Source file src/runtime/mprof.go

Documentation: runtime

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Malloc profiling.
     6  // Patterned after tcmalloc's algorithms; shorter code.
     7  
     8  package runtime
     9  
    10  import (
    11  	"internal/abi"
    12  	"runtime/internal/atomic"
    13  	"runtime/internal/sys"
    14  	"unsafe"
    15  )
    16  
    17  // NOTE(rsc): Everything here could use cas if contention became an issue.
    18  var (
    19  	// profInsertLock protects changes to the start of all *bucket linked lists
    20  	profInsertLock mutex
    21  	// profBlockLock protects the contents of every blockRecord struct
    22  	profBlockLock mutex
    23  	// profMemActiveLock protects the active field of every memRecord struct
    24  	profMemActiveLock mutex
    25  	// profMemFutureLock is a set of locks that protect the respective elements
    26  	// of the future array of every memRecord struct
    27  	profMemFutureLock [len(memRecord{}.future)]mutex
    28  )
    29  
    30  // All memory allocations are local and do not escape outside of the profiler.
    31  // The profiler is forbidden from referring to garbage-collected memory.
    32  
    33  const (
    34  	// profile types
    35  	memProfile bucketType = 1 + iota
    36  	blockProfile
    37  	mutexProfile
    38  
    39  	// size of bucket hash table
    40  	buckHashSize = 179999
    41  
    42  	// maxStack is the max depth of stack to record in bucket.
    43  	// Note that it's only used internally as a guard against
    44  	// wildly out-of-bounds slicing of the PCs that come after
    45  	// a bucket struct, and it could increase in the future.
    46  	maxStack = 32
    47  )
    48  
    49  type bucketType int
    50  
    51  // A bucket holds per-call-stack profiling information.
    52  // The representation is a bit sleazy, inherited from C.
    53  // This struct defines the bucket header. It is followed in
    54  // memory by the stack words and then the actual record
    55  // data, either a memRecord or a blockRecord.
    56  //
    57  // Per-call-stack profiling information.
    58  // Lookup by hashing call stack into a linked-list hash table.
    59  //
    60  // None of the fields in this bucket header are modified after
    61  // creation, including its next and allnext links.
    62  //
    63  // No heap pointers.
    64  type bucket struct {
    65  	_       sys.NotInHeap
    66  	next    *bucket
    67  	allnext *bucket
    68  	typ     bucketType // memBucket or blockBucket (includes mutexProfile)
    69  	hash    uintptr
    70  	size    uintptr
    71  	nstk    uintptr
    72  }
    73  
    74  // A memRecord is the bucket data for a bucket of type memProfile,
    75  // part of the memory profile.
    76  type memRecord struct {
    77  	// The following complex 3-stage scheme of stats accumulation
    78  	// is required to obtain a consistent picture of mallocs and frees
    79  	// for some point in time.
    80  	// The problem is that mallocs come in real time, while frees
    81  	// come only after a GC during concurrent sweeping. So if we would
    82  	// naively count them, we would get a skew toward mallocs.
    83  	//
    84  	// Hence, we delay information to get consistent snapshots as
    85  	// of mark termination. Allocations count toward the next mark
    86  	// termination's snapshot, while sweep frees count toward the
    87  	// previous mark termination's snapshot:
    88  	//
    89  	//              MT          MT          MT          MT
    90  	//             .·|         .·|         .·|         .·|
    91  	//          .·˙  |      .·˙  |      .·˙  |      .·˙  |
    92  	//       .·˙     |   .·˙     |   .·˙     |   .·˙     |
    93  	//    .·˙        |.·˙        |.·˙        |.·˙        |
    94  	//
    95  	//       alloc → ▲ ← free
    96  	//               ┠┅┅┅┅┅┅┅┅┅┅┅P
    97  	//       C+2     →    C+1    →  C
    98  	//
    99  	//                   alloc → ▲ ← free
   100  	//                           ┠┅┅┅┅┅┅┅┅┅┅┅P
   101  	//                   C+2     →    C+1    →  C
   102  	//
   103  	// Since we can't publish a consistent snapshot until all of
   104  	// the sweep frees are accounted for, we wait until the next
   105  	// mark termination ("MT" above) to publish the previous mark
   106  	// termination's snapshot ("P" above). To do this, allocation
   107  	// and free events are accounted to *future* heap profile
   108  	// cycles ("C+n" above) and we only publish a cycle once all
   109  	// of the events from that cycle must be done. Specifically:
   110  	//
   111  	// Mallocs are accounted to cycle C+2.
   112  	// Explicit frees are accounted to cycle C+2.
   113  	// GC frees (done during sweeping) are accounted to cycle C+1.
   114  	//
   115  	// After mark termination, we increment the global heap
   116  	// profile cycle counter and accumulate the stats from cycle C
   117  	// into the active profile.
   118  
   119  	// active is the currently published profile. A profiling
   120  	// cycle can be accumulated into active once its complete.
   121  	active memRecordCycle
   122  
   123  	// future records the profile events we're counting for cycles
   124  	// that have not yet been published. This is ring buffer
   125  	// indexed by the global heap profile cycle C and stores
   126  	// cycles C, C+1, and C+2. Unlike active, these counts are
   127  	// only for a single cycle; they are not cumulative across
   128  	// cycles.
   129  	//
   130  	// We store cycle C here because there's a window between when
   131  	// C becomes the active cycle and when we've flushed it to
   132  	// active.
   133  	future [3]memRecordCycle
   134  }
   135  
   136  // memRecordCycle
   137  type memRecordCycle struct {
   138  	allocs, frees           uintptr
   139  	alloc_bytes, free_bytes uintptr
   140  }
   141  
   142  // add accumulates b into a. It does not zero b.
   143  func (a *memRecordCycle) add(b *memRecordCycle) {
   144  	a.allocs += b.allocs
   145  	a.frees += b.frees
   146  	a.alloc_bytes += b.alloc_bytes
   147  	a.free_bytes += b.free_bytes
   148  }
   149  
   150  // A blockRecord is the bucket data for a bucket of type blockProfile,
   151  // which is used in blocking and mutex profiles.
   152  type blockRecord struct {
   153  	count  float64
   154  	cycles int64
   155  }
   156  
   157  var (
   158  	mbuckets atomic.UnsafePointer // *bucket, memory profile buckets
   159  	bbuckets atomic.UnsafePointer // *bucket, blocking profile buckets
   160  	xbuckets atomic.UnsafePointer // *bucket, mutex profile buckets
   161  	buckhash atomic.UnsafePointer // *buckhashArray
   162  
   163  	mProfCycle mProfCycleHolder
   164  )
   165  
   166  type buckhashArray [buckHashSize]atomic.UnsafePointer // *bucket
   167  
   168  const mProfCycleWrap = uint32(len(memRecord{}.future)) * (2 << 24)
   169  
   170  // mProfCycleHolder holds the global heap profile cycle number (wrapped at
   171  // mProfCycleWrap, stored starting at bit 1), and a flag (stored at bit 0) to
   172  // indicate whether future[cycle] in all buckets has been queued to flush into
   173  // the active profile.
   174  type mProfCycleHolder struct {
   175  	value atomic.Uint32
   176  }
   177  
   178  // read returns the current cycle count.
   179  func (c *mProfCycleHolder) read() (cycle uint32) {
   180  	v := c.value.Load()
   181  	cycle = v >> 1
   182  	return cycle
   183  }
   184  
   185  // setFlushed sets the flushed flag. It returns the current cycle count and the
   186  // previous value of the flushed flag.
   187  func (c *mProfCycleHolder) setFlushed() (cycle uint32, alreadyFlushed bool) {
   188  	for {
   189  		prev := c.value.Load()
   190  		cycle = prev >> 1
   191  		alreadyFlushed = (prev & 0x1) != 0
   192  		next := prev | 0x1
   193  		if c.value.CompareAndSwap(prev, next) {
   194  			return cycle, alreadyFlushed
   195  		}
   196  	}
   197  }
   198  
   199  // increment increases the cycle count by one, wrapping the value at
   200  // mProfCycleWrap. It clears the flushed flag.
