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// 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"
"internal/goarch"
"internal/profilerecord"
"internal/runtime/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
// maxSkip is to account for deferred inline expansion
// when using frame pointer unwinding. We record the stack
// with "physical" frame pointers but handle skipping "logical"
// frames at some point after collecting the stack. So
// we need extra space in order to avoid getting fewer than the
// desired maximum number of frames after expansion.
// This should be at least as large as the largest skip value
// used for profiling; otherwise stacks may be truncated inconsistently
maxSkip = 5
// maxProfStackDepth is the highest valid value for debug.profstackdepth.
// It's used for the bucket.stk func.
// TODO(fg): can we get rid of this?
maxProfStackDepth = 1024
)
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. The caller can asssume that the
// backing array is immutable.
func (b *bucket) stk() []uintptr {
stk := (*[maxProfStackDepth]uintptr)(add(unsafe.Pointer(b), unsafe.Sizeof(*b)))
if b.nstk > maxProfStackDepth {
// prove that slicing works; otherwise a failure requires a P
throw("bad profile stack count")
}
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(mp *m, p unsafe.Pointer, size uintptr) {
if mp.profStack == nil {
// mp.profStack is nil if we happen to sample an allocation during the
// initialization of mp. This case is rare, so we just ignore such
// allocations. Change MemProfileRate to 1 if you need to reproduce such
// cases for testing purposes.
return
}
// Only use the part of mp.profStack we need and ignore the extra space
// reserved for delayed inline expansion with frame pointer unwinding.
nstk := callers(4, mp.profStack[:debug.profstackdepth])
index := (mProfCycle.read() + 2) % uint32(len(memRecord{}.future))
b := stkbucket(memProfile, size, mp.profStack[:nstk], true)
mr := b.mp()
mpc := &mr.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 && cheaprand64()%rate > cycles) {
return false
}
return true
}
// saveblockevent records a profile event of the type specified by which.
// cycles is the quantity associated with this event and rate is the sampling rate,
// used to adjust the cycles value in the manner determined by the profile type.
// skip is the number of frames to omit from the traceback associated with the event.
// The traceback will be recorded from the stack of the goroutine associated with the current m.
// skip should be positive if this event is recorded from the current stack
// (e.g. when this is not called from a system stack)
func saveblockevent(cycles, rate int64, skip int, which bucketType) {
if debug.profstackdepth == 0 {
// profstackdepth is set to 0 by the user, so mp.profStack is nil and we
// can't record a stack trace.
return
}
if skip > maxSkip {
print("requested skip=", skip)
throw("invalid skip value")
}
gp := getg()
mp := acquirem() // we must not be preempted while accessing profstack
var nstk int
if tracefpunwindoff() || gp.m.hasCgoOnStack() {
if gp.m.curg == nil || gp.m.curg == gp {
nstk = callers(skip, mp.profStack)
} else {
nstk = gcallers(gp.m.curg, skip, mp.profStack)
}
} else {
if gp.m.curg == nil || gp.m.curg == gp {
if skip > 0 {
// We skip one fewer frame than the provided value for frame
// pointer unwinding because the skip value includes the current
// frame, whereas the saved frame pointer will give us the
// caller's return address first (so, not including
// saveblockevent)
skip -= 1
}
nstk = fpTracebackPartialExpand(skip, unsafe.Pointer(getfp()), mp.profStack)
} else {
mp.profStack[0] = gp.m.curg.sched.pc
nstk = 1 + fpTracebackPartialExpand(skip, unsafe.Pointer(gp.m.curg.sched.bp), mp.profStack[1:])
}
}
saveBlockEventStack(cycles, rate, mp.profStack[:nstk], which)
releasem(mp)
}
// fpTracebackPartialExpand records a call stack obtained starting from fp.
