// 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 (
"unsafe"
)
// NOTE(rsc): Everything here could use cas if contention became an issue.
var proflock 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
// size of bucket hash table
buckHashSize = 179999
// max depth of stack to record in bucket
maxStack = 32
)
type bucketType int
// A bucket holds per-call-stack profiling information.
// The representation is a bit sleazy, inherited from C.
// This struct defines the bucket header. It is followed in
// memory by the stack words and then the actual record
// data, either a memRecord or a blockRecord.
//
// Per-call-stack profiling information.
// Lookup by hashing call stack into a linked-list hash table.
type bucket struct {
next *bucket
allnext *bucket
typ bucketType // memBucket or blockBucket
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.
//
// Mallocs are accounted in recent stats.
// Explicit frees are accounted in recent stats.
// GC frees are accounted in prev stats.
// After GC prev stats are added to final stats and
// recent stats are moved into prev stats.
allocs uintptr
frees uintptr
alloc_bytes uintptr
free_bytes uintptr
// changes between next-to-last GC and last GC
prev_allocs uintptr
prev_frees uintptr
prev_alloc_bytes uintptr
prev_free_bytes uintptr
// changes since last GC
recent_allocs uintptr
recent_frees uintptr
recent_alloc_bytes uintptr
recent_free_bytes uintptr
}
// A blockRecord is the bucket data for a bucket of type blockProfile,
// part of the blocking profile.
type blockRecord struct {
count int64
cycles int64
}
var (
mbuckets *bucket // memory profile buckets
bbuckets *bucket // blocking profile buckets
buckhash *[179999]*bucket
bucketmem uintptr
)
// 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:
size += unsafe.Sizeof(blockRecord{})
}
b := (*bucket)(persistentalloc(size, 0, &memstats.buckhash_sys))
bucketmem += size
b.typ = typ
b.nstk = uintptr(nstk)
return b
}
// stk returns the slice in b holding the stack.
func (b *bucket) stk() []uintptr {
stk := (*[maxStack]uintptr)(add(unsafe.Pointer(b), unsafe.Sizeof(*b)))
return stk[:b.nstk:b.nstk]
}
// mp returns the memRecord associated with the memProfile bucket b.
func (b *bucket) mp() *memRecord {
if b.typ != memProfile {
throw("bad use of bucket.mp")
}
data := add(unsafe.Pointer(b), unsafe.Sizeof(*b)+b.nstk*unsafe.Sizeof(uintptr(0)))
return (*memRecord)(data)
}
// bp returns the blockRecord associated with the blockProfile bucket b.
func (b *bucket) bp() *blockRecord {
if b.typ != blockProfile {
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 {
if buckhash == nil {
buckhash = (*[buckHashSize]*bucket)(sysAlloc(unsafe.Sizeof(*buckhash), &memstats.buckhash_sys))
if buckhash == nil {
throw("runtime: cannot allocate memory")
}
}
// 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)
for b := buckhash[i]; 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
}
// Create new bucket.
b := newBucket(typ, len(stk))
copy(b.stk(), stk)
b.hash = h
b.size = size
b.next = buckhash[i]
buckhash[i] = b
if typ == memProfile {
b.allnext = mbuckets
mbuckets = b
} else {
b.allnext = bbuckets
bbuckets = b
}
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
}
func mprof_GC() {
for b := mbuckets; b != nil; b = b.allnext {
mp := b.mp()
mp.allocs += mp.prev_allocs
mp.frees += mp.prev_frees
mp.alloc_bytes += mp.prev_alloc_bytes
mp.free_bytes += mp.prev_free_bytes
mp.prev_allocs = mp.recent_allocs
mp.prev_frees = mp.recent_frees
mp.prev_alloc_bytes = mp.recent_alloc_bytes
mp.prev_free_bytes = mp.recent_free_bytes
mp.recent_allocs = 0
mp.recent_frees = 0
mp.recent_alloc_bytes = 0
mp.recent_free_bytes = 0
}
}
// Record that a gc just happened: all the 'recent' statistics are now real.
func mProf_GC() {
lock(&proflock)
mprof_GC()
unlock(&proflock)
}
// Called by malloc to record a profiled block.
func mProf_Malloc(p unsafe.Pointer, size uintptr) {
var stk [maxStack]uintptr
nstk := callers(4, stk[:])
lock(&proflock)
b := stkbucket(memProfile, size, stk[:nstk], true)
mp := b.mp()
mp.recent_allocs++
mp.recent_alloc_bytes += size
unlock(&proflock)
// Setprofilebucket locks a bunch of other mutexes, so we call it outside of proflock.
