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runtime: convert cpuprof from C to Go

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https://golang.org/cl/132440043
This commit is contained in:
Matthew Dempsky 2014-09-02 00:14:22 -04:00 committed by Russ Cox
parent a19e638db2
commit ac49e6735b
5 changed files with 431 additions and 464 deletions
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424
src/pkg/runtime/cpuprof.go Normal file
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@ -0,0 +1,424 @@
// 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.
// Based on algorithms and data structures used in
// http://code.google.com/p/google-perftools/.
//
// The main difference between this code and the google-perftools
// code is that this code is written to allow copying the profile data
// to an arbitrary io.Writer, while the google-perftools code always
// writes to an operating system file.
//
// The signal handler for the profiling clock tick adds a new stack trace
// to a hash table tracking counts for recent traces. Most clock ticks
// hit in the cache. In the event of a cache miss, an entry must be
// evicted from the hash table, copied to a log that will eventually be
// written as profile data. The google-perftools code flushed the
// log itself during the signal handler. This code cannot do that, because
// the io.Writer might block or need system calls or locks that are not
// safe to use from within the signal handler. Instead, we split the log
// into two halves and let the signal handler fill one half while a goroutine
// is writing out the other half. When the signal handler fills its half, it
// offers to swap with the goroutine. If the writer is not done with its half,
// we lose the stack trace for this clock tick (and record that loss).
// The goroutine interacts with the signal handler by calling getprofile() to
// get the next log piece to write, implicitly handing back the last log
// piece it obtained.
//
// The state of this dance between the signal handler and the goroutine
// is encoded in the Profile.handoff field. If handoff == 0, then the goroutine
// is not using either log half and is waiting (or will soon be waiting) for
// a new piece by calling notesleep(&p->wait). If the signal handler
// changes handoff from 0 to non-zero, it must call notewakeup(&p->wait)
// to wake the goroutine. The value indicates the number of entries in the
// log half being handed off. The goroutine leaves the non-zero value in
// place until it has finished processing the log half and then flips the number
// back to zero. Setting the high bit in handoff means that the profiling is over,
// and the goroutine is now in charge of flushing the data left in the hash table
// to the log and returning that data.
//
// The handoff field is manipulated using atomic operations.
// For the most part, the manipulation of handoff is orderly: if handoff == 0
// then the signal handler owns it and can change it to non-zero.
// If handoff != 0 then the goroutine owns it and can change it to zero.
// If that were the end of the story then we would not need to manipulate
// handoff using atomic operations. The operations are needed, however,
// in order to let the log closer set the high bit to indicate "EOF" safely
// in the situation when normally the goroutine "owns" handoff.
package runtime
import "unsafe"
const (
numBuckets = 1 << 10
logSize = 1 << 17
assoc = 4
maxCPUProfStack = 64
)
type cpuprofEntry struct {
count uintptr
depth uintptr
stack [maxCPUProfStack]uintptr
}
type cpuProfile struct {
on bool // profiling is on
wait note // goroutine waits here
count uintptr // tick count
evicts uintptr // eviction count
lost uintptr // lost ticks that need to be logged
// Active recent stack traces.
hash [numBuckets]struct {
entry [assoc]cpuprofEntry
}
// Log of traces evicted from hash.
// Signal handler has filled log[toggle][:nlog].
// Goroutine is writing log[1-toggle][:handoff].
log [2][logSize / 2]uintptr
nlog uintptr
toggle int32
handoff uint32
// Writer state.
// Writer maintains its own toggle to avoid races
// looking at signal handler's toggle.
wtoggle uint32
wholding bool // holding & need to release a log half
flushing bool // flushing hash table - profile is over
eodSent bool // special end-of-data record sent; => flushing
}
var (
cpuprofLock mutex
cpuprof *cpuProfile
eod = [3]uintptr{0, 1, 0}
)
func setcpuprofilerate(int32) // proc.c
// lostProfileData is a no-op function used in profiles
// to mark the number of profiling stack traces that were
// discarded due to slow data writers.
func lostProfileData() {}
// 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(&cpuprofLock)
if hz > 0 {
if cpuprof == nil {
cpuprof = (*cpuProfile)(sysAlloc(unsafe.Sizeof(cpuProfile{}), &memstats.other_sys))
if cpuprof == nil {
print("runtime: cpu profiling cannot allocate memory\n")
unlock(&cpuprofLock)
return
}
}
if cpuprof.on || cpuprof.handoff != 0 {
print("runtime: cannot set cpu profile rate until previous profile has finished.\n")
unlock(&cpuprofLock)
return
}
cpuprof.on = true
// pprof binary header format.
