src/runtime/cpuprof.go - go - Git at Google

 // Copyright 2011 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.

 // CPU profiling.
 //
 // The signal handler for the profiling clock tick adds a new stack trace
 // to a log of recent traces. The log is read by a user goroutine that
 // turns it into formatted profile data. If the reader does not keep up
 // with the log, those writes will be recorded as a count of lost records.
 // The actual profile buffer is in profbuf.go.

 package runtime

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

 const (
 	maxCPUProfStack = 64

 	// profBufWordCount is the size of the CPU profile buffer's storage for the
 	// header and stack of each sample, measured in 64-bit words. Every sample
 	// has a required header of two words. With a small additional header (a
 	// word or two) and stacks at the profiler's maximum length of 64 frames,
 	// that capacity can support 1900 samples or 19 thread-seconds at a 100 Hz
 	// sample rate, at a cost of 1 MiB.
 	profBufWordCount = 1 << 17
 	// profBufTagCount is the size of the CPU profile buffer's storage for the
 	// goroutine tags associated with each sample. A capacity of 1<<14 means
 	// room for 16k samples, or 160 thread-seconds at a 100 Hz sample rate.
 	profBufTagCount = 1 << 14
 )

 type cpuProfile struct {
 	lock mutex
 	on   bool     // profiling is on
 	log  *profBuf // profile events written here

 	// extra holds extra stacks accumulated in addNonGo
 	// corresponding to profiling signals arriving on
 	// non-Go-created threads. Those stacks are written
 	// to log the next time a normal Go thread gets the
 	// signal handler.
 	// Assuming the stacks are 2 words each (we don't get
 	// a full traceback from those threads), plus one word
 	// size for framing, 100 Hz profiling would generate
 	// 300 words per second.
 	// Hopefully a normal Go thread will get the profiling
 	// signal at least once every few seconds.
 	extra      [1000]uintptr
 	numExtra   int
 	lostExtra  uint64 // count of frames lost because extra is full
 	lostAtomic uint64 // count of frames lost because of being in atomic64 on mips/arm; updated racily
 }

 var cpuprof cpuProfile

 // SetCPUProfileRate sets the CPU profiling rate to hz samples per second.
 // If hz <= 0, SetCPUProfileRate turns off profiling.
 // If the profiler is on, the rate cannot be changed without first turning it off.
 //
 // Most clients should use the [runtime/pprof] package or
 // the [testing] package's -test.cpuprofile flag instead of calling
 // SetCPUProfileRate directly.
 func SetCPUProfileRate(hz int) {
 	// Clamp hz to something reasonable.
 	if hz < 0 {
 		hz = 0
 	}
 	if hz > 1000000 {
 		hz = 1000000
 	}

 	lock(&cpuprof.lock)
 	if hz > 0 {
 		if cpuprof.on || cpuprof.log != nil {
 			print("runtime: cannot set cpu profile rate until previous profile has finished.\n")
 			unlock(&cpuprof.lock)
 			return
 		}

 		cpuprof.on = true
 		cpuprof.log = newProfBuf(1, profBufWordCount, profBufTagCount)
 		hdr := [1]uint64{uint64(hz)}
 		cpuprof.log.write(nil, nanotime(), hdr[:], nil)
 		setcpuprofilerate(int32(hz))
 	} else if cpuprof.on {
 		setcpuprofilerate(0)
 		cpuprof.on = false
 		cpuprof.addExtra()
 		cpuprof.log.close()
 	}
 	unlock(&cpuprof.lock)
 }