// This function will skip the given number of frames, properly accounting for
// inlining, and save remaining frames as "physical" return addresses. The
// consumer should later use CallersFrames or similar to expand inline frames.
func fpTracebackPartialExpand(skip int, fp unsafe.Pointer, pcBuf []uintptr) int {
var n int
lastFuncID := abi.FuncIDNormal
skipOrAdd := func(retPC uintptr) bool {
if skip > 0 {
skip--
} else if n < len(pcBuf) {
pcBuf[n] = retPC
n++
}
return n < len(pcBuf)
}
for n < len(pcBuf) && fp != nil {
// return addr sits one word above the frame pointer
pc := *(*uintptr)(unsafe.Pointer(uintptr(fp) + goarch.PtrSize))
if skip > 0 {
callPC := pc - 1
fi := findfunc(callPC)
u, uf := newInlineUnwinder(fi, callPC)
for ; uf.valid(); uf = u.next(uf) {
sf := u.srcFunc(uf)
if sf.funcID == abi.FuncIDWrapper && elideWrapperCalling(lastFuncID) {
// ignore wrappers
} else if more := skipOrAdd(uf.pc + 1); !more {
return n
}
lastFuncID = sf.funcID
}
} else {
// We've skipped the desired number of frames, so no need
// to perform further inline expansion now.
pcBuf[n] = pc
n++
}
// follow the frame pointer to the next one
fp = unsafe.Pointer(*(*uintptr)(fp))
}
return n
}
// lockTimer assists with profiling contention on runtime-internal locks.
//
// There are several steps between the time that an M experiences contention and
// when that contention may be added to the profile. This comes from our
// constraints: We need to keep the critical section of each lock small,
// especially when those locks are contended. The reporting code cannot acquire
// new locks until the M has released all other locks, which means no memory
// allocations and encourages use of (temporary) M-local storage.
//
// The M will have space for storing one call stack that caused contention, and
// for the magnitude of that contention. It will also have space to store the
// magnitude of additional contention the M caused, since it only has space to
// remember one call stack and might encounter several contention events before
// it releases all of its locks and is thus able to transfer the local buffer
// into the profile.
//
// The M will collect the call stack when it unlocks the contended lock. That
// minimizes the impact on the critical section of the contended lock, and
// matches the mutex profile's behavior for contention in sync.Mutex: measured
// at the Unlock method.
//
// The profile for contention on sync.Mutex blames the caller of Unlock for the
// amount of contention experienced by the callers of Lock which had to wait.
// When there are several critical sections, this allows identifying which of
// them is responsible.
//
// Matching that behavior for runtime-internal locks will require identifying
// which Ms are blocked on the mutex. The semaphore-based implementation is
// ready to allow that, but the futex-based implementation will require a bit
// more work. Until then, we report contention on runtime-internal locks with a
// call stack taken from the unlock call (like the rest of the user-space
// "mutex" profile), but assign it a duration value based on how long the
// previous lock call took (like the user-space "block" profile).
//
// Thus, reporting the call stacks of runtime-internal lock contention is
// guarded by GODEBUG for now. Set GODEBUG=runtimecontentionstacks=1 to enable.
//
// TODO(rhysh): plumb through the delay duration, remove GODEBUG, update comment
//
// The M will track this by storing a pointer to the lock; lock/unlock pairs for
// runtime-internal locks are always on the same M.
//
// Together, that demands several steps for recording contention. First, when
// finally acquiring a contended lock, the M decides whether it should plan to
// profile that event by storing a pointer to the lock in its "to be profiled
// upon unlock" field. If that field is already set, it uses the relative
// magnitudes to weight a random choice between itself and the other lock, with
// the loser's time being added to the "additional contention" field. Otherwise
// if the M's call stack buffer is occupied, it does the comparison against that
// sample's magnitude.
//
// Second, having unlocked a mutex the M checks to see if it should capture the
// call stack into its local buffer. Finally, when the M unlocks its last mutex,
// it transfers the local buffer into the profile. As part of that step, it also
// transfers any "additional contention" time to the profile. Any lock
// contention that it experiences while adding samples to the profile will be
// recorded later as "additional contention" and not include a call stack, to
// avoid an echo.