// http://code.google.com/p/google-perftools/source/browse/trunk/src/profiledata.cc#117
p := &cpuprof.log[0]
p[0] = 0 // count for header
p[1] = 3 // depth for header
p[2] = 0 // version number
p[3] = uintptr(1e6 / hz) // period (microseconds)
p[4] = 0
cpuprof.nlog = 5
cpuprof.toggle = 0
cpuprof.wholding = false
cpuprof.wtoggle = 0
cpuprof.flushing = false
cpuprof.eodSent = false
noteclear(&cpuprof.wait)
setcpuprofilerate(int32(hz))
} else if cpuprof != nil && cpuprof.on {
setcpuprofilerate(0)
cpuprof.on = false
// Now add is not running anymore, and getprofile owns the entire log.
// Set the high bit in prof->handoff to tell getprofile.
for {
n := cpuprof.handoff
if n&0x80000000 != 0 {
print("runtime: setcpuprofile(off) twice\n")
}
if cas(&cpuprof.handoff, n, n|0x80000000) {
if n == 0 {
// we did the transition from 0 -> nonzero so we wake getprofile
notewakeup(&cpuprof.wait)
}
break
}
}
}
unlock(&cpuprofLock)
}
func cpuproftick(pc *uintptr, n int32) {
if n > maxCPUProfStack {
n = maxCPUProfStack
}
s := (*[maxCPUProfStack]uintptr)(unsafe.Pointer(pc))[:n]
cpuprof.add(s)
}
// 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. It is allowed to call evict.
func (p *cpuProfile) add(pc []uintptr) {
// Compute hash.
h := uintptr(0)
for _, x := range pc {
h = h<<8 | (h >> (8 * (unsafe.Sizeof(h) - 1)))
h += x*31 + x*7 + x*3
}
p.count++
// Add to entry count if already present in table.
b := &p.hash[h%numBuckets]
Assoc:
for i := range b.entry {
e := &b.entry[i]
if e.depth != uintptr(len(pc)) {
continue
}
for j := range pc {
if e.stack[j] != pc[j] {
continue Assoc
}
}
e.count++
return
}
// Evict entry with smallest count.
var e *cpuprofEntry
for i := range b.entry {
if e == nil || b.entry[i].count < e.count {
e = &b.entry[i]
}
}
if e.count > 0 {
if !p.evict(e) {
// Could not evict entry. Record lost stack.
p.lost++
return
}
p.evicts++
}
// Reuse the newly evicted entry.
e.depth = uintptr(len(pc))
e.count = 1
for i := range pc {
e.stack[i] = pc[i]
}
}
// evict copies the given entry's data into the log, so that
// the entry can be reused. evict is called from add, which
// is called from the profiling signal handler, so it must not
// allocate memory or block. It is safe to call flushlog.
// evict returns true if the entry was copied to the log,
// false if there was no room available.
func (p *cpuProfile) evict(e *cpuprofEntry) bool {
d := e.depth
nslot := d + 2
log := &p.log[p.toggle]
if p.nlog+nslot > uintptr(len(p.log[0])) {
if !p.flushlog() {
return false
}
log = &p.log[p.toggle]
}
q := p.nlog
log[q] = e.count
q++
log[q] = d
q++
for i := uintptr(0); i < d; i++ {
log[q] = e.stack[i]
q++
}
p.nlog = q
e.count = 0
return true
}
// flushlog tries to flush the current log and switch to the other one.
// flushlog is called from evict, called from add, called from the signal handler,
// so it cannot allocate memory or block. It can try to swap logs with
// the writing goroutine, as explained in the comment at the top of this file.
func (p *cpuProfile) flushlog() bool {
if !cas(&p.handoff, 0, uint32(p.nlog)) {
return false
}
notewakeup(&p.wait)
p.toggle = 1 - p.toggle
log := &p.log[p.toggle]
q := uintptr(0)
if p.lost > 0 {
f := lostProfileData
lostPC := **(**uintptr)(unsafe.Pointer(&f))
log[0] = p.lost
log[1] = 1
log[2] = lostPC
q = 3
p.lost = 0
}
p.nlog = q
return true
}
// getprofile blocks until the next block of profiling data is available
// and returns it as a []byte. It is called from the writing goroutine.
func (p *cpuProfile) getprofile() []byte {
if p == nil {
return nil
}
if p.wholding {
// Release previous log to signal handling side.