 // add adds the stack trace to the profile.
 // It is called from signal handlers and other limited environments
 // and cannot allocate memory or acquire locks that might be
 // held at the time of the signal, nor can it use substantial amounts
 // of stack.
 //
 //go:nowritebarrierrec
 func (p *cpuProfile) add(tagPtr *unsafe.Pointer, stk []uintptr) {
 	// Simple cas-lock to coordinate with setcpuprofilerate.
 	for !prof.signalLock.CompareAndSwap(0, 1) {
 		// TODO: Is it safe to osyield here? https://go.dev/issue/52672
 		osyield()
 	}

 	if prof.hz.Load() != 0 { // implies cpuprof.log != nil
 		if p.numExtra > 0 || p.lostExtra > 0 || p.lostAtomic > 0 {
 			p.addExtra()
 		}
 		hdr := [1]uint64{1}
 		// Note: write "knows" that the argument is &gp.labels,
 		// because otherwise its write barrier behavior may not
 		// be correct. See the long comment there before
 		// changing the argument here.
 		cpuprof.log.write(tagPtr, nanotime(), hdr[:], stk)
 	}

 	prof.signalLock.Store(0)
 }

 // addNonGo adds the non-Go stack trace to the profile.
 // It is called from a non-Go thread, so we cannot use much stack at all,
 // nor do anything that needs a g or an m.
 // In particular, we can't call cpuprof.log.write.
 // Instead, we copy the stack into cpuprof.extra,
 // which will be drained the next time a Go thread
 // gets the signal handling event.
 //
 //go:nosplit
 //go:nowritebarrierrec
 func (p *cpuProfile) addNonGo(stk []uintptr) {
 	// Simple cas-lock to coordinate with SetCPUProfileRate.
 	// (Other calls to add or addNonGo should be blocked out
 	// by the fact that only one SIGPROF can be handled by the
 	// process at a time. If not, this lock will serialize those too.
 	// The use of timer_create(2) on Linux to request process-targeted
 	// signals may have changed this.)
 	for !prof.signalLock.CompareAndSwap(0, 1) {
 		// TODO: Is it safe to osyield here? https://go.dev/issue/52672
 		osyield()
 	}

 	if cpuprof.numExtra+1+len(stk) < len(cpuprof.extra) {
 		i := cpuprof.numExtra
 		cpuprof.extra[i] = uintptr(1 + len(stk))
 		copy(cpuprof.extra[i+1:], stk)
 		cpuprof.numExtra += 1 + len(stk)
 	} else {
 		cpuprof.lostExtra++
 	}

 	prof.signalLock.Store(0)
 }

 // addExtra adds the "extra" profiling events,
 // queued by addNonGo, to the profile log.
 // addExtra is called either from a signal handler on a Go thread
 // or from an ordinary goroutine; either way it can use stack
 // and has a g. The world may be stopped, though.
 func (p *cpuProfile) addExtra() {
 	// Copy accumulated non-Go profile events.
 	hdr := [1]uint64{1}
 	for i := 0; i < p.numExtra; {
 		p.log.write(nil, 0, hdr[:], p.extra[i+1:i+int(p.extra[i])])
 		i += int(p.extra[i])
 	}
 	p.numExtra = 0

 	// Report any lost events.
 	if p.lostExtra > 0 {
 		hdr := [1]uint64{p.lostExtra}
 		lostStk := [2]uintptr{
 			abi.FuncPCABIInternal(_LostExternalCode) + sys.PCQuantum,
 			abi.FuncPCABIInternal(_ExternalCode) + sys.PCQuantum,
 		}
 		p.log.write(nil, 0, hdr[:], lostStk[:])
 		p.lostExtra = 0
 	}

 	if p.lostAtomic > 0 {
 		hdr := [1]uint64{p.lostAtomic}
 		lostStk := [2]uintptr{
 			abi.FuncPCABIInternal(_LostSIGPROFDuringAtomic64) + sys.PCQuantum,
 			abi.FuncPCABIInternal(_System) + sys.PCQuantum,
 		}
 		p.log.write(nil, 0, hdr[:], lostStk[:])
 		p.lostAtomic = 0
 	}

 }

 // CPUProfile panics.
 // It formerly provided raw access to chunks of
 // a pprof-format profile generated by the runtime.
 // The details of generating that format have changed,
 // so this functionality has been removed.
 //
 // Deprecated: Use the [runtime/pprof] package,
 // or the handlers in the [net/http/pprof] package,
 // or the [testing] package's -test.cpuprofile flag instead.
 func CPUProfile() []byte {
 	panic("CPUProfile no longer available")
 }