// This reduces potential contention and chances of deadlocks.
// Since the object must be alive during 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, freed bool) {
lock(&proflock)
mp := b.mp()
if freed {
mp.recent_frees++
mp.recent_free_bytes += size
} else {
mp.prev_frees++
mp.prev_free_bytes += size
}
unlock(&proflock)
}
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
}
}
atomicstore64(&blockprofilerate, uint64(r))
}
func blockevent(cycles int64, skip int) {
if cycles <= 0 {
cycles = 1
}
rate := int64(atomicload64(&blockprofilerate))
if rate <= 0 || (rate > cycles && int64(fastrand1())%rate > cycles) {
return
}
gp := getg()
var nstk int
var stk [maxStack]uintptr
if gp.m.curg == nil || gp.m.curg == gp {
nstk = callers(skip, stk[:])
} else {
nstk = gcallers(gp.m.curg, skip, stk[:])
}
lock(&proflock)
b := stkbucket(blockProfile, 0, stk[:nstk], true)
b.bp().count++
b.bp().cycles += cycles
unlock(&proflock)
}
// 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
// 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 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.
//
// 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) {
lock(&proflock)
clear := true
for b := mbuckets; b != nil; b = b.allnext {
mp := b.mp()
if inuseZero || mp.alloc_bytes != mp.free_bytes {
n++
}
if mp.allocs != 0 || mp.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 stats as if a GC just happened, and recount buckets.
mprof_GC()
mprof_GC()
n = 0
for b := mbuckets; b != nil; b = b.allnext {
mp := b.mp()
if inuseZero || mp.alloc_bytes != mp.free_bytes {
n++
}
}
}
if n <= len(p) {
ok = true
idx := 0
for b := mbuckets; b != nil; b = b.allnext {
mp := b.mp()
if inuseZero || mp.alloc_bytes != mp.free_bytes {
record(&p[idx], b)
idx++
}
}
}
unlock(&proflock)
return
}
// Write b's data to r.
func record(r *MemProfileRecord, b *bucket) {
mp := b.mp()
r.AllocBytes = int64(mp.alloc_bytes)
r.FreeBytes = int64(mp.free_bytes)
r.AllocObjects = int64(mp.allocs)
r.FreeObjects = int64(mp.frees)
copy(r.Stack0[:], b.stk())
for i := int(b.nstk); i < len(r.Stack0); i++ {
r.Stack0[i] = 0
}
}
func iterate_memprof(fn func(*bucket, uintptr, *uintptr, uintptr, uintptr, uintptr)) {
lock(&proflock)
for b := mbuckets; b != nil; b = b.allnext {
mp := b.mp()
fn(b, uintptr(b.nstk), &b.stk()[0], b.size, mp.allocs, mp.frees)
}
unlock(&proflock)
}
// BlockProfileRecord describes blocking events originated
// at a particular call sequence (stack trace).
type BlockProfileRecord struct {
Count int64
Cycles int64
StackRecord
}
// BlockProfile returns n, the number of records in the current blocking profile.
// If len(p) >= n, BlockProfile copies the profile into p and returns n, true.
// If len(p) < n, BlockProfile does not change p and returns n, false.
//
// Most clients should use the runtime/pprof package or
// the testing package's -test.blockprofile flag instead
// of calling BlockProfile directly.
func BlockProfile(p []BlockProfileRecord) (n int, ok bool) {
lock(&proflock)
for b := bbuckets; b != nil; b = b.allnext {
n++
}
if n <= len(p) {
ok = true
for b := bbuckets; b != nil; b = b.allnext {
bp := b.bp()
r := &p[0]
r.Count = int64(bp.count)
r.Cycles = int64(bp.cycles)
i := copy(r.Stack0[:], b.stk())
for ; i < len(r.Stack0); i++ {
r.Stack0[i] = 0
}
p = p[1:]
}
}
unlock(&proflock)
return
}
// ThreadCreateProfile returns n, the number of records in the thread creation profile.