   201  func (c *mProfCycleHolder) increment() {
   202  	// We explicitly wrap mProfCycle rather than depending on
   203  	// uint wraparound because the memRecord.future ring does not
   204  	// itself wrap at a power of two.
   205  	for {
   206  		prev := c.value.Load()
   207  		cycle := prev >> 1
   208  		cycle = (cycle + 1) % mProfCycleWrap
   209  		next := cycle << 1
   210  		if c.value.CompareAndSwap(prev, next) {
   211  			break
   212  		}
   213  	}
   214  }
   215  
   216  // newBucket allocates a bucket with the given type and number of stack entries.
   217  func newBucket(typ bucketType, nstk int) *bucket {
   218  	size := unsafe.Sizeof(bucket{}) + uintptr(nstk)*unsafe.Sizeof(uintptr(0))
   219  	switch typ {
   220  	default:
   221  		throw("invalid profile bucket type")
   222  	case memProfile:
   223  		size += unsafe.Sizeof(memRecord{})
   224  	case blockProfile, mutexProfile:
   225  		size += unsafe.Sizeof(blockRecord{})
   226  	}
   227  
   228  	b := (*bucket)(persistentalloc(size, 0, &memstats.buckhash_sys))
   229  	b.typ = typ
   230  	b.nstk = uintptr(nstk)
   231  	return b
   232  }
   233  
   234  // stk returns the slice in b holding the stack.
   235  func (b *bucket) stk() []uintptr {
   236  	stk := (*[maxStack]uintptr)(add(unsafe.Pointer(b), unsafe.Sizeof(*b)))
   237  	if b.nstk > maxStack {
   238  		// prove that slicing works; otherwise a failure requires a P
   239  		throw("bad profile stack count")
   240  	}
   241  	return stk[:b.nstk:b.nstk]
   242  }
   243  
   244  // mp returns the memRecord associated with the memProfile bucket b.
   245  func (b *bucket) mp() *memRecord {
   246  	if b.typ != memProfile {
   247  		throw("bad use of bucket.mp")
   248  	}
   249  	data := add(unsafe.Pointer(b), unsafe.Sizeof(*b)+b.nstk*unsafe.Sizeof(uintptr(0)))
   250  	return (*memRecord)(data)
   251  }
   252  
   253  // bp returns the blockRecord associated with the blockProfile bucket b.
   254  func (b *bucket) bp() *blockRecord {
   255  	if b.typ != blockProfile && b.typ != mutexProfile {
   256  		throw("bad use of bucket.bp")
   257  	}
   258  	data := add(unsafe.Pointer(b), unsafe.Sizeof(*b)+b.nstk*unsafe.Sizeof(uintptr(0)))
   259  	return (*blockRecord)(data)
   260  }
   261  
   262  // Return the bucket for stk[0:nstk], allocating new bucket if needed.
   263  func stkbucket(typ bucketType, size uintptr, stk []uintptr, alloc bool) *bucket {
   264  	bh := (*buckhashArray)(buckhash.Load())
   265  	if bh == nil {
   266  		lock(&profInsertLock)
   267  		// check again under the lock
   268  		bh = (*buckhashArray)(buckhash.Load())
   269  		if bh == nil {
   270  			bh = (*buckhashArray)(sysAlloc(unsafe.Sizeof(buckhashArray{}), &memstats.buckhash_sys))
   271  			if bh == nil {
   272  				throw("runtime: cannot allocate memory")
   273  			}
   274  			buckhash.StoreNoWB(unsafe.Pointer(bh))
   275  		}
   276  		unlock(&profInsertLock)
   277  	}
   278  
   279  	// Hash stack.
   280  	var h uintptr
   281  	for _, pc := range stk {
   282  		h += pc
   283  		h += h << 10
   284  		h ^= h >> 6
   285  	}
   286  	// hash in size
   287  	h += size
   288  	h += h << 10
   289  	h ^= h >> 6
   290  	// finalize
   291  	h += h << 3
   292  	h ^= h >> 11
   293  
   294  	i := int(h % buckHashSize)
   295  	// first check optimistically, without the lock
   296  	for b := (*bucket)(bh[i].Load()); b != nil; b = b.next {
   297  		if b.typ == typ && b.hash == h && b.size == size && eqslice(b.stk(), stk) {
   298  			return b
   299  		}
   300  	}
   301  
   302  	if !alloc {
   303  		return nil
   304  	}
   305  
   306  	lock(&profInsertLock)
   307  	// check again under the insertion lock
   308  	for b := (*bucket)(bh[i].Load()); b != nil; b = b.next {
   309  		if b.typ == typ && b.hash == h && b.size == size && eqslice(b.stk(), stk) {
   310  			unlock(&profInsertLock)
   311  			return b
   312  		}
   313  	}
   314  
   315  	// Create new bucket.
   316  	b := newBucket(typ, len(stk))
   317  	copy(b.stk(), stk)
   318  	b.hash = h
   319  	b.size = size
   320  
   321  	var allnext *atomic.UnsafePointer
   322  	if typ == memProfile {
   323  		allnext = &mbuckets
   324  	} else if typ == mutexProfile {
   325  		allnext = &xbuckets
   326  	} else {
   327  		allnext = &bbuckets
   328  	}
   329  
   330  	b.next = (*bucket)(bh[i].Load())
   331  	b.allnext = (*bucket)(allnext.Load())
   332  
   333  	bh[i].StoreNoWB(unsafe.Pointer(b))
   334  	allnext.StoreNoWB(unsafe.Pointer(b))
   335  
   336  	unlock(&profInsertLock)
   337  	return b
   338  }
   339  
   340  func eqslice(x, y []uintptr) bool {
   341  	if len(x) != len(y) {
   342  		return false
   343  	}
   344  	for i, xi := range x {
   345  		if xi != y[i] {
   346  			return false
   347  		}
   348  	}
   349  	return true
   350  }
   351  
   352  // mProf_NextCycle publishes the next heap profile cycle and creates a
   353  // fresh heap profile cycle. This operation is fast and can be done
   354  // during STW. The caller must call mProf_Flush before calling
   355  // mProf_NextCycle again.
   356  //
   357  // This is called by mark termination during STW so allocations and
   358  // frees after the world is started again count towards a new heap
   359  // profiling cycle.
   360  func mProf_NextCycle() {
   361  	mProfCycle.increment()
   362  }
   363  
   364  // mProf_Flush flushes the events from the current heap profiling
   365  // cycle into the active profile. After this it is safe to start a new
   366  // heap profiling cycle with mProf_NextCycle.
   367  //
   368  // This is called by GC after mark termination starts the world. In
   369  // contrast with mProf_NextCycle, this is somewhat expensive, but safe
   370  // to do concurrently.
   371  func mProf_Flush() {
   372  	cycle, alreadyFlushed := mProfCycle.setFlushed()
   373  	if alreadyFlushed {
   374  		return
   375  	}
   376  
   377  	index := cycle % uint32(len(memRecord{}.future))
   378  	lock(&profMemActiveLock)
   379  	lock(&profMemFutureLock[index])
   380  	mProf_FlushLocked(index)
   381  	unlock(&profMemFutureLock[index])
   382  	unlock(&profMemActiveLock)
   383  }
   384  
   385  // mProf_FlushLocked flushes the events from the heap profiling cycle at index
   386  // into the active profile. The caller must hold the lock for the active profile
   387  // (profMemActiveLock) and for the profiling cycle at index
   388  // (profMemFutureLock[index]).
   389  func mProf_FlushLocked(index uint32) {
   390  	assertLockHeld(&profMemActiveLock)
   391  	assertLockHeld(&profMemFutureLock[index])
   392  	head := (*bucket)(mbuckets.Load())
   393  	for b := head; b != nil; b = b.allnext {
   394  		mp := b.mp()
   395  
   396  		// Flush cycle C into the published profile and clear
   397  		// it for reuse.
   398  		mpc := &mp.future[index]
   399  		mp.active.add(mpc)
   400  		*mpc = memRecordCycle{}
   401  	}
   402  }
   403  
   404  // mProf_PostSweep records that all sweep frees for this GC cycle have
   405  // completed. This has the effect of publishing the heap profile
   406  // snapshot as of the last mark termination without advancing the heap
   407  // profile cycle.