type lockTimer struct {
lock *mutex
timeRate int64
timeStart int64
tickStart int64
}
func (lt *lockTimer) begin() {
rate := int64(atomic.Load64(&mutexprofilerate))
lt.timeRate = gTrackingPeriod
if rate != 0 && rate < lt.timeRate {
lt.timeRate = rate
}
if int64(cheaprand())%lt.timeRate == 0 {
lt.timeStart = nanotime()
}
if rate > 0 && int64(cheaprand())%rate == 0 {
lt.tickStart = cputicks()
}
}
func (lt *lockTimer) end() {
gp := getg()
if lt.timeStart != 0 {
nowTime := nanotime()
gp.m.mLockProfile.waitTime.Add((nowTime - lt.timeStart) * lt.timeRate)
}
if lt.tickStart != 0 {
nowTick := cputicks()
gp.m.mLockProfile.recordLock(nowTick-lt.tickStart, lt.lock)
}
}
type mLockProfile struct {
waitTime atomic.Int64 // total nanoseconds spent waiting in runtime.lockWithRank
stack []uintptr // stack that experienced contention in runtime.lockWithRank
pending uintptr // *mutex that experienced contention (to be traceback-ed)
cycles int64 // cycles attributable to "pending" (if set), otherwise to "stack"
cyclesLost int64 // contention for which we weren't able to record a call stack
disabled bool // attribute all time to "lost"
}
func (prof *mLockProfile) recordLock(cycles int64, l *mutex) {
if cycles <= 0 {
return
}
if prof.disabled {
// We're experiencing contention while attempting to report contention.
// Make a note of its magnitude, but don't allow it to be the sole cause
// of another contention report.
prof.cyclesLost += cycles
return
}
if uintptr(unsafe.Pointer(l)) == prof.pending {
// Optimization: we'd already planned to profile this same lock (though
// possibly from a different unlock site).
prof.cycles += cycles
return
}
if prev := prof.cycles; prev > 0 {
// We can only store one call stack for runtime-internal lock contention
// on this M, and we've already got one. Decide which should stay, and
// add the other to the report for runtime._LostContendedRuntimeLock.
prevScore := uint64(cheaprand64()) % uint64(prev)
thisScore := uint64(cheaprand64()) % uint64(cycles)
if prevScore > thisScore {
prof.cyclesLost += cycles
return
} else {
prof.cyclesLost += prev
}
}
// Saving the *mutex as a uintptr is safe because:
// - lockrank_on.go does this too, which gives it regular exercise
// - the lock would only move if it's stack allocated, which means it
// cannot experience multi-M contention
prof.pending = uintptr(unsafe.Pointer(l))
prof.cycles = cycles
}
// From unlock2, we might not be holding a p in this code.
//
//go:nowritebarrierrec
func (prof *mLockProfile) recordUnlock(l *mutex) {
if uintptr(unsafe.Pointer(l)) == prof.pending {
prof.captureStack()
}
if gp := getg(); gp.m.locks == 1 && gp.m.mLockProfile.cycles != 0 {
prof.store()
}
}
func (prof *mLockProfile) captureStack() {
if debug.profstackdepth == 0 {
// profstackdepth is set to 0 by the user, so mp.profStack is nil and we
// can't record a stack trace.
return
}
skip := 3 // runtime.(*mLockProfile).recordUnlock runtime.unlock2 runtime.unlockWithRank
if staticLockRanking {
// When static lock ranking is enabled, we'll always be on the system
// stack at this point. There will be a runtime.unlockWithRank.func1
// frame, and if the call to runtime.unlock took place on a user stack
// then there'll also be a runtime.systemstack frame. To keep stack
// traces somewhat consistent whether or not static lock ranking is
// enabled, we'd like to skip those. But it's hard to tell how long
// we've been on the system stack so accept an extra frame in that case,
// with a leaf of "runtime.unlockWithRank runtime.unlock" instead of
// "runtime.unlock".
skip += 1 // runtime.unlockWithRank.func1
}
prof.pending = 0
prof.stack[0] = logicalStackSentinel
if debug.runtimeContentionStacks.Load() == 0 {
prof.stack[1] = abi.FuncPCABIInternal(_LostContendedRuntimeLock) + sys.PCQuantum
prof.stack[2] = 0
return
}
var nstk int
gp := getg()
sp := getcallersp()
pc := getcallerpc()
systemstack(func() {
var u unwinder
u.initAt(pc, sp, 0, gp, unwindSilentErrors|unwindJumpStack)
nstk = 1 + tracebackPCs(&u, skip, prof.stack[1:])
})
if nstk < len(prof.stack) {
prof.stack[nstk] = 0
}
}
func (prof *mLockProfile) store() {
// Report any contention we experience within this function as "lost"; it's
// important that the act of reporting a contention event not lead to a
// reportable contention event. This also means we can use prof.stack
// without copying, since it won't change during this function.