// Loop because we are racing against SetCPUProfileRate(0).
for {
n := p.handoff
if n == 0 {
print("runtime: phase error during cpu profile handoff\n")
return nil
}
if n&0x80000000 != 0 {
p.wtoggle = 1 - p.wtoggle
p.wholding = false
p.flushing = true
goto Flush
}
if cas(&p.handoff, n, 0) {
break
}
}
p.wtoggle = 1 - p.wtoggle
p.wholding = false
}
if p.flushing {
goto Flush
}
if !p.on && p.handoff == 0 {
return nil
}
// Wait for new log.
notetsleepg(&p.wait, -1)
noteclear(&p.wait)
switch n := p.handoff; {
case n == 0:
print("runtime: phase error during cpu profile wait\n")
return nil
case n == 0x80000000:
p.flushing = true
goto Flush
default:
n &^= 0x80000000
// Return new log to caller.
p.wholding = true
return uintptrBytes(p.log[p.wtoggle][:n])
}
// In flush mode.
// Add is no longer being called. We own the log.
// Also, p->handoff is non-zero, so flushlog will return false.
// Evict the hash table into the log and return it.
Flush:
for i := range p.hash {
b := &p.hash[i]
for j := range b.entry {
e := &b.entry[j]
if e.count > 0 && !p.evict(e) {
// Filled the log. Stop the loop and return what we've got.
break Flush
}
}
}
// Return pending log data.
if p.nlog > 0 {
// Note that we're using toggle now, not wtoggle,
// because we're working on the log directly.
n := p.nlog
p.nlog = 0
return uintptrBytes(p.log[p.toggle][:n])
}
// Made it through the table without finding anything to log.
if !p.eodSent {
// We may not have space to append this to the partial log buf,
// so we always return a new slice for the end-of-data marker.
p.eodSent = true
return uintptrBytes(eod[:])
}
// Finally done. Clean up and return nil.
p.flushing = false
if !cas(&p.handoff, p.handoff, 0) {
print("runtime: profile flush racing with something\n")
}
return nil
}
func uintptrBytes(p []uintptr) (ret []byte) {
pp := (*sliceStruct)(unsafe.Pointer(&p))
rp := (*sliceStruct)(unsafe.Pointer(&ret))
rp.array = pp.array
rp.len = pp.len * int(unsafe.Sizeof(p[0]))
rp.cap = rp.len
return
}
// CPUProfile 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, CPUProfile returns nil.
// The caller must save the returned data before calling CPUProfile again.
//
// Most clients should use the runtime/pprof package or
// the testing package's -test.cpuprofile flag instead of calling
// CPUProfile directly.
func CPUProfile() []byte {
return cpuprof.getprofile()
}

433
src/pkg/runtime/cpuprof.goc
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@ -1,433 +0,0 @@
// 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.
// Based on algorithms and data structures used in
// http://code.google.com/p/google-perftools/.
//
// The main difference between this code and the google-perftools
// code is that this code is written to allow copying the profile data
// to an arbitrary io.Writer, while the google-perftools code always
// writes to an operating system file.
//
// The signal handler for the profiling clock tick adds a new stack trace
// to a hash table tracking counts for recent traces. Most clock ticks
// hit in the cache. In the event of a cache miss, an entry must be
// evicted from the hash table, copied to a log that will eventually be
// written as profile data. The google-perftools code flushed the
// log itself during the signal handler. This code cannot do that, because
// the io.Writer might block or need system calls or locks that are not
// safe to use from within the signal handler. Instead, we split the log
// into two halves and let the signal handler fill one half while a goroutine
// is writing out the other half. When the signal handler fills its half, it
// offers to swap with the goroutine. If the writer is not done with its half,
// we lose the stack trace for this clock tick (and record that loss).
// The goroutine interacts with the signal handler by calling getprofile() to
// get the next log piece to write, implicitly handing back the last log
// piece it obtained.
//
// The state of this dance between the signal handler and the goroutine
// is encoded in the Profile.handoff field. If handoff == 0, then the goroutine
// is not using either log half and is waiting (or will soon be waiting) for
// a new piece by calling notesleep(&p->wait). If the signal handler
// changes handoff from 0 to non-zero, it must call notewakeup(&p->wait)
// to wake the goroutine. The value indicates the number of entries in the
// log half being handed off. The goroutine leaves the non-zero value in
// place until it has finished processing the log half and then flips the number
// back to zero. Setting the high bit in handoff means that the profiling is over,
// and the goroutine is now in charge of flushing the data left in the hash table
// to the log and returning that data.