   408  func mProf_PostSweep() {
   409  	// Flush cycle C+1 to the active profile so everything as of
   410  	// the last mark termination becomes visible. *Don't* advance
   411  	// the cycle, since we're still accumulating allocs in cycle
   412  	// C+2, which have to become C+1 in the next mark termination
   413  	// and so on.
   414  	cycle := mProfCycle.read() + 1
   415  
   416  	index := cycle % uint32(len(memRecord{}.future))
   417  	lock(&profMemActiveLock)
   418  	lock(&profMemFutureLock[index])
   419  	mProf_FlushLocked(index)
   420  	unlock(&profMemFutureLock[index])
   421  	unlock(&profMemActiveLock)
   422  }
   423  
   424  // Called by malloc to record a profiled block.
   425  func mProf_Malloc(p unsafe.Pointer, size uintptr) {
   426  	var stk [maxStack]uintptr
   427  	nstk := callers(4, stk[:])
   428  
   429  	index := (mProfCycle.read() + 2) % uint32(len(memRecord{}.future))
   430  
   431  	b := stkbucket(memProfile, size, stk[:nstk], true)
   432  	mp := b.mp()
   433  	mpc := &mp.future[index]
   434  
   435  	lock(&profMemFutureLock[index])
   436  	mpc.allocs++
   437  	mpc.alloc_bytes += size
   438  	unlock(&profMemFutureLock[index])
   439  
   440  	// Setprofilebucket locks a bunch of other mutexes, so we call it outside of
   441  	// the profiler locks. This reduces potential contention and chances of
   442  	// deadlocks. Since the object must be alive during the call to
   443  	// mProf_Malloc, it's fine to do this non-atomically.
   444  	systemstack(func() {
   445  		setprofilebucket(p, b)
   446  	})
   447  }
   448  
   449  // Called when freeing a profiled block.
   450  func mProf_Free(b *bucket, size uintptr) {
   451  	index := (mProfCycle.read() + 1) % uint32(len(memRecord{}.future))
   452  
   453  	mp := b.mp()
   454  	mpc := &mp.future[index]
   455  
   456  	lock(&profMemFutureLock[index])
   457  	mpc.frees++
   458  	mpc.free_bytes += size
   459  	unlock(&profMemFutureLock[index])
   460  }
   461  
   462  var blockprofilerate uint64 // in CPU ticks
   463  
   464  // SetBlockProfileRate controls the fraction of goroutine blocking events
   465  // that are reported in the blocking profile. The profiler aims to sample
   466  // an average of one blocking event per rate nanoseconds spent blocked.
   467  //
   468  // To include every blocking event in the profile, pass rate = 1.
   469  // To turn off profiling entirely, pass rate <= 0.
   470  func SetBlockProfileRate(rate int) {
   471  	var r int64
   472  	if rate <= 0 {
   473  		r = 0 // disable profiling
   474  	} else if rate == 1 {
   475  		r = 1 // profile everything
   476  	} else {
   477  		// convert ns to cycles, use float64 to prevent overflow during multiplication
   478  		r = int64(float64(rate) * float64(ticksPerSecond()) / (1000 * 1000 * 1000))
   479  		if r == 0 {
   480  			r = 1
   481  		}
   482  	}
   483  
   484  	atomic.Store64(&blockprofilerate, uint64(r))
   485  }
   486  
   487  func blockevent(cycles int64, skip int) {
   488  	if cycles <= 0 {
   489  		cycles = 1
   490  	}
   491  
   492  	rate := int64(atomic.Load64(&blockprofilerate))
   493  	if blocksampled(cycles, rate) {
   494  		saveblockevent(cycles, rate, skip+1, blockProfile)
   495  	}
   496  }
   497  
   498  // blocksampled returns true for all events where cycles >= rate. Shorter
   499  // events have a cycles/rate random chance of returning true.
   500  func blocksampled(cycles, rate int64) bool {
   501  	if rate <= 0 || (rate > cycles && cheaprand64()%rate > cycles) {
   502  		return false
   503  	}
   504  	return true
   505  }
   506  
   507  func saveblockevent(cycles, rate int64, skip int, which bucketType) {
   508  	gp := getg()
   509  	var nstk int
   510  	var stk [maxStack]uintptr
   511  	if gp.m.curg == nil || gp.m.curg == gp {
   512  		nstk = callers(skip, stk[:])
   513  	} else {
   514  		nstk = gcallers(gp.m.curg, skip, stk[:])
   515  	}
   516  
   517  	saveBlockEventStack(cycles, rate, stk[:nstk], which)
   518  }
   519  
   520  // lockTimer assists with profiling contention on runtime-internal locks.
   521  //
   522  // There are several steps between the time that an M experiences contention and
   523  // when that contention may be added to the profile. This comes from our
   524  // constraints: We need to keep the critical section of each lock small,
   525  // especially when those locks are contended. The reporting code cannot acquire
   526  // new locks until the M has released all other locks, which means no memory
   527  // allocations and encourages use of (temporary) M-local storage.
   528  //
   529  // The M will have space for storing one call stack that caused contention, and
   530  // for the magnitude of that contention. It will also have space to store the
   531  // magnitude of additional contention the M caused, since it only has space to
   532  // remember one call stack and might encounter several contention events before
   533  // it releases all of its locks and is thus able to transfer the local buffer
   534  // into the profile.
   535  //
   536  // The M will collect the call stack when it unlocks the contended lock. That
   537  // minimizes the impact on the critical section of the contended lock, and
   538  // matches the mutex profile's behavior for contention in sync.Mutex: measured
   539  // at the Unlock method.
   540  //
   541  // The profile for contention on sync.Mutex blames the caller of Unlock for the
   542  // amount of contention experienced by the callers of Lock which had to wait.
   543  // When there are several critical sections, this allows identifying which of
   544  // them is responsible.
   545  //
   546  // Matching that behavior for runtime-internal locks will require identifying
   547  // which Ms are blocked on the mutex. The semaphore-based implementation is
   548  // ready to allow that, but the futex-based implementation will require a bit
   549  // more work. Until then, we report contention on runtime-internal locks with a
   550  // call stack taken from the unlock call (like the rest of the user-space
   551  // "mutex" profile), but assign it a duration value based on how long the
   552  // previous lock call took (like the user-space "block" profile).
   553  //
   554  // Thus, reporting the call stacks of runtime-internal lock contention is
   555  // guarded by GODEBUG for now. Set GODEBUG=runtimecontentionstacks=1 to enable.
   556  //
   557  // TODO(rhysh): plumb through the delay duration, remove GODEBUG, update comment
   558  //
   559  // The M will track this by storing a pointer to the lock; lock/unlock pairs for
   560  // runtime-internal locks are always on the same M.
   561  //
   562  // Together, that demands several steps for recording contention. First, when
   563  // finally acquiring a contended lock, the M decides whether it should plan to
   564  // profile that event by storing a pointer to the lock in its "to be profiled
   565  // upon unlock" field. If that field is already set, it uses the relative
   566  // magnitudes to weight a random choice between itself and the other lock, with
   567  // the loser's time being added to the "additional contention" field. Otherwise
   568  // if the M's call stack buffer is occupied, it does the comparison against that
   569  // sample's magnitude.
   570  //
   571  // Second, having unlocked a mutex the M checks to see if it should capture the
   572  // call stack into its local buffer. Finally, when the M unlocks its last mutex,
   573  // it transfers the local buffer into the profile. As part of that step, it also
   574  // transfers any "additional contention" time to the profile. Any lock
   575  // contention that it experiences while adding samples to the profile will be
   576  // recorded later as "additional contention" and not include a call stack, to
   577  // avoid an echo.