 // runtime/pprof.runtime_cyclesPerSecond should be an internal detail,
 // but widely used packages access it using linkname.
 // Notable members of the hall of shame include:
 //   - github.com/grafana/pyroscope-go/godeltaprof
 //   - github.com/pyroscope-io/godeltaprof
 //
 // Do not remove or change the type signature.
 // See go.dev/issue/67401.
 //
 //go:linkname pprof_cyclesPerSecond runtime/pprof.runtime_cyclesPerSecond
 func pprof_cyclesPerSecond() int64 {
 	return ticksPerSecond()
 }

 // readProfile, provided to runtime/pprof, returns the next chunk of
 // binary CPU profiling stack trace data, blocking until data is available.
 // If profiling is turned off and all the profile data accumulated while it was
 // on has been returned, readProfile returns eof=true.
 // The caller must save the returned data and tags before calling readProfile again.
 // The returned data contains a whole number of records, and tags contains
 // exactly one entry per record.
 //
 // runtime_pprof_readProfile should be an internal detail,
 // but widely used packages access it using linkname.
 // Notable members of the hall of shame include:
 //   - github.com/pyroscope-io/pyroscope
 //
 // Do not remove or change the type signature.
 // See go.dev/issue/67401.
 //
 //go:linkname runtime_pprof_readProfile runtime/pprof.readProfile
 func runtime_pprof_readProfile() ([]uint64, []unsafe.Pointer, bool) {
 	lock(&cpuprof.lock)
 	log := cpuprof.log
 	unlock(&cpuprof.lock)
 	readMode := profBufBlocking
 	if GOOS == "darwin" || GOOS == "ios" {
 		readMode = profBufNonBlocking // For #61768; on Darwin notes are not async-signal-safe.  See sigNoteSetup in os_darwin.go.
 	}
 	data, tags, eof := log.read(readMode)
 	if len(data) == 0 && eof {
 		lock(&cpuprof.lock)
 		cpuprof.log = nil
 		unlock(&cpuprof.lock)
 	}
 	return data, tags, eof
 }
	// Copyright 2011 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.

	// CPU profiling.
	//
	// The signal handler for the profiling clock tick adds a new stack trace
	// to a log of recent traces. The log is read by a user goroutine that
	// turns it into formatted profile data. If the reader does not keep up
	// with the log, those writes will be recorded as a count of lost records.
	// The actual profile buffer is in profbuf.go.

	package runtime

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

	const (
	maxCPUProfStack = 64

	// profBufWordCount is the size of the CPU profile buffer's storage for the
	// header and stack of each sample, measured in 64-bit words. Every sample
	// has a required header of two words. With a small additional header (a
	// word or two) and stacks at the profiler's maximum length of 64 frames,
	// that capacity can support 1900 samples or 19 thread-seconds at a 100 Hz
	// sample rate, at a cost of 1 MiB.
	profBufWordCount = 1 << 17
	// profBufTagCount is the size of the CPU profile buffer's storage for the
	// goroutine tags associated with each sample. A capacity of 1<<14 means
	// room for 16k samples, or 160 thread-seconds at a 100 Hz sample rate.
	profBufTagCount = 1 << 14
	)

	type cpuProfile struct {
	lock mutex
	on bool // profiling is on
	log *profBuf // profile events written here

