfCycle.read() + 1) % uint32(len(memRecord{}.future))

        mp := b.mp()
        mpc := &mp.future[index]

        lock(&profMemFutureLock[index])
        mpc.frees++
        mpc.free_bytes += size
        unlock(&profMemFutureLock[index])
}

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 SetBlockProfileRate(rate int) {
        var r int64
        if rate <= 0 {
                r = 0 // disable profiling
        } else if rate == 1 {
                r = 1 // profile everything
        } else {
                // convert ns to cycles, use float64 to prevent overflow during multiplication
                r = int64(float64(rate) * float64(tickspersecond()) / (1000 * 1000 * 1000))
                if r == 0 {
                        r = 1
                }
        }

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

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

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

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

func saveblockevent(cycles, rate int64, skip int, which bucketType) {
        gp := getg()
        var nstk int
        var stk [maxStack]uintptr
        if gp.m.curg == nil || gp.m.curg == gp {
                nstk = callers(skip, stk[:])
        } else {
                nstk = gcallers(gp.m.curg, skip, stk[:])
        }
        b := stkbucket(which, 0, stk[:nstk], true)
        bp := b.bp()

        lock(&profBlockLock)
        // We want to up-scale the count and cycles according to the
        // probability that the event was sampled. For block profile events,
        // the sample probability is 1 if cycles >= rate, and cycles / rate
        // otherwise. For mutex profile events, the sample probability is 1 / rate.
        // We scale the events by 1 / (probability the event was sampled).
        if which == blockProfile && cycles < rate {
                // Remove sampling bias, see discussion on http://golang.org/cl/299991.
                bp.count += float64(rate) / float64(cycles)
                bp.cycles += rate
        } else if which == mutexProfile {
                bp.count += float64(rate)
                bp.cycles += rate * cycles
        } else {
                bp.count++
                bp.cycles += cycles
        }
        unlock(&profBlockLock)
}

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 SetMutexProfileFraction(rate int) int {
        if rate < 0 {
                return int(mutexprofilerate)
        }
        old := mutexprofilerate
        atomic.Store64(&mutexprofilerate, uint64(rate))
        return int(old)
}

//go:linkname mutexevent sync.event
func mutexevent(cycles int64, skip int) {
        if cycles < 0 {
                cycles = 0
        }
        rate := int64(atomic.Load64(&mutexprofilerate))
        if rate > 0 && int64(fastrand())%rate == 0 {
                saveblockevent(cycles, rate, skip+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 (r *StackRecord) Stack() []uintptr {
        for i, v := range r.Stack0 {
                if v == 0 {
                        return r.Stack0[0:i]
                }
        }
        return r.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 = 512 * 1024

// 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 (r *MemProfileRecord) InUseBytes() int64 { return r.AllocBytes - r.FreeBytes }

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

// Stack returns the stack trace associated with the record,
// a prefix of r.Stack0.
func (r *MemProfileRecord) Stack() []uintptr {
        for i, v := range r.Stack0 {
                if v == 0 {
                        return r.Stack0[0:i]
                }
        }
        return r.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 MemProfile(p []MemProfileRecord, inuseZero bool) (n int, ok bool) {
        cycle := mProfCycle.read()
        // 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.
        index := cycle % uint32(len(memRecord{}.future))
        lock(&profMemActiveLock)
        lock(&profMemFutureLock[index])
        mProf_FlushLocked(index)
        unlock(&profMemFutureLock[index])
        clear := true
        head := (*bucket)(mbuckets.Load())
        for b := head; b != nil; b = b.allnext {
                mp := b.mp()
                if inuseZero || mp.active.alloc_bytes != mp.active.free_bytes {
                        n++
                }
                if mp.active.allocs != 0 || mp.active.frees != 0 {
                        clear = false
                }
        }
        if clear {
                // 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.
                n = 0
                for b := head; b != nil; b = b.allnext {
                        mp := b.mp()
                        for c := range mp.future {
                                lock(&profMemFutureLock[c])
                                mp.active.add(&mp.future[c])
                                mp.future[c] = memRecordCycle{}
                                unlock(&profMemFutureLock[c])
                        }
                        if inuseZero || mp.active.alloc_bytes != mp.active.free_bytes {
                                n++
                        }
                }
        }
        if n <= len(p) {
                ok = true
                idx := 0
                for b := head; b != nil; b = b.allnext {
                        mp := b.mp()
                        if inuseZero || mp.active.alloc_bytes != mp.active.free_bytes {
                                record(&p[idx], b)
                                idx++
                        }
                }
        }
        unlock(&profMemActiveLock)
        return
}