   578  type lockTimer struct {
   579  	lock      *mutex
   580  	timeRate  int64
   581  	timeStart int64
   582  	tickStart int64
   583  }
   584  
   585  func (lt *lockTimer) begin() {
   586  	rate := int64(atomic.Load64(&mutexprofilerate))
   587  
   588  	lt.timeRate = gTrackingPeriod
   589  	if rate != 0 && rate < lt.timeRate {
   590  		lt.timeRate = rate
   591  	}
   592  	if int64(cheaprand())%lt.timeRate == 0 {
   593  		lt.timeStart = nanotime()
   594  	}
   595  
   596  	if rate > 0 && int64(cheaprand())%rate == 0 {
   597  		lt.tickStart = cputicks()
   598  	}
   599  }
   600  
   601  func (lt *lockTimer) end() {
   602  	gp := getg()
   603  
   604  	if lt.timeStart != 0 {
   605  		nowTime := nanotime()
   606  		gp.m.mLockProfile.waitTime.Add((nowTime - lt.timeStart) * lt.timeRate)
   607  	}
   608  
   609  	if lt.tickStart != 0 {
   610  		nowTick := cputicks()
   611  		gp.m.mLockProfile.recordLock(nowTick-lt.tickStart, lt.lock)
   612  	}
   613  }
   614  
   615  type mLockProfile struct {
   616  	waitTime   atomic.Int64      // total nanoseconds spent waiting in runtime.lockWithRank
   617  	stack      [maxStack]uintptr // stack that experienced contention in runtime.lockWithRank
   618  	pending    uintptr           // *mutex that experienced contention (to be traceback-ed)
   619  	cycles     int64             // cycles attributable to "pending" (if set), otherwise to "stack"
   620  	cyclesLost int64             // contention for which we weren't able to record a call stack
   621  	disabled   bool              // attribute all time to "lost"
   622  }
   623  
   624  func (prof *mLockProfile) recordLock(cycles int64, l *mutex) {
   625  	if cycles <= 0 {
   626  		return
   627  	}
   628  
   629  	if prof.disabled {
   630  		// We're experiencing contention while attempting to report contention.
   631  		// Make a note of its magnitude, but don't allow it to be the sole cause
   632  		// of another contention report.
   633  		prof.cyclesLost += cycles
   634  		return
   635  	}
   636  
   637  	if uintptr(unsafe.Pointer(l)) == prof.pending {
   638  		// Optimization: we'd already planned to profile this same lock (though
   639  		// possibly from a different unlock site).
   640  		prof.cycles += cycles
   641  		return
   642  	}
   643  
   644  	if prev := prof.cycles; prev > 0 {
   645  		// We can only store one call stack for runtime-internal lock contention
   646  		// on this M, and we've already got one. Decide which should stay, and
   647  		// add the other to the report for runtime._LostContendedRuntimeLock.
   648  		prevScore := uint64(cheaprand64()) % uint64(prev)
   649  		thisScore := uint64(cheaprand64()) % uint64(cycles)
   650  		if prevScore > thisScore {
   651  			prof.cyclesLost += cycles
   652  			return
   653  		} else {
   654  			prof.cyclesLost += prev
   655  		}
   656  	}
   657  	// Saving the *mutex as a uintptr is safe because:
   658  	//  - lockrank_on.go does this too, which gives it regular exercise
   659  	//  - the lock would only move if it's stack allocated, which means it
   660  	//      cannot experience multi-M contention
   661  	prof.pending = uintptr(unsafe.Pointer(l))
   662  	prof.cycles = cycles
   663  }
   664  
   665  // From unlock2, we might not be holding a p in this code.
   666  //
   667  //go:nowritebarrierrec
   668  func (prof *mLockProfile) recordUnlock(l *mutex) {
   669  	if uintptr(unsafe.Pointer(l)) == prof.pending {
   670  		prof.captureStack()
   671  	}
   672  	if gp := getg(); gp.m.locks == 1 && gp.m.mLockProfile.cycles != 0 {
   673  		prof.store()
   674  	}
   675  }
   676  
   677  func (prof *mLockProfile) captureStack() {
   678  	skip := 3 // runtime.(*mLockProfile).recordUnlock runtime.unlock2 runtime.unlockWithRank
   679  	if staticLockRanking {
   680  		// When static lock ranking is enabled, we'll always be on the system
   681  		// stack at this point. There will be a runtime.unlockWithRank.func1
   682  		// frame, and if the call to runtime.unlock took place on a user stack
   683  		// then there'll also be a runtime.systemstack frame. To keep stack
   684  		// traces somewhat consistent whether or not static lock ranking is
   685  		// enabled, we'd like to skip those. But it's hard to tell how long
   686  		// we've been on the system stack so accept an extra frame in that case,
   687  		// with a leaf of "runtime.unlockWithRank runtime.unlock" instead of
   688  		// "runtime.unlock".
   689  		skip += 1 // runtime.unlockWithRank.func1
   690  	}
   691  	prof.pending = 0
   692  
   693  	if debug.runtimeContentionStacks.Load() == 0 {
   694  		prof.stack[0] = abi.FuncPCABIInternal(_LostContendedRuntimeLock) + sys.PCQuantum
   695  		prof.stack[1] = 0
   696  		return
   697  	}
   698  
   699  	var nstk int
   700  	gp := getg()
   701  	sp := getcallersp()
   702  	pc := getcallerpc()
   703  	systemstack(func() {
   704  		var u unwinder
   705  		u.initAt(pc, sp, 0, gp, unwindSilentErrors|unwindJumpStack)
   706  		nstk = tracebackPCs(&u, skip, prof.stack[:])
   707  	})
   708  	if nstk < len(prof.stack) {
   709  		prof.stack[nstk] = 0
   710  	}
   711  }
   712  
   713  func (prof *mLockProfile) store() {
   714  	// Report any contention we experience within this function as "lost"; it's
   715  	// important that the act of reporting a contention event not lead to a
   716  	// reportable contention event. This also means we can use prof.stack
   717  	// without copying, since it won't change during this function.
   718  	mp := acquirem()
   719  	prof.disabled = true
   720  
   721  	nstk := maxStack
   722  	for i := 0; i < nstk; i++ {
   723  		if pc := prof.stack[i]; pc == 0 {
   724  			nstk = i
   725  			break
   726  		}
   727  	}
   728  
   729  	cycles, lost := prof.cycles, prof.cyclesLost
   730  	prof.cycles, prof.cyclesLost = 0, 0
   731  
   732  	rate := int64(atomic.Load64(&mutexprofilerate))
   733  	saveBlockEventStack(cycles, rate, prof.stack[:nstk], mutexProfile)
   734  	if lost > 0 {
   735  		lostStk := [...]uintptr{
   736  			abi.FuncPCABIInternal(_LostContendedRuntimeLock) + sys.PCQuantum,
   737  		}
   738  		saveBlockEventStack(lost, rate, lostStk[:], mutexProfile)
   739  	}
   740  
   741  	prof.disabled = false
   742  	releasem(mp)
   743  }
   744  
   745  func saveBlockEventStack(cycles, rate int64, stk []uintptr, which bucketType) {
   746  	b := stkbucket(which, 0, stk, true)
   747  	bp := b.bp()
   748  
   749  	lock(&profBlockLock)
   750  	// We want to up-scale the count and cycles according to the
   751  	// probability that the event was sampled. For block profile events,
   752  	// the sample probability is 1 if cycles >= rate, and cycles / rate
   753  	// otherwise. For mutex profile events, the sample probability is 1 / rate.
   754  	// We scale the events by 1 / (probability the event was sampled).
   755  	if which == blockProfile && cycles < rate {
   756  		// Remove sampling bias, see discussion on http://golang.org/cl/299991.
   757  		bp.count += float64(rate) / float64(cycles)
   758  		bp.cycles += rate
   759  	} else if which == mutexProfile {
   760  		bp.count += float64(rate)
   761  		bp.cycles += rate * cycles
   762  	} else {
   763  		bp.count++
   764  		bp.cycles += cycles
   765  	}
   766  	unlock(&profBlockLock)
   767  }
   768  
   769  var mutexprofilerate uint64 // fraction sampled
   770  
   771  // SetMutexProfileFraction controls the fraction of mutex contention events
   772  // that are reported in the mutex profile. On average 1/rate events are
   773  // reported. The previous rate is returned.
   774  //
   775  // To turn off profiling entirely, pass rate 0.
   776  // To just read the current rate, pass rate < 0.
   777  // (For n>1 the details of sampling may change.)