//
// The handoff field is manipulated using atomic operations.
// For the most part, the manipulation of handoff is orderly: if handoff == 0
// then the signal handler owns it and can change it to non-zero.
// If handoff != 0 then the goroutine owns it and can change it to zero.
// If that were the end of the story then we would not need to manipulate
// handoff using atomic operations. The operations are needed, however,
// in order to let the log closer set the high bit to indicate "EOF" safely
// in the situation when normally the goroutine "owns" handoff.
package runtime
#include "runtime.h"
#include "arch_GOARCH.h"
#include "malloc.h"
enum
{
HashSize = 1<<10,
LogSize = 1<<17,
Assoc = 4,
MaxStack = 64,
};
typedef struct Profile Profile;
typedef struct Bucket Bucket;
typedef struct Entry Entry;
struct Entry {
uintptr count;
uintptr depth;
uintptr stack[MaxStack];
};
struct Bucket {
Entry entry[Assoc];
};
struct Profile {
bool on; // profiling is on
Note wait; // goroutine waits here
uintptr count; // tick count
uintptr evicts; // eviction count
uintptr lost; // lost ticks that need to be logged
// Active recent stack traces.
Bucket hash[HashSize];
// Log of traces evicted from hash.
// Signal handler has filled log[toggle][:nlog].
// Goroutine is writing log[1-toggle][:handoff].
uintptr log[2][LogSize/2];
uintptr nlog;
int32 toggle;
uint32 handoff;
// Writer state.
// Writer maintains its own toggle to avoid races
// looking at signal handler's toggle.
uint32 wtoggle;
bool wholding; // holding & need to release a log half
bool flushing; // flushing hash table - profile is over
bool eod_sent; // special end-of-data record sent; => flushing
};
static Mutex lk;
static Profile *prof;
static void tick(uintptr*, int32);
static void add(Profile*, uintptr*, int32);
static bool evict(Profile*, Entry*);
static bool flushlog(Profile*);
static uintptr eod[3] = {0, 1, 0};
// LostProfileData is a no-op function used in profiles
// to mark the number of profiling stack traces that were
// discarded due to slow data writers.
static void
LostProfileData(void)
{
}
// SetCPUProfileRate sets the CPU profiling rate.
// The user documentation is in debug.go.
void
runtime·SetCPUProfileRate(intgo hz)
{
uintptr *p;
uintptr n;
// Clamp hz to something reasonable.
if(hz < 0)
hz = 0;
if(hz > 1000000)
hz = 1000000;
runtime·lock(&lk);
if(hz > 0) {
if(prof == nil) {
prof = runtime·sysAlloc(sizeof *prof, &mstats.other_sys);
if(prof == nil) {
runtime·printf("runtime: cpu profiling cannot allocate memory\n");
runtime·unlock(&lk);
return;
}
}
if(prof->on || prof->handoff != 0) {
runtime·printf("runtime: cannot set cpu profile rate until previous profile has finished.\n");
runtime·unlock(&lk);
return;
}
prof->on = true;
p = prof->log[0];
// pprof binary header format.
// http://code.google.com/p/google-perftools/source/browse/trunk/src/profiledata.cc#117
*p++ = 0; // count for header
*p++ = 3; // depth for header
*p++ = 0; // version number
*p++ = 1000000 / hz; // period (microseconds)
*p++ = 0;
prof->nlog = p - prof->log[0];
prof->toggle = 0;
prof->wholding = false;
prof->wtoggle = 0;
prof->flushing = false;
prof->eod_sent = false;
runtime·noteclear(&prof->wait);
runtime·setcpuprofilerate(tick, hz);
} else if(prof != nil && prof->on) {
runtime·setcpuprofilerate(nil, 0);
prof->on = false;
// Now add is not running anymore, and getprofile owns the entire log.