mp := acquirem()
prof.disabled = true
nstk := int(debug.profstackdepth)
for i := 0; i < nstk; i++ {
if pc := prof.stack[i]; pc == 0 {
nstk = i
break
}
}
cycles, lost := prof.cycles, prof.cyclesLost
prof.cycles, prof.cyclesLost = 0, 0
rate := int64(atomic.Load64(&mutexprofilerate))
saveBlockEventStack(cycles, rate, prof.stack[:nstk], mutexProfile)
if lost > 0 {
lostStk := [...]uintptr{
logicalStackSentinel,
abi.FuncPCABIInternal(_LostContendedRuntimeLock) + sys.PCQuantum,
}
saveBlockEventStack(lost, rate, lostStk[:], mutexProfile)
}
prof.disabled = false
releasem(mp)
}
func saveBlockEventStack(cycles, rate int64, stk []uintptr, which bucketType) {
b := stkbucket(which, 0, stk, 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 && cheaprand64()%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 memory profiling
// is not used and the link type guarantees nobody else could use it
// elsewhere.
// We check if the runtime.memProfileInternal symbol is present.
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) {
return memProfileInternal(len(p), inuseZero, func(r profilerecord.MemProfileRecord) {
copyMemProfileRecord(&p[0], r)
p = p[1:]
})
}
// memProfileInternal returns the number of records n in the profile. If there
// are less than size records, copyFn is invoked for each record, and ok returns
// true.
//
// The linker set disableMemoryProfiling to true to disable memory profiling
// if this function is not reachable. Mark it noinline to ensure the symbol exists.
// (This function is big and normally not inlined anyway.)
// See also disableMemoryProfiling above and cmd/link/internal/ld/lib.go:linksetup.
//
//go:noinline
func memProfileInternal(size int, inuseZero bool, copyFn func(profilerecord.MemProfileRecord)) (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 <= size {
ok = true
for b := head; b != nil; b = b.allnext {
mp := b.mp()
if inuseZero || mp.active.alloc_bytes != mp.active.free_bytes {
r := profilerecord.MemProfileRecord{
AllocBytes: int64(mp.active.alloc_bytes),
FreeBytes: int64(mp.active.free_bytes),
AllocObjects: int64(mp.active.allocs),
FreeObjects: int64(mp.active.frees),
Stack: b.stk(),
}
copyFn(r)
}
}
}
unlock(&profMemActiveLock)
return
}
func copyMemProfileRecord(dst *MemProfileRecord, src profilerecord.MemProfileRecord) {
dst.AllocBytes = src.AllocBytes
dst.FreeBytes = src.FreeBytes
dst.AllocObjects = src.AllocObjects
dst.FreeObjects = src.FreeObjects
if raceenabled {
racewriterangepc(unsafe.Pointer(&dst.Stack0[0]), unsafe.Sizeof(dst.Stack0), getcallerpc(), abi.FuncPCABIInternal(MemProfile))
}
if msanenabled {
msanwrite(unsafe.Pointer(&dst.Stack0[0]), unsafe.Sizeof(dst.Stack0))
}
if asanenabled {
asanwrite(unsafe.Pointer(&dst.Stack0[0]), unsafe.Sizeof(dst.Stack0))
}
i := copy(dst.Stack0[:], src.Stack)
clear(dst.Stack0[i:])
}
//go:linkname pprof_memProfileInternal
func pprof_memProfileInternal(p []profilerecord.MemProfileRecord, inuseZero bool) (n int, ok bool) {
return memProfileInternal(len(p), inuseZero, func(r profilerecord.MemProfileRecord) {
p[0] = r
p = p[1:]
})
}
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) {
var m int
n, ok = blockProfileInternal(len(p), func(r profilerecord.BlockProfileRecord) {
copyBlockProfileRecord(&p[m], r)
m++
})
if ok {
expandFrames(p[:n])
}
return
}
func expandFrames(p []BlockProfileRecord) {
expandedStack := makeProfStack()
for i := range p {
cf := CallersFrames(p[i].Stack())
j := 0
for ; j < len(expandedStack); j++ {
f, more := cf.Next()
// f.PC is a "call PC", but later consumers will expect
// "return PCs"
expandedStack[j] = f.PC + 1
if !more {
break
}
}
k := copy(p[i].Stack0[:], expandedStack[:j])
clear(p[i].Stack0[k:])
}
}
// blockProfileInternal returns the number of records n in the profile. If there
// are less than size records, copyFn is invoked for each record, and ok returns
// true.