   778  func SetMutexProfileFraction(rate int) int {
   779  	if rate < 0 {
   780  		return int(mutexprofilerate)
   781  	}
   782  	old := mutexprofilerate
   783  	atomic.Store64(&mutexprofilerate, uint64(rate))
   784  	return int(old)
   785  }
   786  
   787  //go:linkname mutexevent sync.event
   788  func mutexevent(cycles int64, skip int) {
   789  	if cycles < 0 {
   790  		cycles = 0
   791  	}
   792  	rate := int64(atomic.Load64(&mutexprofilerate))
   793  	if rate > 0 && cheaprand64()%rate == 0 {
   794  		saveblockevent(cycles, rate, skip+1, mutexProfile)
   795  	}
   796  }
   797  
   798  // Go interface to profile data.
   799  
   800  // A StackRecord describes a single execution stack.
   801  type StackRecord struct {
   802  	Stack0 [32]uintptr // stack trace for this record; ends at first 0 entry
   803  }
   804  
   805  // Stack returns the stack trace associated with the record,
   806  // a prefix of r.Stack0.
   807  func (r *StackRecord) Stack() []uintptr {
   808  	for i, v := range r.Stack0 {
   809  		if v == 0 {
   810  			return r.Stack0[0:i]
   811  		}
   812  	}
   813  	return r.Stack0[0:]
   814  }
   815  
   816  // MemProfileRate controls the fraction of memory allocations
   817  // that are recorded and reported in the memory profile.
   818  // The profiler aims to sample an average of
   819  // one allocation per MemProfileRate bytes allocated.
   820  //
   821  // To include every allocated block in the profile, set MemProfileRate to 1.
   822  // To turn off profiling entirely, set MemProfileRate to 0.
   823  //
   824  // The tools that process the memory profiles assume that the
   825  // profile rate is constant across the lifetime of the program
   826  // and equal to the current value. Programs that change the
   827  // memory profiling rate should do so just once, as early as
   828  // possible in the execution of the program (for example,
   829  // at the beginning of main).
   830  var MemProfileRate int = 512 * 1024
   831  
   832  // disableMemoryProfiling is set by the linker if runtime.MemProfile
   833  // is not used and the link type guarantees nobody else could use it
   834  // elsewhere.
   835  var disableMemoryProfiling bool
   836  
   837  // A MemProfileRecord describes the live objects allocated
   838  // by a particular call sequence (stack trace).
   839  type MemProfileRecord struct {
   840  	AllocBytes, FreeBytes     int64       // number of bytes allocated, freed
   841  	AllocObjects, FreeObjects int64       // number of objects allocated, freed
   842  	Stack0                    [32]uintptr // stack trace for this record; ends at first 0 entry
   843  }
   844  
   845  // InUseBytes returns the number of bytes in use (AllocBytes - FreeBytes).
   846  func (r *MemProfileRecord) InUseBytes() int64 { return r.AllocBytes - r.FreeBytes }
   847  
   848  // InUseObjects returns the number of objects in use (AllocObjects - FreeObjects).
   849  func (r *MemProfileRecord) InUseObjects() int64 {
   850  	return r.AllocObjects - r.FreeObjects
   851  }
   852  
   853  // Stack returns the stack trace associated with the record,
   854  // a prefix of r.Stack0.
   855  func (r *MemProfileRecord) Stack() []uintptr {
   856  	for i, v := range r.Stack0 {
   857  		if v == 0 {
   858  			return r.Stack0[0:i]
   859  		}
   860  	}
   861  	return r.Stack0[0:]
   862  }
   863  
   864  // MemProfile returns a profile of memory allocated and freed per allocation
   865  // site.
   866  //
   867  // MemProfile returns n, the number of records in the current memory profile.
   868  // If len(p) >= n, MemProfile copies the profile into p and returns n, true.
   869  // If len(p) < n, MemProfile does not change p and returns n, false.
   870  //
   871  // If inuseZero is true, the profile includes allocation records
   872  // where r.AllocBytes > 0 but r.AllocBytes == r.FreeBytes.
   873  // These are sites where memory was allocated, but it has all
   874  // been released back to the runtime.
   875  //
   876  // The returned profile may be up to two garbage collection cycles old.
   877  // This is to avoid skewing the profile toward allocations; because
   878  // allocations happen in real time but frees are delayed until the garbage
   879  // collector performs sweeping, the profile only accounts for allocations
   880  // that have had a chance to be freed by the garbage collector.
   881  //
   882  // Most clients should use the runtime/pprof package or
   883  // the testing package's -test.memprofile flag instead
   884  // of calling MemProfile directly.
   885  func MemProfile(p []MemProfileRecord, inuseZero bool) (n int, ok bool) {
   886  	cycle := mProfCycle.read()
   887  	// If we're between mProf_NextCycle and mProf_Flush, take care
   888  	// of flushing to the active profile so we only have to look
   889  	// at the active profile below.
   890  	index := cycle % uint32(len(memRecord{}.future))
   891  	lock(&profMemActiveLock)
   892  	lock(&profMemFutureLock[index])
   893  	mProf_FlushLocked(index)
   894  	unlock(&profMemFutureLock[index])
   895  	clear := true
   896  	head := (*bucket)(mbuckets.Load())
   897  	for b := head; b != nil; b = b.allnext {
   898  		mp := b.mp()
   899  		if inuseZero || mp.active.alloc_bytes != mp.active.free_bytes {
   900  			n++
   901  		}
   902  		if mp.active.allocs != 0 || mp.active.frees != 0 {
   903  			clear = false
   904  		}
   905  	}
   906  	if clear {
   907  		// Absolutely no data, suggesting that a garbage collection
   908  		// has not yet happened. In order to allow profiling when
   909  		// garbage collection is disabled from the beginning of execution,
   910  		// accumulate all of the cycles, and recount buckets.
   911  		n = 0
   912  		for b := head; b != nil; b = b.allnext {
   913  			mp := b.mp()
   914  			for c := range mp.future {
   915  				lock(&profMemFutureLock[c])
   916  				mp.active.add(&mp.future[c])
   917  				mp.future[c] = memRecordCycle{}
   918  				unlock(&profMemFutureLock[c])
   919  			}
   920  			if inuseZero || mp.active.alloc_bytes != mp.active.free_bytes {
   921  				n++
   922  			}
   923  		}
   924  	}
   925  	if n <= len(p) {
   926  		ok = true
   927  		idx := 0
   928  		for b := head; b != nil; b = b.allnext {
   929  			mp := b.mp()
   930  			if inuseZero || mp.active.alloc_bytes != mp.active.free_bytes {
   931  				record(&p[idx], b)
   932  				idx++
   933  			}
   934  		}
   935  	}
   936  	unlock(&profMemActiveLock)
   937  	return
   938  }
   939  
   940  // Write b's data to r.
   941  func record(r *MemProfileRecord, b *bucket) {
   942  	mp := b.mp()
   943  	r.AllocBytes = int64(mp.active.alloc_bytes)
   944  	r.FreeBytes = int64(mp.active.free_bytes)
   945  	r.AllocObjects = int64(mp.active.allocs)
   946  	r.FreeObjects = int64(mp.active.frees)
   947  	if raceenabled {
   948  		racewriterangepc(unsafe.Pointer(&r.Stack0[0]), unsafe.Sizeof(r.Stack0), getcallerpc(), abi.FuncPCABIInternal(MemProfile))
   949  	}
   950  	if msanenabled {
   951  		msanwrite(unsafe.Pointer(&r.Stack0[0]), unsafe.Sizeof(r.Stack0))
   952  	}
   953  	if asanenabled {
   954  		asanwrite(unsafe.Pointer(&r.Stack0[0]), unsafe.Sizeof(r.Stack0))
   955  	}
   956  	copy(r.Stack0[:], b.stk())
   957  	for i := int(b.nstk); i < len(r.Stack0); i++ {
   958  		r.Stack0[i] = 0
   959  	}
   960  }
   961  
   962  func iterate_memprof(fn func(*bucket, uintptr, *uintptr, uintptr, uintptr, uintptr)) {
   963  	lock(&profMemActiveLock)
   964  	head := (*bucket)(mbuckets.Load())
   965  	for b := head; b != nil; b = b.allnext {
   966  		mp := b.mp()
   967  		fn(b, b.nstk, &b.stk()[0], b.size, mp.active.allocs, mp.active.frees)
   968  	}
   969  	unlock(&profMemActiveLock)
   970  }
   971  
   972  // BlockProfileRecord describes blocking events originated
   973  // at a particular call sequence (stack trace).