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

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

// 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 BlockProfile(p []BlockProfileRecord) (n int, ok bool) {
        lock(&profBlockLock)
        head := (*bucket)(bbuckets.Load())
        for b := head; b != nil; b = b.allnext {
                n++
        }
        if n <= len(p) {
                ok = true
                for b := head; b != nil; b = b.allnext {
                        bp := b.bp()
                        r := &p[0]
                        r.Count = int64(bp.count)
                        // Prevent callers from having to worry about division by zero errors.
                        // See discussion on http://golang.org/cl/299991.
                        if r.Count == 0 {
                                r.Count = 1
                        }
                        r.Cycles = bp.cycles
                        if raceenabled {
                                racewriterangepc(unsafe.Pointer(&r.Stack0[0]), unsafe.Sizeof(r.Stack0), getcallerpc(), abi.FuncPCABIInternal(BlockProfile))
                        }
                        if msanenabled {
                                msanwrite(unsafe.Pointer(&r.Stack0[0]), unsafe.Sizeof(r.Stack0))
                        }
                        if asanenabled {
                                asanwrite(unsafe.Pointer(&r.Stack0[0]), unsafe.Sizeof(r.Stack0))
                        }
                        i := copy(r.Stack0[:], b.stk())
                        for ; i < len(r.Stack0); i++ {
                                r.Stack0[i] = 0
                        }
                        p = p[1:]
                }
        }
        unlock(&profBlockLock)
        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 MutexProfile(p []BlockProfileRecord) (n int, ok bool) {
        lock(&profBlockLock)
        head := (*bucket)(xbuckets.Load())
        for b := head; b != nil; b = b.allnext {
                n++
        }
        if n <= len(p) {
                ok = true
                for b := head; b != nil; b = b.allnext {
                        bp := b.bp()
                        r := &p[0]
                        r.Count = int64(bp.count)
                        r.Cycles = bp.cycles
                        i := copy(r.Stack0[:], b.stk())
                        for ; i < len(r.Stack0); i++ {
                                r.Stack0[i] = 0
                        }
                        p = p[1:]
                }
        }
        unlock(&profBlockLock)
        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 ThreadCreateProfile(p []StackRecord) (n int, ok bool) {
        first := (*m)(atomic.Loadp(unsafe.Pointer(&allm)))
        for mp := first; mp != nil; mp = mp.alllink {
                n++
        }
        if n <= len(p) {
                ok = true
                i := 0
                for mp := first; mp != nil; mp = mp.alllink {
                        p[i].Stack0 = mp.createstack
                        i++
                }
        }
        return
}

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

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

        return goroutineProfileWithLabelsConcurrent(p, labels)
}

var goroutineProfile = struct {
        sema    uint32
        active  bool
        offset  atomic.Int64
        records []StackRecord
        labels  []unsafe.Pointer
}{
        sema: 1,
}

