1 // Copyright 2009 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
6 // Patterned after tcmalloc's algorithms; shorter code.
11 "runtime/internal/atomic"
15 // NOTE(rsc): Everything here could use cas if contention became an issue.
18 // All memory allocations are local and do not escape outside of the profiler.
19 // The profiler is forbidden from referring to garbage-collected memory.
23 memProfile bucketType = 1 + iota
27 // size of bucket hash table
30 // max depth of stack to record in bucket
36 // A bucket holds per-call-stack profiling information.
37 // The representation is a bit sleazy, inherited from C.
38 // This struct defines the bucket header. It is followed in
39 // memory by the stack words and then the actual record
40 // data, either a memRecord or a blockRecord.
42 // Per-call-stack profiling information.
43 // Lookup by hashing call stack into a linked-list hash table.
51 typ bucketType // memBucket or blockBucket (includes mutexProfile)
57 // A memRecord is the bucket data for a bucket of type memProfile,
58 // part of the memory profile.
59 type memRecord struct {
60 // The following complex 3-stage scheme of stats accumulation
61 // is required to obtain a consistent picture of mallocs and frees
62 // for some point in time.
63 // The problem is that mallocs come in real time, while frees
64 // come only after a GC during concurrent sweeping. So if we would
65 // naively count them, we would get a skew toward mallocs.
67 // Hence, we delay information to get consistent snapshots as
68 // of mark termination. Allocations count toward the next mark
69 // termination's snapshot, while sweep frees count toward the
70 // previous mark termination's snapshot:
74 // .·˙ | .·˙ | .·˙ | .·˙ |
75 // .·˙ | .·˙ | .·˙ | .·˙ |
76 // .·˙ |.·˙ |.·˙ |.·˙ |
86 // Since we can't publish a consistent snapshot until all of
87 // the sweep frees are accounted for, we wait until the next
88 // mark termination ("MT" above) to publish the previous mark
89 // termination's snapshot ("P" above). To do this, allocation
90 // and free events are accounted to *future* heap profile
91 // cycles ("C+n" above) and we only publish a cycle once all
92 // of the events from that cycle must be done. Specifically:
94 // Mallocs are accounted to cycle C+2.
95 // Explicit frees are accounted to cycle C+2.
96 // GC frees (done during sweeping) are accounted to cycle C+1.
98 // After mark termination, we increment the global heap
99 // profile cycle counter and accumulate the stats from cycle C
100 // into the active profile.
102 // active is the currently published profile. A profiling
103 // cycle can be accumulated into active once its complete.
104 active memRecordCycle
106 // future records the profile events we're counting for cycles
107 // that have not yet been published. This is ring buffer
108 // indexed by the global heap profile cycle C and stores
109 // cycles C, C+1, and C+2. Unlike active, these counts are
110 // only for a single cycle; they are not cumulative across
113 // We store cycle C here because there's a window between when
114 // C becomes the active cycle and when we've flushed it to
116 future [3]memRecordCycle
120 type memRecordCycle struct {
121 allocs, frees uintptr
122 alloc_bytes, free_bytes uintptr
125 // add accumulates b into a. It does not zero b.
126 func (a *memRecordCycle) add(b *memRecordCycle) {
129 a.alloc_bytes += b.alloc_bytes
130 a.free_bytes += b.free_bytes
133 // A blockRecord is the bucket data for a bucket of type blockProfile,
134 // which is used in blocking and mutex profiles.
135 type blockRecord struct {
141 mbuckets *bucket // memory profile buckets
142 bbuckets *bucket // blocking profile buckets
143 xbuckets *bucket // mutex profile buckets
144 buckhash *[179999]*bucket
148 // All fields in mProf are protected by proflock.
150 // cycle is the global heap profile cycle. This wraps
151 // at mProfCycleWrap.
153 // flushed indicates that future[cycle] in all buckets
154 // has been flushed to the active profile.
159 const mProfCycleWrap = uint32(len(memRecord{}.future)) * (2 << 24)
161 // newBucket allocates a bucket with the given type and number of stack entries.
162 func newBucket(typ bucketType, nstk int) *bucket {
163 size := unsafe.Sizeof(bucket{}) + uintptr(nstk)*unsafe.Sizeof(uintptr(0))
166 throw("invalid profile bucket type")
168 size += unsafe.Sizeof(memRecord{})
169 case blockProfile, mutexProfile:
170 size += unsafe.Sizeof(blockRecord{})
173 b := (*bucket)(persistentalloc(size, 0, &memstats.buckhash_sys))
176 b.nstk = uintptr(nstk)
180 // stk returns the slice in b holding the stack.
181 func (b *bucket) stk() []uintptr {
182 stk := (*[maxStack]uintptr)(add(unsafe.Pointer(b), unsafe.Sizeof(*b)))
183 return stk[:b.nstk:b.nstk]
186 // mp returns the memRecord associated with the memProfile bucket b.
187 func (b *bucket) mp() *memRecord {
188 if b.typ != memProfile {
189 throw("bad use of bucket.mp")
191 data := add(unsafe.Pointer(b), unsafe.Sizeof(*b)+b.nstk*unsafe.Sizeof(uintptr(0)))
192 return (*memRecord)(data)
195 // bp returns the blockRecord associated with the blockProfile bucket b.