   974  type BlockProfileRecord struct {
   975  	Count  int64
   976  	Cycles int64
   977  	StackRecord
   978  }
   979  
   980  // BlockProfile returns n, the number of records in the current blocking profile.
   981  // If len(p) >= n, BlockProfile copies the profile into p and returns n, true.
   982  // If len(p) < n, BlockProfile does not change p and returns n, false.
   983  //
   984  // Most clients should use the [runtime/pprof] package or
   985  // the [testing] package's -test.blockprofile flag instead
   986  // of calling BlockProfile directly.
   987  func BlockProfile(p []BlockProfileRecord) (n int, ok bool) {
   988  	lock(&profBlockLock)
   989  	head := (*bucket)(bbuckets.Load())
   990  	for b := head; b != nil; b = b.allnext {
   991  		n++
   992  	}
   993  	if n <= len(p) {
   994  		ok = true
   995  		for b := head; b != nil; b = b.allnext {
   996  			bp := b.bp()
   997  			r := &p[0]
   998  			r.Count = int64(bp.count)
   999  			// Prevent callers from having to worry about division by zero errors.
  1000  			// See discussion on http://golang.org/cl/299991.
  1001  			if r.Count == 0 {
  1002  				r.Count = 1
  1003  			}
  1004  			r.Cycles = bp.cycles
  1005  			if raceenabled {
  1006  				racewriterangepc(unsafe.Pointer(&r.Stack0[0]), unsafe.Sizeof(r.Stack0), getcallerpc(), abi.FuncPCABIInternal(BlockProfile))
  1007  			}
  1008  			if msanenabled {
  1009  				msanwrite(unsafe.Pointer(&r.Stack0[0]), unsafe.Sizeof(r.Stack0))
  1010  			}
  1011  			if asanenabled {
  1012  				asanwrite(unsafe.Pointer(&r.Stack0[0]), unsafe.Sizeof(r.Stack0))
  1013  			}
  1014  			i := copy(r.Stack0[:], b.stk())
  1015  			for ; i < len(r.Stack0); i++ {
  1016  				r.Stack0[i] = 0
  1017  			}
  1018  			p = p[1:]
  1019  		}
  1020  	}
  1021  	unlock(&profBlockLock)
  1022  	return
  1023  }
  1024  
  1025  // MutexProfile returns n, the number of records in the current mutex profile.
  1026  // If len(p) >= n, MutexProfile copies the profile into p and returns n, true.
  1027  // Otherwise, MutexProfile does not change p, and returns n, false.
  1028  //
  1029  // Most clients should use the [runtime/pprof] package
  1030  // instead of calling MutexProfile directly.
  1031  func MutexProfile(p []BlockProfileRecord) (n int, ok bool) {
  1032  	lock(&profBlockLock)
  1033  	head := (*bucket)(xbuckets.Load())
  1034  	for b := head; b != nil; b = b.allnext {
  1035  		n++
  1036  	}
  1037  	if n <= len(p) {
  1038  		ok = true
  1039  		for b := head; b != nil; b = b.allnext {
  1040  			bp := b.bp()
  1041  			r := &p[0]
  1042  			r.Count = int64(bp.count)
  1043  			r.Cycles = bp.cycles
  1044  			i := copy(r.Stack0[:], b.stk())
  1045  			for ; i < len(r.Stack0); i++ {
  1046  				r.Stack0[i] = 0
  1047  			}
  1048  			p = p[1:]
  1049  		}
  1050  	}
  1051  	unlock(&profBlockLock)
  1052  	return
  1053  }
  1054  
  1055  // ThreadCreateProfile returns n, the number of records in the thread creation profile.
  1056  // If len(p) >= n, ThreadCreateProfile copies the profile into p and returns n, true.
  1057  // If len(p) < n, ThreadCreateProfile does not change p and returns n, false.
  1058  //
  1059  // Most clients should use the runtime/pprof package instead
  1060  // of calling ThreadCreateProfile directly.
  1061  func ThreadCreateProfile(p []StackRecord) (n int, ok bool) {
  1062  	first := (*m)(atomic.Loadp(unsafe.Pointer(&allm)))
  1063  	for mp := first; mp != nil; mp = mp.alllink {
  1064  		n++
  1065  	}
  1066  	if n <= len(p) {
  1067  		ok = true
  1068  		i := 0
  1069  		for mp := first; mp != nil; mp = mp.alllink {
  1070  			p[i].Stack0 = mp.createstack
  1071  			i++
  1072  		}
  1073  	}
  1074  	return
  1075  }
  1076  
  1077  //go:linkname runtime_goroutineProfileWithLabels runtime/pprof.runtime_goroutineProfileWithLabels
  1078  func runtime_goroutineProfileWithLabels(p []StackRecord, labels []unsafe.Pointer) (n int, ok bool) {
  1079  	return goroutineProfileWithLabels(p, labels)
  1080  }
  1081  
  1082  // labels may be nil. If labels is non-nil, it must have the same length as p.
  1083  func goroutineProfileWithLabels(p []StackRecord, labels []unsafe.Pointer) (n int, ok bool) {
  1084  	if labels != nil && len(labels) != len(p) {
  1085  		labels = nil
  1086  	}
  1087  
  1088  	return goroutineProfileWithLabelsConcurrent(p, labels)
  1089  }
  1090  
  1091  var goroutineProfile = struct {
  1092  	sema    uint32
  1093  	active  bool
  1094  	offset  atomic.Int64
  1095  	records []StackRecord
  1096  	labels  []unsafe.Pointer
  1097  }{
  1098  	sema: 1,
  1099  }
  1100  
  1101  // goroutineProfileState indicates the status of a goroutine's stack for the
  1102  // current in-progress goroutine profile. Goroutines' stacks are initially
  1103  // "Absent" from the profile, and end up "Satisfied" by the time the profile is
  1104  // complete. While a goroutine's stack is being captured, its
  1105  // goroutineProfileState will be "InProgress" and it will not be able to run
  1106  // until the capture completes and the state moves to "Satisfied".
  1107  //
  1108  // Some goroutines (the finalizer goroutine, which at various times can be
  1109  // either a "system" or a "user" goroutine, and the goroutine that is
  1110  // coordinating the profile, any goroutines created during the profile) move
  1111  // directly to the "Satisfied" state.
  1112  type goroutineProfileState uint32
  1113  
  1114  const (
  1115  	goroutineProfileAbsent goroutineProfileState = iota
  1116  	goroutineProfileInProgress
  1117  	goroutineProfileSatisfied
  1118  )
  1119  
  1120  type goroutineProfileStateHolder atomic.Uint32
  1121  
  1122  func (p *goroutineProfileStateHolder) Load() goroutineProfileState {
  1123  	return goroutineProfileState((*atomic.Uint32)(p).Load())
  1124  }
  1125  
  1126  func (p *goroutineProfileStateHolder) Store(value goroutineProfileState) {
  1127  	(*atomic.Uint32)(p).Store(uint32(value))
  1128  }
  1129  
  1130  func (p *goroutineProfileStateHolder) CompareAndSwap(old, new goroutineProfileState) bool {
  1131  	return (*atomic.Uint32)(p).CompareAndSwap(uint32(old), uint32(new))
  1132  }
  1133  
  1134  func goroutineProfileWithLabelsConcurrent(p []StackRecord, labels []unsafe.Pointer) (n int, ok bool) {
  1135  	semacquire(&goroutineProfile.sema)
  1136  
  1137  	ourg := getg()
  1138  
  1139  	stw := stopTheWorld(stwGoroutineProfile)
  1140  	// Using gcount while the world is stopped should give us a consistent view
  1141  	// of the number of live goroutines, minus the number of goroutines that are
  1142  	// alive and permanently marked as "system". But to make this count agree
  1143  	// with what we'd get from isSystemGoroutine, we need special handling for
  1144  	// goroutines that can vary between user and system to ensure that the count
  1145  	// doesn't change during the collection. So, check the finalizer goroutine
  1146  	// in particular.