	// extra holds extra stacks accumulated in addNonGo
	// corresponding to profiling signals arriving on
	// non-Go-created threads. Those stacks are written
	// to log the next time a normal Go thread gets the
	// signal handler.
	// Assuming the stacks are 2 words each (we don't get
	// a full traceback from those threads), plus one word
	// size for framing, 100 Hz profiling would generate
	// 300 words per second.
	// Hopefully a normal Go thread will get the profiling
	// signal at least once every few seconds.
	extra [1000]uintptr
	numExtra int
	lostExtra uint64 // count of frames lost because extra is full
	lostAtomic uint64 // count of frames lost because of being in atomic64 on mips/arm; updated racily
	}

	var cpuprof cpuProfile

	// SetCPUProfileRate sets the CPU profiling rate to hz samples per second.
	// If hz <= 0, SetCPUProfileRate turns off profiling.
	// If the profiler is on, the rate cannot be changed without first turning it off.
	//
	// Most clients should use the [runtime/pprof] package or
	// the [testing] package's -test.cpuprofile flag instead of calling
	// SetCPUProfileRate directly.
	func SetCPUProfileRate(hz int) {
	// Clamp hz to something reasonable.
	if hz < 0 {
	hz = 0
	}
	if hz > 1000000 {
	hz = 1000000
	}

	lock(&cpuprof.lock)
	if hz > 0 {
	if cpuprof.on \|\| cpuprof.log != nil {
	print("runtime: cannot set cpu profile rate until previous profile has finished.\n")
	unlock(&cpuprof.lock)
	return
	}

	cpuprof.on = true
	cpuprof.log = newProfBuf(1, profBufWordCount, profBufTagCount)
	hdr := [1]uint64{uint64(hz)}
	cpuprof.log.write(nil, nanotime(), hdr[:], nil)
	setcpuprofilerate(int32(hz))
	} else if cpuprof.on {
	setcpuprofilerate(0)
	cpuprof.on = false
	cpuprof.addExtra()
	cpuprof.log.close()
	}
	unlock(&cpuprof.lock)
	}

	// add adds the stack trace to the profile.
	// It is called from signal handlers and other limited environments
	// and cannot allocate memory or acquire locks that might be
	// held at the time of the signal, nor can it use substantial amounts
	// of stack.
	//
	//go:nowritebarrierrec
	func (p cpuProfile) add(tagPtr unsafe.Pointer, stk []uintptr) {
	// Simple cas-lock to coordinate with setcpuprofilerate.
	for !prof.signalLock.CompareAndSwap(0, 1) {
	// TODO: Is it safe to osyield here? https://go.dev/issue/52672
	osyield()
	}

	if prof.hz.Load() != 0 { // implies cpuprof.log != nil
	if p.numExtra > 0 \|\| p.lostExtra > 0 \|\| p.lostAtomic > 0 {
	p.addExtra()
	}
	hdr := [1]uint64{1}
	// Note: write "knows" that the argument is &gp.labels,
	// because otherwise its write barrier behavior may not
	// be correct. See the long comment there before
	// changing the argument here.
	cpuprof.log.write(tagPtr, nanotime(), hdr[:], stk)
	}

	prof.signalLock.Store(0)
	}

	// addNonGo adds the non-Go stack trace to the profile.
	// It is called from a non-Go thread, so we cannot use much stack at all,
	// nor do anything that needs a g or an m.
	// In particular, we can't call cpuprof.log.write.
	// Instead, we copy the stack into cpuprof.extra,
	// which will be drained the next time a Go thread
	// gets the signal handling event.
	//
	//go:nosplit
	//go:nowritebarrierrec
	func (p *cpuProfile) addNonGo(stk []uintptr) {
	// Simple cas-lock to coordinate with SetCPUProfileRate.
	// (Other calls to add or addNonGo should be blocked out
	// by the fact that only one SIGPROF can be handled by the
	// process at a time. If not, this lock will serialize those too.
	// The use of timer_create(2) on Linux to request process-targeted
	// signals may have changed this.)
	for !prof.signalLock.CompareAndSwap(0, 1) {
	// TODO: Is it safe to osyield here? https://go.dev/issue/52672
	osyield()
	}

	if cpuprof.numExtra+1+len(stk) < len(cpuprof.extra) {
	i := cpuprof.numExtra
	cpuprof.extra[i] = uintptr(1 + len(stk))
	copy(cpuprof.extra[i+1:], stk)
	cpuprof.numExtra += 1 + len(stk)
	} else {
	cpuprof.lostExtra++
	}