// goroutineProfileState indicates the status of a goroutine's stack for the
// current in-progress goroutine profile. Goroutines' stacks are initially
// "Absent" from the profile, and end up "Satisfied" by the time the profile is
// complete. While a goroutine's stack is being captured, its
// goroutineProfileState will be "InProgress" and it will not be able to run
// until the capture completes and the state moves to "Satisfied".
//
// Some goroutines (the finalizer goroutine, which at various times can be
// either a "system" or a "user" goroutine, and the goroutine that is
// coordinating the profile, any goroutines created during the profile) move
// directly to the "Satisfied" state.
type goroutineProfileState uint32

const (
        goroutineProfileAbsent goroutineProfileState = iota
        goroutineProfileInProgress
        goroutineProfileSatisfied
)

type goroutineProfileStateHolder atomic.Uint32

func (p *goroutineProfileStateHolder) Load() goroutineProfileState {
        return goroutineProfileState((*atomic.Uint32)(p).Load())
}

func (p *goroutineProfileStateHolder) Store(value goroutineProfileState) {
        (*atomic.Uint32)(p).Store(uint32(value))
}

func (p *goroutineProfileStateHolder) CompareAndSwap(old, new goroutineProfileState) bool {
        return (*atomic.Uint32)(p).CompareAndSwap(uint32(old), uint32(new))
}

func goroutineProfileWithLabelsConcurrent(p []StackRecord, labels []unsafe.Pointer) (n int, ok bool) {
        semacquire(&goroutineProfile.sema)

        ourg := getg()

        stopTheWorld(stwGoroutineProfile)
        // Using gcount while the world is stopped should give us a consistent view
        // of the number of live goroutines, minus the number of goroutines that are
        // alive and permanently marked as "system". But to make this count agree
        // with what we'd get from isSystemGoroutine, we need special handling for
        // goroutines that can vary between user and system to ensure that the count
        // doesn't change during the collection. So, check the finalizer goroutine
        // in particular.
        n = int(gcount())
        if fingStatus.Load()&fingRunningFinalizer != 0 {
                n++
        }

        if n > len(p) {
                // There's not enough space in p to store the whole profile, so (per the
                // contract of runtime.GoroutineProfile) we're not allowed to write to p
                // at all and must return n, false.
                startTheWorld()
                semrelease(&goroutineProfile.sema)
                return n, false
        }

        // Save current goroutine.
        sp := getcallersp()
        pc := getcallerpc()
        systemstack(func() {
                saveg(pc, sp, ourg, &p[0])
        })
        ourg.goroutineProfiled.Store(goroutineProfileSatisfied)
        goroutineProfile.offset.Store(1)

        // Prepare for all other goroutines to enter the profile. Aside from ourg,
        // every goroutine struct in the allgs list has its goroutineProfiled field
        // cleared. Any goroutine created from this point on (while
        // goroutineProfile.active is set) will start with its goroutineProfiled
        // field set to goroutineProfileSatisfied.
        goroutineProfile.active = true
        goroutineProfile.records = p
        goroutineProfile.labels = labels
        // The finalizer goroutine needs special handling because it can vary over
        // time between being a user goroutine (eligible for this profile) and a
        // system goroutine (to be excluded). Pick one before restarting the world.
        if fing != nil {
                fing.goroutineProfiled.Store(goroutineProfileSatisfied)
                if readgstatus(fing) != _Gdead && !isSystemGoroutine(fing, false) {
                        doRecordGoroutineProfile(fing)
                }
        }
        startTheWorld()

        // Visit each goroutine that existed as of the startTheWorld call above.
        //
        // New goroutines may not be in this list, but we didn't want to know about
        // them anyway. If they do appear in this list (via reusing a dead goroutine
        // struct, or racing to launch between the world restarting and us getting
        // the list), they will already have their goroutineProfiled field set to
        // goroutineProfileSatisfied before their state transitions out of _Gdead.
        //
        // Any goroutine that the scheduler tries to execute concurrently with this
        // call will start by adding itself to the profile (before the act of
        // executing can cause any changes in its stack).
        forEachGRace(func(gp1 *g) {
                tryRecordGoroutineProfile(gp1, Gosched)
        })

        stopTheWorld(stwGoroutineProfileCleanup)
        endOffset := goroutineProfile.offset.Swap(0)
        goroutineProfile.active = false
        goroutineProfile.records = nil
        goroutineProfile.labels = nil
        startTheWorld()