  1147  	n = int(gcount())
  1148  	if fingStatus.Load()&fingRunningFinalizer != 0 {
  1149  		n++
  1150  	}
  1151  
  1152  	if n > len(p) {
  1153  		// There's not enough space in p to store the whole profile, so (per the
  1154  		// contract of runtime.GoroutineProfile) we're not allowed to write to p
  1155  		// at all and must return n, false.
  1156  		startTheWorld(stw)
  1157  		semrelease(&goroutineProfile.sema)
  1158  		return n, false
  1159  	}
  1160  
  1161  	// Save current goroutine.
  1162  	sp := getcallersp()
  1163  	pc := getcallerpc()
  1164  	systemstack(func() {
  1165  		saveg(pc, sp, ourg, &p[0])
  1166  	})
  1167  	if labels != nil {
  1168  		labels[0] = ourg.labels
  1169  	}
  1170  	ourg.goroutineProfiled.Store(goroutineProfileSatisfied)
  1171  	goroutineProfile.offset.Store(1)
  1172  
  1173  	// Prepare for all other goroutines to enter the profile. Aside from ourg,
  1174  	// every goroutine struct in the allgs list has its goroutineProfiled field
  1175  	// cleared. Any goroutine created from this point on (while
  1176  	// goroutineProfile.active is set) will start with its goroutineProfiled
  1177  	// field set to goroutineProfileSatisfied.
  1178  	goroutineProfile.active = true
  1179  	goroutineProfile.records = p
  1180  	goroutineProfile.labels = labels
  1181  	// The finalizer goroutine needs special handling because it can vary over
  1182  	// time between being a user goroutine (eligible for this profile) and a
  1183  	// system goroutine (to be excluded). Pick one before restarting the world.
  1184  	if fing != nil {
  1185  		fing.goroutineProfiled.Store(goroutineProfileSatisfied)
  1186  		if readgstatus(fing) != _Gdead && !isSystemGoroutine(fing, false) {
  1187  			doRecordGoroutineProfile(fing)
  1188  		}
  1189  	}
  1190  	startTheWorld(stw)
  1191  
  1192  	// Visit each goroutine that existed as of the startTheWorld call above.
  1193  	//
  1194  	// New goroutines may not be in this list, but we didn't want to know about
  1195  	// them anyway. If they do appear in this list (via reusing a dead goroutine
  1196  	// struct, or racing to launch between the world restarting and us getting
  1197  	// the list), they will already have their goroutineProfiled field set to
  1198  	// goroutineProfileSatisfied before their state transitions out of _Gdead.
  1199  	//
  1200  	// Any goroutine that the scheduler tries to execute concurrently with this
  1201  	// call will start by adding itself to the profile (before the act of
  1202  	// executing can cause any changes in its stack).
  1203  	forEachGRace(func(gp1 *g) {
  1204  		tryRecordGoroutineProfile(gp1, Gosched)
  1205  	})
  1206  
  1207  	stw = stopTheWorld(stwGoroutineProfileCleanup)
  1208  	endOffset := goroutineProfile.offset.Swap(0)
  1209  	goroutineProfile.active = false
  1210  	goroutineProfile.records = nil
  1211  	goroutineProfile.labels = nil
  1212  	startTheWorld(stw)
  1213  
  1214  	// Restore the invariant that every goroutine struct in allgs has its
  1215  	// goroutineProfiled field cleared.
  1216  	forEachGRace(func(gp1 *g) {
  1217  		gp1.goroutineProfiled.Store(goroutineProfileAbsent)
  1218  	})
  1219  
  1220  	if raceenabled {
  1221  		raceacquire(unsafe.Pointer(&labelSync))
  1222  	}
  1223  
  1224  	if n != int(endOffset) {
  1225  		// It's a big surprise that the number of goroutines changed while we
  1226  		// were collecting the profile. But probably better to return a
  1227  		// truncated profile than to crash the whole process.
  1228  		//
  1229  		// For instance, needm moves a goroutine out of the _Gdead state and so
  1230  		// might be able to change the goroutine count without interacting with
  1231  		// the scheduler. For code like that, the race windows are small and the
  1232  		// combination of features is uncommon, so it's hard to be (and remain)
  1233  		// sure we've caught them all.
  1234  	}
  1235  
  1236  	semrelease(&goroutineProfile.sema)
  1237  	return n, true
  1238  }
  1239  
  1240  // tryRecordGoroutineProfileWB asserts that write barriers are allowed and calls
  1241  // tryRecordGoroutineProfile.
  1242  //
  1243  //go:yeswritebarrierrec
  1244  func tryRecordGoroutineProfileWB(gp1 *g) {
  1245  	if getg().m.p.ptr() == nil {
  1246  		throw("no P available, write barriers are forbidden")
  1247  	}
  1248  	tryRecordGoroutineProfile(gp1, osyield)
  1249  }
  1250  
  1251  // tryRecordGoroutineProfile ensures that gp1 has the appropriate representation
  1252  // in the current goroutine profile: either that it should not be profiled, or
  1253  // that a snapshot of its call stack and labels are now in the profile.
  1254  func tryRecordGoroutineProfile(gp1 *g, yield func()) {
  1255  	if readgstatus(gp1) == _Gdead {
  1256  		// Dead goroutines should not appear in the profile. Goroutines that
  1257  		// start while profile collection is active will get goroutineProfiled
  1258  		// set to goroutineProfileSatisfied before transitioning out of _Gdead,
  1259  		// so here we check _Gdead first.
  1260  		return
  1261  	}
  1262  	if isSystemGoroutine(gp1, true) {
  1263  		// System goroutines should not appear in the profile. (The finalizer
  1264  		// goroutine is marked as "already profiled".)
  1265  		return
  1266  	}
  1267  
  1268  	for {
  1269  		prev := gp1.goroutineProfiled.Load()
  1270  		if prev == goroutineProfileSatisfied {
  1271  			// This goroutine is already in the profile (or is new since the
  1272  			// start of collection, so shouldn't appear in the profile).
  1273  			break
  1274  		}
  1275  		if prev == goroutineProfileInProgress {
  1276  			// Something else is adding gp1 to the goroutine profile right now.
  1277  			// Give that a moment to finish.
  1278  			yield()
  1279  			continue
  1280  		}
  1281  
  1282  		// While we have gp1.goroutineProfiled set to
  1283  		// goroutineProfileInProgress, gp1 may appear _Grunnable but will not
  1284  		// actually be able to run. Disable preemption for ourselves, to make
  1285  		// sure we finish profiling gp1 right away instead of leaving it stuck
  1286  		// in this limbo.
  1287  		mp := acquirem()
  1288  		if gp1.goroutineProfiled.CompareAndSwap(goroutineProfileAbsent, goroutineProfileInProgress) {
  1289  			doRecordGoroutineProfile(gp1)
  1290  			gp1.goroutineProfiled.Store(goroutineProfileSatisfied)
  1291  		}
  1292  		releasem(mp)
  1293  	}
  1294  }
  1295  
  1296  // doRecordGoroutineProfile writes gp1's call stack and labels to an in-progress
  1297  // goroutine profile. Preemption is disabled.
  1298  //
  1299  // This may be called via tryRecordGoroutineProfile in two ways: by the
  1300  // goroutine that is coordinating the goroutine profile (running on its own
  1301  // stack), or from the scheduler in preparation to execute gp1 (running on the
  1302  // system stack).
  1303  func doRecordGoroutineProfile(gp1 *g) {
  1304  	if readgstatus(gp1) == _Grunning {
  1305  		print("doRecordGoroutineProfile gp1=", gp1.goid, "\n")
  1306  		throw("cannot read stack of running goroutine")
  1307  	}
  1308  
  1309  	offset := int(goroutineProfile.offset.Add(1)) - 1
  1310  
  1311  	if offset >= len(goroutineProfile.records) {
  1312  		// Should be impossible, but better to return a truncated profile than
  1313  		// to crash the entire process at this point. Instead, deal with it in
  1314  		// goroutineProfileWithLabelsConcurrent where we have more context.