	prof.signalLock.Store(0)
	}

	// addExtra adds the "extra" profiling events,
	// queued by addNonGo, to the profile log.
	// addExtra is called either from a signal handler on a Go thread
	// or from an ordinary goroutine; either way it can use stack
	// and has a g. The world may be stopped, though.
	func (p *cpuProfile) addExtra() {
	// Copy accumulated non-Go profile events.
	hdr := [1]uint64{1}
	for i := 0; i < p.numExtra; {
	p.log.write(nil, 0, hdr[:], p.extra[i+1:i+int(p.extra[i])])
	i += int(p.extra[i])
	}
	p.numExtra = 0

	// Report any lost events.
	if p.lostExtra > 0 {
	hdr := [1]uint64{p.lostExtra}
	lostStk := [2]uintptr{
	abi.FuncPCABIInternal(_LostExternalCode) + sys.PCQuantum,
	abi.FuncPCABIInternal(_ExternalCode) + sys.PCQuantum,
	}
	p.log.write(nil, 0, hdr[:], lostStk[:])
	p.lostExtra = 0
	}

	if p.lostAtomic > 0 {
	hdr := [1]uint64{p.lostAtomic}
	lostStk := [2]uintptr{
	abi.FuncPCABIInternal(_LostSIGPROFDuringAtomic64) + sys.PCQuantum,
	abi.FuncPCABIInternal(_System) + sys.PCQuantum,
	}
	p.log.write(nil, 0, hdr[:], lostStk[:])
	p.lostAtomic = 0
	}

	}

	// CPUProfile panics.
	// It formerly provided raw access to chunks of
	// a pprof-format profile generated by the runtime.
	// The details of generating that format have changed,
	// so this functionality has been removed.
	//
	// Deprecated: Use the [runtime/pprof] package,
	// or the handlers in the [net/http/pprof] package,
	// or the [testing] package's -test.cpuprofile flag instead.
	func CPUProfile() []byte {
	panic("CPUProfile no longer available")
	}

	// runtime/pprof.runtime_cyclesPerSecond should be an internal detail,
	// but widely used packages access it using linkname.
	// Notable members of the hall of shame include:
	// - github.com/grafana/pyroscope-go/godeltaprof
	// - github.com/pyroscope-io/godeltaprof
	//
	// Do not remove or change the type signature.
	// See go.dev/issue/67401.
	//
	//go:linkname pprof_cyclesPerSecond runtime/pprof.runtime_cyclesPerSecond
	func pprof_cyclesPerSecond() int64 {
	return ticksPerSecond()
	}

	// readProfile, provided to runtime/pprof, returns the next chunk of
	// binary CPU profiling stack trace data, blocking until data is available.
	// If profiling is turned off and all the profile data accumulated while it was
	// on has been returned, readProfile returns eof=true.
	// The caller must save the returned data and tags before calling readProfile again.
	// The returned data contains a whole number of records, and tags contains
	// exactly one entry per record.
	//
	// runtime_pprof_readProfile should be an internal detail,
	// but widely used packages access it using linkname.
	// Notable members of the hall of shame include:
	// - github.com/pyroscope-io/pyroscope
	//
	// Do not remove or change the type signature.
	// See go.dev/issue/67401.
	//
	//go:linkname runtime_pprof_readProfile runtime/pprof.readProfile
	func runtime_pprof_readProfile() ([]uint64, []unsafe.Pointer, bool) {
	lock(&cpuprof.lock)
	log := cpuprof.log
	unlock(&cpuprof.lock)
	readMode := profBufBlocking
	if GOOS == "darwin" \|\| GOOS == "ios" {
	readMode = profBufNonBlocking // For #61768; on Darwin notes are not async-signal-safe. See sigNoteSetup in os_darwin.go.
	}
	data, tags, eof := log.read(readMode)
	if len(data) == 0 && eof {
	lock(&cpuprof.lock)
	cpuprof.log = nil
	unlock(&cpuprof.lock)
	}
	return data, tags, eof
	}