        // Restore the invariant that every goroutine struct in allgs has its
        // goroutineProfiled field cleared.
        forEachGRace(func(gp1 *g) {
                gp1.goroutineProfiled.Store(goroutineProfileAbsent)
        })

        if raceenabled {
                raceacquire(unsafe.Pointer(&labelSync))
        }

        if n != int(endOffset) {
                // It's a big surprise that the number of goroutines changed while we
                // were collecting the profile. But probably better to return a
                // truncated profile than to crash the whole process.
                //
                // For instance, needm moves a goroutine out of the _Gdead state and so
                // might be able to change the goroutine count without interacting with
                // the scheduler. For code like that, the race windows are small and the
                // combination of features is uncommon, so it's hard to be (and remain)
                // sure we've caught them all.
        }

        semrelease(&goroutineProfile.sema)
        return n, true
}

// tryRecordGoroutineProfileWB asserts that write barriers are allowed and calls
// tryRecordGoroutineProfile.
//
//go:yeswritebarrierrec
func tryRecordGoroutineProfileWB(gp1 *g) {
        if getg().m.p.ptr() == nil {
                throw("no P available, write barriers are forbidden")
        }
        tryRecordGoroutineProfile(gp1, osyield)
}

// tryRecordGoroutineProfile ensures that gp1 has the appropriate representation
// in the current goroutine profile: either that it should not be profiled, or
// that a snapshot of its call stack and labels are now in the profile.
func tryRecordGoroutineProfile(gp1 *g, yield func()) {
        if readgstatus(gp1) == _Gdead {
                // Dead goroutines should not appear in the profile. Goroutines that
                // start while profile collection is active will get goroutineProfiled
                // set to goroutineProfileSatisfied before transitioning out of _Gdead,
                // so here we check _Gdead first.
                return
        }
        if isSystemGoroutine(gp1, true) {
                // System goroutines should not appear in the profile. (The finalizer
                // goroutine is marked as "already profiled".)
                return
        }

        for {
                prev := gp1.goroutineProfiled.Load()
                if prev == goroutineProfileSatisfied {
                        // This goroutine is already in the profile (or is new since the
                        // start of collection, so shouldn't appear in the profile).
                        break
                }
                if prev == goroutineProfileInProgress {
                        // Something else is adding gp1 to the goroutine profile right now.
                        // Give that a moment to finish.
                        yield()
                        continue
                }

                // While we have gp1.goroutineProfiled set to
                // goroutineProfileInProgress, gp1 may appear _Grunnable but will not
                // actually be able to run. Disable preemption for ourselves, to make
                // sure we finish profiling gp1 right away instead of leaving it stuck
                // in this limbo.
                mp := acquirem()
                if gp1.goroutineProfiled.CompareAndSwap(goroutineProfileAbsent, goroutineProfileInProgress) {
                        doRecordGoroutineProfile(gp1)
                        gp1.goroutineProfiled.Store(goroutineProfileSatisfied)
                }
                releasem(mp)
        }
}

// doRecordGoroutineProfile writes gp1's call stack and labels to an in-progress
// goroutine profile. Preemption is disabled.
//
// This may be called via tryRecordGoroutineProfile in two ways: by the
// goroutine that is coordinating the goroutine profile (running on its own
// stack), or from the scheduler in preparation to execute gp1 (running on the
// system stack).
func doRecordGoroutineProfile(gp1 *g) {
        if readgstatus(gp1) == _Grunning {
                print("doRecordGoroutineProfile gp1=", gp1.goid, "\n")
                throw("cannot read stack of running goroutine")
        }

        offset := int(goroutineProfile.offset.Add(1)) - 1

        if offset >= len(goroutineProfile.records) {
                // Should be impossible, but better to return a truncated profile than
                // to crash the entire process at this point. Instead, deal with it in
                // goroutineProfileWithLabelsConcurrent where we have more context.
                return
        }