// If len(p) >= n, ThreadCreateProfile copies the profile into p and returns n, true.
// If len(p) < n, ThreadCreateProfile does not change p and returns n, false.
//
// Most clients should use the runtime/pprof package instead
// of calling ThreadCreateProfile directly.
func ThreadCreateProfile(p []StackRecord) (n int, ok bool) {
first := (*m)(atomicloadp(unsafe.Pointer(&allm)))
for mp := first; mp != nil; mp = mp.alllink {
n++
}
if n <= len(p) {
ok = true
i := 0
for mp := first; mp != nil; mp = mp.alllink {
for s := range mp.createstack {
p[i].Stack0[s] = uintptr(mp.createstack[s])
}
i++
}
}
return
}
// 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) {
n = NumGoroutine()
if n <= len(p) {
gp := getg()
stopTheWorld("profile")
n = NumGoroutine()
if n <= len(p) {
ok = true
r := p
sp := getcallersp(unsafe.Pointer(&p))
pc := getcallerpc(unsafe.Pointer(&p))
systemstack(func() {
saveg(pc, sp, gp, &r[0])
})
r = r[1:]
for _, gp1 := range allgs {
if gp1 == gp || readgstatus(gp1) == _Gdead {
continue
}
saveg(^uintptr(0), ^uintptr(0), gp1, &r[0])
r = r[1:]
}
}
startTheWorld()
}
return n, ok
}
func saveg(pc, sp uintptr, gp *g, r *StackRecord) {
n := gentraceback(pc, sp, 0, gp, 0, &r.Stack0[0], len(r.Stack0), nil, nil, 0)
if n < len(r.Stack0) {
r.Stack0[n] = 0
}
}
// Stack formats a stack trace of the calling goroutine into buf
// and returns the number of bytes written to buf.
// If all is true, Stack formats stack traces of all other goroutines
// into buf after the trace for the current goroutine.
func Stack(buf []byte, all bool) int {
if all {
stopTheWorld("stack trace")
}
n := 0
if len(buf) > 0 {
gp := getg()
sp := getcallersp(unsafe.Pointer(&buf))
pc := getcallerpc(unsafe.Pointer(&buf))
systemstack(func() {
g0 := getg()
g0.writebuf = buf[0:0:len(buf)]
goroutineheader(gp)
traceback(pc, sp, 0, gp)
if all {
tracebackothers(gp)
}
n = len(g0.writebuf)
g0.writebuf = nil
})
}
if all {
startTheWorld()
}
return n
}
// Tracing of alloc/free/gc.
var tracelock mutex
func tracealloc(p unsafe.Pointer, size uintptr, typ *_type) {
lock(&tracelock)
gp := getg()
gp.m.traceback = 2
if typ == nil {
print("tracealloc(", p, ", ", hex(size), ")\n")
} else {
print("tracealloc(", p, ", ", hex(size), ", ", *typ._string, ")\n")
}
if gp.m.curg == nil || gp == gp.m.curg {
goroutineheader(gp)
pc := getcallerpc(unsafe.Pointer(&p))
sp := getcallersp(unsafe.Pointer(&p))
systemstack(func() {
traceback(pc, sp, 0, gp)
})
} else {
goroutineheader(gp.m.curg)
traceback(^uintptr(0), ^uintptr(0), 0, gp.m.curg)
}
print("\n")
gp.m.traceback = 0
unlock(&tracelock)
}
func tracefree(p unsafe.Pointer, size uintptr) {
lock(&tracelock)
gp := getg()
gp.m.traceback = 2
print("tracefree(", p, ", ", hex(size), ")\n")
goroutineheader(gp)
pc := getcallerpc(unsafe.Pointer(&p))
sp := getcallersp(unsafe.Pointer(&p))
systemstack(func() {
traceback(pc, sp, 0, gp)
})
print("\n")
gp.m.traceback = 0
unlock(&tracelock)
}
func tracegc() {
lock(&tracelock)
gp := getg()
gp.m.traceback = 2
print("tracegc()\n")
// running on m->g0 stack; show all non-g0 goroutines
tracebackothers(gp)
print("end tracegc\n")
print("\n")
gp.m.traceback = 0
unlock(&tracelock)
}