  1315  		return
  1316  	}
  1317  
  1318  	// saveg calls gentraceback, which may call cgo traceback functions. When
  1319  	// called from the scheduler, this is on the system stack already so
  1320  	// traceback.go:cgoContextPCs will avoid calling back into the scheduler.
  1321  	//
  1322  	// When called from the goroutine coordinating the profile, we still have
  1323  	// set gp1.goroutineProfiled to goroutineProfileInProgress and so are still
  1324  	// preventing it from being truly _Grunnable. So we'll use the system stack
  1325  	// to avoid schedule delays.
  1326  	systemstack(func() { saveg(^uintptr(0), ^uintptr(0), gp1, &goroutineProfile.records[offset]) })
  1327  
  1328  	if goroutineProfile.labels != nil {
  1329  		goroutineProfile.labels[offset] = gp1.labels
  1330  	}
  1331  }
  1332  
  1333  func goroutineProfileWithLabelsSync(p []StackRecord, labels []unsafe.Pointer) (n int, ok bool) {
  1334  	gp := getg()
  1335  
  1336  	isOK := func(gp1 *g) bool {
  1337  		// Checking isSystemGoroutine here makes GoroutineProfile
  1338  		// consistent with both NumGoroutine and Stack.
  1339  		return gp1 != gp && readgstatus(gp1) != _Gdead && !isSystemGoroutine(gp1, false)
  1340  	}
  1341  
  1342  	stw := stopTheWorld(stwGoroutineProfile)
  1343  
  1344  	// World is stopped, no locking required.
  1345  	n = 1
  1346  	forEachGRace(func(gp1 *g) {
  1347  		if isOK(gp1) {
  1348  			n++
  1349  		}
  1350  	})
  1351  
  1352  	if n <= len(p) {
  1353  		ok = true
  1354  		r, lbl := p, labels
  1355  
  1356  		// Save current goroutine.
  1357  		sp := getcallersp()
  1358  		pc := getcallerpc()
  1359  		systemstack(func() {
  1360  			saveg(pc, sp, gp, &r[0])
  1361  		})
  1362  		r = r[1:]
  1363  
  1364  		// If we have a place to put our goroutine labelmap, insert it there.
  1365  		if labels != nil {
  1366  			lbl[0] = gp.labels
  1367  			lbl = lbl[1:]
  1368  		}
  1369  
  1370  		// Save other goroutines.
  1371  		forEachGRace(func(gp1 *g) {
  1372  			if !isOK(gp1) {
  1373  				return
  1374  			}
  1375  
  1376  			if len(r) == 0 {
  1377  				// Should be impossible, but better to return a
  1378  				// truncated profile than to crash the entire process.
  1379  				return
  1380  			}
  1381  			// saveg calls gentraceback, which may call cgo traceback functions.
  1382  			// The world is stopped, so it cannot use cgocall (which will be
  1383  			// blocked at exitsyscall). Do it on the system stack so it won't
  1384  			// call into the schedular (see traceback.go:cgoContextPCs).
  1385  			systemstack(func() { saveg(^uintptr(0), ^uintptr(0), gp1, &r[0]) })
  1386  			if labels != nil {
  1387  				lbl[0] = gp1.labels
  1388  				lbl = lbl[1:]
  1389  			}
  1390  			r = r[1:]
  1391  		})
  1392  	}
  1393  
  1394  	if raceenabled {
  1395  		raceacquire(unsafe.Pointer(&labelSync))
  1396  	}
  1397  
  1398  	startTheWorld(stw)
  1399  	return n, ok
  1400  }
  1401  
  1402  // GoroutineProfile returns n, the number of records in the active goroutine stack profile.
  1403  // If len(p) >= n, GoroutineProfile copies the profile into p and returns n, true.
  1404  // If len(p) < n, GoroutineProfile does not change p and returns n, false.
  1405  //
  1406  // Most clients should use the [runtime/pprof] package instead
  1407  // of calling GoroutineProfile directly.
  1408  func GoroutineProfile(p []StackRecord) (n int, ok bool) {
  1409  
  1410  	return goroutineProfileWithLabels(p, nil)
  1411  }
  1412  
  1413  func saveg(pc, sp uintptr, gp *g, r *StackRecord) {
  1414  	var u unwinder
  1415  	u.initAt(pc, sp, 0, gp, unwindSilentErrors)
  1416  	n := tracebackPCs(&u, 0, r.Stack0[:])
  1417  	if n < len(r.Stack0) {
  1418  		r.Stack0[n] = 0
  1419  	}
  1420  }
  1421  
  1422  // Stack formats a stack trace of the calling goroutine into buf
  1423  // and returns the number of bytes written to buf.
  1424  // If all is true, Stack formats stack traces of all other goroutines
  1425  // into buf after the trace for the current goroutine.
  1426  func Stack(buf []byte, all bool) int {
  1427  	var stw worldStop
  1428  	if all {
  1429  		stw = stopTheWorld(stwAllGoroutinesStack)
  1430  	}
  1431  
  1432  	n := 0
  1433  	if len(buf) > 0 {
  1434  		gp := getg()
  1435  		sp := getcallersp()
  1436  		pc := getcallerpc()
  1437  		systemstack(func() {
  1438  			g0 := getg()
  1439  			// Force traceback=1 to override GOTRACEBACK setting,
  1440  			// so that Stack's results are consistent.
  1441  			// GOTRACEBACK is only about crash dumps.
  1442  			g0.m.traceback = 1
  1443  			g0.writebuf = buf[0:0:len(buf)]
  1444  			goroutineheader(gp)
  1445  			traceback(pc, sp, 0, gp)
  1446  			if all {
  1447  				tracebackothers(gp)
  1448  			}
  1449  			g0.m.traceback = 0
  1450  			n = len(g0.writebuf)
  1451  			g0.writebuf = nil
  1452  		})
  1453  	}
  1454  
  1455  	if all {
  1456  		startTheWorld(stw)
  1457  	}
  1458  	return n
  1459  }
  1460  
  1461  // Tracing of alloc/free/gc.
  1462  
  1463  var tracelock mutex
  1464  
  1465  func tracealloc(p unsafe.Pointer, size uintptr, typ *_type) {
  1466  	lock(&tracelock)
  1467  	gp := getg()
  1468  	gp.m.traceback = 2
  1469  	if typ == nil {
  1470  		print("tracealloc(", p, ", ", hex(size), ")\n")
  1471  	} else {
  1472  		print("tracealloc(", p, ", ", hex(size), ", ", toRType(typ).string(), ")\n")
  1473  	}
  1474  	if gp.m.curg == nil || gp == gp.m.curg {
  1475  		goroutineheader(gp)
  1476  		pc := getcallerpc()
  1477  		sp := getcallersp()
  1478  		systemstack(func() {
  1479  			traceback(pc, sp, 0, gp)
  1480  		})
  1481  	} else {
  1482  		goroutineheader(gp.m.curg)
  1483  		traceback(^uintptr(0), ^uintptr(0), 0, gp.m.curg)
  1484  	}
  1485  	print("\n")
  1486  	gp.m.traceback = 0
  1487  	unlock(&tracelock)
  1488  }
  1489  
  1490  func tracefree(p unsafe.Pointer, size uintptr) {
  1491  	lock(&tracelock)
  1492  	gp := getg()
  1493  	gp.m.traceback = 2
  1494  	print("tracefree(", p, ", ", hex(size), ")\n")
  1495  	goroutineheader(gp)
  1496  	pc := getcallerpc()
  1497  	sp := getcallersp()
  1498  	systemstack(func() {
  1499  		traceback(pc, sp, 0, gp)
  1500  	})
  1501  	print("\n")
  1502  	gp.m.traceback = 0
  1503  	unlock(&tracelock)
  1504  }
  1505  
  1506  func tracegc() {
  1507  	lock(&tracelock)
  1508  	gp := getg()
  1509  	gp.m.traceback = 2
  1510  	print("tracegc()\n")
  1511  	// running on m->g0 stack; show all non-g0 goroutines
  1512  	tracebackothers(gp)
  1513  	print("end tracegc\n")
  1514  	print("\n")
  1515  	gp.m.traceback = 0
  1516  	unlock(&tracelock)
  1517  }
  1518  

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