        // saveg calls gentraceback, which may call cgo traceback functions. When
        // called from the scheduler, this is on the system stack already so
        // traceback.go:cgoContextPCs will avoid calling back into the scheduler.
        //
        // When called from the goroutine coordinating the profile, we still have
        // set gp1.goroutineProfiled to goroutineProfileInProgress and so are still
        // preventing it from being truly _Grunnable. So we'll use the system stack
        // to avoid schedule delays.
        systemstack(func() { saveg(^uintptr(0), ^uintptr(0), gp1, &goroutineProfile.records[offset]) })

        if goroutineProfile.labels != nil {
                goroutineProfile.labels[offset] = gp1.labels
        }
}

func goroutineProfileWithLabelsSync(p []StackRecord, labels []unsafe.Pointer) (n int, ok bool) {
        gp := getg()

        isOK := func(gp1 *g) bool {
                // Checking isSystemGoroutine here makes GoroutineProfile
                // consistent with both NumGoroutine and Stack.
                return gp1 != gp && readgstatus(gp1) != _Gdead && !isSystemGoroutine(gp1, false)
        }

        stopTheWorld(stwGoroutineProfile)

        // World is stopped, no locking required.
        n = 1
        forEachGRace(func(gp1 *g) {
                if isOK(gp1) {
                        n++
                }
        })

        if n <= len(p) {
                ok = true
                r, lbl := p, labels

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

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

                // Save other goroutines.
                forEachGRace(func(gp1 *g) {
                        if !isOK(gp1) {
                                return
                        }

                        if len(r) == 0 {
                                // Should be impossible, but better to return a
                                // truncated profile than to crash the entire process.
                                return
                        }
                        // saveg calls gentraceback, which may call cgo traceback functions.
                        // The world is stopped, so it cannot use cgocall (which will be
                        // blocked at exitsyscall). Do it on the system stack so it won't
                        // call into the schedular (see traceback.go:cgoContextPCs).
                        systemstack(func() { saveg(^uintptr(0), ^uintptr(0), gp1, &r[0]) })
                        if labels != nil {
                                lbl[0] = gp1.labels
                                lbl = lbl[1:]
                        }
                        r = r[1:]
                })
        }

        if raceenabled {
                raceacquire(unsafe.Pointer(&labelSync))
        }

        startTheWorld()
        return n, ok
}

// 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 GoroutineProfile(p []StackRecord) (n int, ok bool) {

        return goroutineProfileWithLabels(p, nil)
}

func saveg(pc, sp uintptr, gp *g, r *StackRecord) {
        var u unwinder
        u.initAt(pc, sp, 0, gp, unwindSilentErrors)
        n := tracebackPCs(&u, 0, r.Stack0[:])
        if n < len(r.Stack0) {
                r.Stack0[n] = 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 Stack(buf []byte, all bool) int {
        if all {
                stopTheWorld(stwAllGoroutinesStack)
        }

        n := 0
        if len(buf) > 0 {
                gp := getg()
                sp := getcallersp()
                pc := getcallerpc()
                systemstack(func() {
                        g0 := getg()
                        // Force traceback=1 to override GOTRACEBACK setting,
                        // so that Stack's results are consistent.
                        // GOTRACEBACK is only about crash dumps.
                        g0.m.traceback = 1
                        g0.writebuf = buf[0:0:len(buf)]
                        goroutineheader(gp)
                        traceback(pc, sp, 0, gp)
                        if all {
                                tracebackothers(gp)
                        }
                        g0.m.traceback = 0
                        n = len(g0.writebuf)
                        g0.writebuf = nil
                })
        }

        if all {
                startTheWorld()
        }
        return n
}

// Tracing of alloc/free/gc.

var tracelock mutex

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

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

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