func blockProfileInternal(size int, copyFn func(profilerecord.BlockProfileRecord)) (n int, ok bool) {
lock(&profBlockLock)
head := (*bucket)(bbuckets.Load())
for b := head; b != nil; b = b.allnext {
n++
}
if n <= size {
ok = true
for b := head; b != nil; b = b.allnext {
bp := b.bp()
r := profilerecord.BlockProfileRecord{
Count: int64(bp.count),
Cycles: bp.cycles,
Stack: b.stk(),
}
// 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
}
copyFn(r)
}
}
unlock(&profBlockLock)
return
}
// copyBlockProfileRecord copies the sample values and call stack from src to dst.
// The call stack is copied as-is. The caller is responsible for handling inline
// expansion, needed when the call stack was collected with frame pointer unwinding.
func copyBlockProfileRecord(dst *BlockProfileRecord, src profilerecord.BlockProfileRecord) {
dst.Count = src.Count
dst.Cycles = src.Cycles
if raceenabled {
racewriterangepc(unsafe.Pointer(&dst.Stack0[0]), unsafe.Sizeof(dst.Stack0), getcallerpc(), abi.FuncPCABIInternal(BlockProfile))
}
if msanenabled {
msanwrite(unsafe.Pointer(&dst.Stack0[0]), unsafe.Sizeof(dst.Stack0))
}
if asanenabled {
asanwrite(unsafe.Pointer(&dst.Stack0[0]), unsafe.Sizeof(dst.Stack0))
}
// We just copy the stack here without inline expansion
// (needed if frame pointer unwinding is used)
// since this function is called under the profile lock,
// and doing something that might allocate can violate lock ordering.
i := copy(dst.Stack0[:], src.Stack)
clear(dst.Stack0[i:])
}
//go:linkname pprof_blockProfileInternal
func pprof_blockProfileInternal(p []profilerecord.BlockProfileRecord) (n int, ok bool) {
return blockProfileInternal(len(p), func(r profilerecord.BlockProfileRecord) {
p[0] = r
p = p[1:]
})
}
// 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) {
var m int
n, ok = mutexProfileInternal(len(p), func(r profilerecord.BlockProfileRecord) {
copyBlockProfileRecord(&p[m], r)
m++
})
if ok {
expandFrames(p[:n])
}
return
}
// mutexProfileInternal returns the number of records n in the profile. If there
// are less than size records, copyFn is invoked for each record, and ok returns
// true.
func mutexProfileInternal(size int, copyFn func(profilerecord.BlockProfileRecord)) (n int, ok bool) {
lock(&profBlockLock)
head := (*bucket)(xbuckets.Load())
for b := head; b != nil; b = b.allnext {
n++
}
if n <= size {
ok = true
for b := head; b != nil; b = b.allnext {
bp := b.bp()
r := profilerecord.BlockProfileRecord{
Count: int64(bp.count),
Cycles: bp.cycles,
Stack: b.stk(),
}
copyFn(r)
}
}
unlock(&profBlockLock)
return
}
//go:linkname pprof_mutexProfileInternal
func pprof_mutexProfileInternal(p []profilerecord.BlockProfileRecord) (n int, ok bool) {
return mutexProfileInternal(len(p), func(r profilerecord.BlockProfileRecord) {
p[0] = r
p = p[1:]
})
}
// 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) {
return threadCreateProfileInternal(len(p), func(r profilerecord.StackRecord) {
copy(p[0].Stack0[:], r.Stack)
p = p[1:]
})
}
// threadCreateProfileInternal returns the number of records n in the profile.