// Set the high bit in prof->handoff to tell getprofile.
for(;;) {
n = prof->handoff;
if(n&0x80000000)
runtime·printf("runtime: setcpuprofile(off) twice");
if(runtime·cas(&prof->handoff, n, n|0x80000000))
break;
}
if(n == 0) {
// we did the transition from 0 -> nonzero so we wake getprofile
runtime·notewakeup(&prof->wait);
}
}
runtime·unlock(&lk);
}
static void
tick(uintptr *pc, int32 n)
{
add(prof, pc, n);
}
// 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. It is allowed to call evict.
static void
add(Profile *p, uintptr *pc, int32 n)
{
int32 i, j;
uintptr h, x;
Bucket *b;
Entry *e;
if(n > MaxStack)
n = MaxStack;
// Compute hash.
h = 0;
for(i=0; i<n; i++) {
h = h<<8 | (h>>(8*(sizeof(h)-1)));
x = pc[i];
h += x*31 + x*7 + x*3;
}
p->count++;
// Add to entry count if already present in table.
b = &p->hash[h%HashSize];
for(i=0; i<Assoc; i++) {
e = &b->entry[i];
if(e->depth != n)
continue;
for(j=0; j<n; j++)
if(e->stack[j] != pc[j])
goto ContinueAssoc;
e->count++;
return;
ContinueAssoc:;
}
// Evict entry with smallest count.
e = &b->entry[0];
for(i=1; i<Assoc; i++)
if(b->entry[i].count < e->count)
e = &b->entry[i];
if(e->count > 0) {
if(!evict(p, e)) {
// Could not evict entry. Record lost stack.
p->lost++;
return;
}
p->evicts++;
}
// Reuse the newly evicted entry.
e->depth = n;
e->count = 1;
for(i=0; i<n; i++)
e->stack[i] = pc[i];
}
// evict copies the given entry's data into the log, so that
// the entry can be reused. evict is called from add, which
// is called from the profiling signal handler, so it must not
// allocate memory or block. It is safe to call flushLog.
// evict returns true if the entry was copied to the log,
// false if there was no room available.
static bool
evict(Profile *p, Entry *e)
{
int32 i, d, nslot;
uintptr *log, *q;
d = e->depth;
nslot = d+2;
log = p->log[p->toggle];
if(p->nlog+nslot > nelem(p->log[0])) {
if(!flushlog(p))
return false;
log = p->log[p->toggle];
}
q = log+p->nlog;
*q++ = e->count;
*q++ = d;
for(i=0; i<d; i++)
*q++ = e->stack[i];
p->nlog = q - log;
e->count = 0;
return true;
}
// flushlog tries to flush the current log and switch to the other one.
// flushlog is called from evict, called from add, called from the signal handler,
// so it cannot allocate memory or block. It can try to swap logs with
// the writing goroutine, as explained in the comment at the top of this file.
static bool
flushlog(Profile *p)
{
uintptr *log, *q;
if(!runtime·cas(&p->handoff, 0, p->nlog))
return false;
runtime·notewakeup(&p->wait);
p->toggle = 1 - p->toggle;
log = p->log[p->toggle];
q = log;
if(p->lost > 0) {
*q++ = p->lost;
*q++ = 1;
*q++ = (uintptr)LostProfileData;
p->lost = 0;
}
p->nlog = q - log;
return true;
}
// getprofile blocks until the next block of profiling data is available
// and returns it as a []byte. It is called from the writing goroutine.
static Slice
getprofile(Profile *p)
{
uint32 i, j, n;
Slice ret;
Bucket *b;
Entry *e;
ret.array = nil;
ret.len = 0;
ret.cap = 0;
if(p == nil)
return ret;
if(p->wholding) {
// Release previous log to signal handling side.
// Loop because we are racing against SetCPUProfileRate(0).
for(;;) {
n = p->handoff;
if(n == 0) {
runtime·printf("runtime: phase error during cpu profile handoff\n");
return ret;
}
if(n & 0x80000000) {
p->wtoggle = 1 - p->wtoggle;
p->wholding = false;
p->flushing = true;
goto flush;
}
if(runtime·cas(&p->handoff, n, 0))
break;
}
p->wtoggle = 1 - p->wtoggle;
p->wholding = false;
}
if(p->flushing)
goto flush;
if(!p->on && p->handoff == 0)
return ret;
// Wait for new log.
runtime·notetsleepg(&p->wait, -1);
runtime·noteclear(&p->wait);
n = p->handoff;
if(n == 0) {
runtime·printf("runtime: phase error during cpu profile wait\n");
return ret;
}
if(n == 0x80000000) {
p->flushing = true;
goto flush;
}
n &= ~0x80000000;
// Return new log to caller.
p->wholding = true;
ret.array = (byte*)p->log[p->wtoggle];
ret.len = n*sizeof(uintptr);
ret.cap = ret.len;
return ret;
flush:
// In flush mode.
// Add is no longer being called. We own the log.
// Also, p->handoff is non-zero, so flushlog will return false.