// If there are less than size records, copyFn is invoked for each record, and
// ok returns true.
func threadCreateProfileInternal(size int, copyFn func(profilerecord.StackRecord)) (n int, ok bool) {
first := (*m)(atomic.Loadp(unsafe.Pointer(&allm)))
for mp := first; mp != nil; mp = mp.alllink {
n++
}
if n <= size {
ok = true
for mp := first; mp != nil; mp = mp.alllink {
r := profilerecord.StackRecord{Stack: mp.createstack[:]}
copyFn(r)
}
}
return
}
//go:linkname pprof_threadCreateInternal
func pprof_threadCreateInternal(p []profilerecord.StackRecord) (n int, ok bool) {
return threadCreateProfileInternal(len(p), func(r profilerecord.StackRecord) {
p[0] = r
p = p[1:]
})
}
//go:linkname pprof_goroutineProfileWithLabels
func pprof_goroutineProfileWithLabels(p []profilerecord.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 []profilerecord.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 []profilerecord.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 []profilerecord.StackRecord, labels []unsafe.Pointer) (n int, ok bool) {
if len(p) == 0 {
// An empty slice is obviously too small. Return a rough
// allocation estimate without bothering to STW. As long as
// this is close, then we'll only need to STW once (on the next
// call).
return int(gcount()), false
}
semacquire(&goroutineProfile.sema)
ourg := getg()
pcbuf := makeProfStack() // see saveg() for explanation
stw := 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(stw)
semrelease(&goroutineProfile.sema)
return n, false
}
// Save current goroutine.
sp := getcallersp()
pc := getcallerpc()
systemstack(func() {
saveg(pc, sp, ourg, &p[0], pcbuf)
})
if labels != nil {
labels[0] = ourg.labels
}
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, pcbuf)
}
}
startTheWorld(stw)
// 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, pcbuf, Gosched)
})
stw = stopTheWorld(stwGoroutineProfileCleanup)
endOffset := goroutineProfile.offset.Swap(0)
goroutineProfile.active = false
goroutineProfile.records = nil
goroutineProfile.labels = nil
startTheWorld(stw)
// 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, nil, 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, pcbuf []uintptr, 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, pcbuf)
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, pcbuf []uintptr) {
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], pcbuf) })
if goroutineProfile.labels != nil {
goroutineProfile.labels[offset] = gp1.labels
}
}
func goroutineProfileWithLabelsSync(p []profilerecord.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)
}
pcbuf := makeProfStack() // see saveg() for explanation
stw := 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], pcbuf)
})
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], pcbuf) })
if labels != nil {
lbl[0] = gp1.labels
lbl = lbl[1:]
}
r = r[1:]
})
}
if raceenabled {
raceacquire(unsafe.Pointer(&labelSync))
}
startTheWorld(stw)
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) {
records := make([]profilerecord.StackRecord, len(p))
n, ok = goroutineProfileInternal(records)
if !ok {
return
}
for i, mr := range records[0:n] {
copy(p[i].Stack0[:], mr.Stack)
}
return
}
func goroutineProfileInternal(p []profilerecord.StackRecord) (n int, ok bool) {
return goroutineProfileWithLabels(p, nil)
}
func saveg(pc, sp uintptr, gp *g, r *profilerecord.StackRecord, pcbuf []uintptr) {
// To reduce memory usage, we want to allocate a r.Stack that is just big
// enough to hold gp's stack trace. Naively we might achieve this by
// recording our stack trace into mp.profStack, and then allocating a
// r.Stack of the right size. However, mp.profStack is also used for
// allocation profiling, so it could get overwritten if the slice allocation
// gets profiled. So instead we record the stack trace into a temporary
// pcbuf which is usually given to us by our caller. When it's not, we have
// to allocate one here. This will only happen for goroutines that were in a
// syscall when the goroutine profile started or for goroutines that manage
// to execute before we finish iterating over all the goroutines.
if pcbuf == nil {
pcbuf = makeProfStack()
}
var u unwinder
u.initAt(pc, sp, 0, gp, unwindSilentErrors)
n := tracebackPCs(&u, 0, pcbuf)
r.Stack = make([]uintptr, n)
copy(r.Stack, pcbuf)
}
// 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 {
var stw worldStop
if all {
stw = 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(stw)
}
return n
}