// Evict the hash table into the log and return it.
for(i=0; i<HashSize; i++) {
b = &p->hash[i];
for(j=0; j<Assoc; j++) {
e = &b->entry[j];
if(e->count > 0 && !evict(p, e)) {
// Filled the log. Stop the loop and return what we've got.
goto breakflush;
}
}
}
breakflush:
// Return pending log data.
if(p->nlog > 0) {
// Note that we're using toggle now, not wtoggle,
// because we're working on the log directly.
ret.array = (byte*)p->log[p->toggle];
ret.len = p->nlog*sizeof(uintptr);
ret.cap = ret.len;
p->nlog = 0;
return ret;
}
// Made it through the table without finding anything to log.
if(!p->eod_sent) {
// We may not have space to append this to the partial log buf,
// so we always return a new slice for the end-of-data marker.
p->eod_sent = true;
ret.array = (byte*)eod;
ret.len = sizeof eod;
ret.cap = ret.len;
return ret;
}
// Finally done. Clean up and return nil.
p->flushing = false;
if(!runtime·cas(&p->handoff, p->handoff, 0))
runtime·printf("runtime: profile flush racing with something\n");
return ret; // set to nil at top of function
}
// CPUProfile returns the next cpu profile block as a []byte.
// The user documentation is in debug.go.
func CPUProfile() (ret Slice) {
ret = getprofile(prof);
}

19
src/pkg/runtime/debug.go
View File

@ -49,22 +49,3 @@ func NumGoroutine() int {
}
func gcount() int32
// CPUProfile 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, CPUProfile returns nil.
// The caller must save the returned data before calling CPUProfile again.
//
// Most clients should use the runtime/pprof package or
// the testing package's -test.cpuprofile flag instead of calling
// CPUProfile directly.
func CPUProfile() []byte
// 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)

17
src/pkg/runtime/proc.c
View File

@ -2395,13 +2395,13 @@ runtime·badreflectcall(void) // called from assembly
static struct {
Mutex lock;
void (*fn)(uintptr*, int32);
int32 hz;
} prof;
static void System(void) {}
static void ExternalCode(void) {}
static void GC(void) {}
extern void runtime·cpuproftick(uintptr*, int32);
extern byte runtime·etext[];
// Called if we receive a SIGPROF signal.
@ -2418,7 +2418,7 @@ runtime·sigprof(uint8 *pc, uint8 *sp, uint8 *lr, G *gp, M *mp)
m = 0;
USED(m);
if(prof.fn == nil || prof.hz == 0)
if(prof.hz == 0)
return;
// Profiling runs concurrently with GC, so it must not allocate.
@ -2537,10 +2537,10 @@ runtime·sigprof(uint8 *pc, uint8 *sp, uint8 *lr, G *gp, M *mp)
}
}
if(prof.fn != nil) {
if(prof.hz != 0) {
runtime·lock(&prof.lock);
if(prof.fn != nil)
prof.fn(stk, n);
if(prof.hz != 0)
runtime·cpuproftick(stk, n);
runtime·unlock(&prof.lock);
}
mp->mallocing--;
@ -2548,15 +2548,11 @@ runtime·sigprof(uint8 *pc, uint8 *sp, uint8 *lr, G *gp, M *mp)
// Arrange to call fn with a traceback hz times a second.
void
runtime·setcpuprofilerate(void (*fn)(uintptr*, int32), int32 hz)
runtime·setcpuprofilerate(int32 hz)
{
// Force sane arguments.
if(hz < 0)
hz = 0;
if(hz == 0)
fn = nil;
if(fn == nil)
hz = 0;
// Disable preemption, otherwise we can be rescheduled to another thread
// that has profiling enabled.
@ -2568,7 +2564,6 @@ runtime·setcpuprofilerate(void (*fn)(uintptr*, int32), int32 hz)
runtime·resetcpuprofiler(0);
runtime·lock(&prof.lock);
prof.fn = fn;
prof.hz = hz;
runtime·unlock(&prof.lock);
runtime·lock(&runtime·sched.lock);

2
src/pkg/runtime/runtime.h
View File

@ -864,7 +864,7 @@ void runtime·freezetheworld(void);
void runtime·unwindstack(G*, byte*);
void runtime·sigprof(uint8 *pc, uint8 *sp, uint8 *lr, G *gp, M *mp);
void runtime·resetcpuprofiler(int32);
void runtime·setcpuprofilerate(void(*)(uintptr*, int32), int32);
void runtime·setcpuprofilerate(int32);
void runtime·usleep(uint32);
int64 runtime·cputicks(void);
int64 runtime·tickspersecond(void);