196 func (b *bucket) bp() *blockRecord {
197 if b.typ != blockProfile && b.typ != mutexProfile {
198 throw("bad use of bucket.bp")
200 data := add(unsafe.Pointer(b), unsafe.Sizeof(*b)+b.nstk*unsafe.Sizeof(uintptr(0)))
201 return (*blockRecord)(data)
204 // Return the bucket for stk[0:nstk], allocating new bucket if needed.
205 func stkbucket(typ bucketType, size uintptr, stk []uintptr, alloc bool) *bucket {
207 buckhash = (*[buckHashSize]*bucket)(sysAlloc(unsafe.Sizeof(*buckhash), &memstats.buckhash_sys))
209 throw("runtime: cannot allocate memory")
215 for _, pc := range stk {
228 i := int(h % buckHashSize)
229 for b := buckhash[i]; b != nil; b = b.next {
230 if b.typ == typ && b.hash == h && b.size == size && eqslice(b.stk(), stk) {
239 // Create new bucket.
240 b := newBucket(typ, len(stk))
246 if typ == memProfile {
249 } else if typ == mutexProfile {
259 func eqslice(x, y []uintptr) bool {
260 if len(x) != len(y) {
263 for i, xi := range x {
271 // mProf_NextCycle publishes the next heap profile cycle and creates a
272 // fresh heap profile cycle. This operation is fast and can be done
273 // during STW. The caller must call mProf_Flush before calling
274 // mProf_NextCycle again.
276 // This is called by mark termination during STW so allocations and
277 // frees after the world is started again count towards a new heap
279 func mProf_NextCycle() {
281 // We explicitly wrap mProf.cycle rather than depending on
282 // uint wraparound because the memRecord.future ring does not
283 // itself wrap at a power of two.
284 mProf.cycle = (mProf.cycle + 1) % mProfCycleWrap
285 mProf.flushed = false
289 // mProf_Flush flushes the events from the current heap profiling
290 // cycle into the active profile. After this it is safe to start a new
291 // heap profiling cycle with mProf_NextCycle.
293 // This is called by GC after mark termination starts the world. In
294 // contrast with mProf_NextCycle, this is somewhat expensive, but safe
295 // to do concurrently.
305 func mProf_FlushLocked() {
307 for b := mbuckets; b != nil; b = b.allnext {
310 // Flush cycle C into the published profile and clear
312 mpc := &mp.future[c%uint32(len(mp.future))]
314 *mpc = memRecordCycle{}
318 // Called by malloc to record a profiled block.
319 func mProf_Malloc(p unsafe.Pointer, size uintptr) {
320 var stk [maxStack]uintptr
321 nstk := callers(4, stk[:])
323 b := stkbucket(memProfile, size, stk[:nstk], true)
326 mpc := &mp.future[(c+2)%uint32(len(mp.future))]
328 mpc.alloc_bytes += size
331 // Setprofilebucket locks a bunch of other mutexes, so we call it outside of proflock.
332 // This reduces potential contention and chances of deadlocks.
333 // Since the object must be alive during call to mProf_Malloc,
334 // it's fine to do this non-atomically.
336 setprofilebucket(p, b)
340 // Called when freeing a profiled block.
341 func mProf_Free(b *bucket, size uintptr) {
345 mpc := &mp.future[(c+1)%uint32(len(mp.future))]
347 mpc.free_bytes += size
351 var blockprofilerate uint64 // in CPU ticks
353 // SetBlockProfileRate controls the fraction of goroutine blocking events
354 // that are reported in the blocking profile. The profiler aims to sample
355 // an average of one blocking event per rate nanoseconds spent blocked.
357 // To include every blocking event in the profile, pass rate = 1.
358 // To turn off profiling entirely, pass rate <= 0.
359 func SetBlockProfileRate(rate int) {
362 r = 0 // disable profiling
363 } else if rate == 1 {
364 r = 1 // profile everything
366 // convert ns to cycles, use float64 to prevent overflow during multiplication
367 r = int64(float64(rate) * float64(tickspersecond()) / (1000 * 1000 * 1000))
373 atomic.Store64(&blockprofilerate, uint64(r))
376 func blockevent(cycles int64, skip int) {
380 if blocksampled(cycles) {
381 saveblockevent(cycles, skip+1, blockProfile)
385 func blocksampled(cycles int64) bool {
386 rate := int64(atomic.Load64(&blockprofilerate))
387 if rate <= 0 || (rate > cycles && int64(fastrand())%rate > cycles) {
393 func saveblockevent(cycles int64, skip int, which bucketType) {
396 var stk [maxStack]uintptr
397 if gp.m.curg == nil || gp.m.curg == gp {
398 nstk = callers(skip, stk[:])
400 nstk = gcallers(gp.m.curg, skip, stk[:])
403 b := stkbucket(which, 0, stk[:nstk], true)
405 b.bp().cycles += cycles
409 var mutexprofilerate uint64 // fraction sampled
411 // SetMutexProfileFraction controls the fraction of mutex contention events
412 // that are reported in the mutex profile. On average 1/rate events are
413 // reported. The previous rate is returned.
415 // To turn off profiling entirely, pass rate 0.
416 // To just read the current rate, pass rate -1.
417 // (For n>1 the details of sampling may change.)
418 func SetMutexProfileFraction(rate int) int {
420 return int(mutexprofilerate)
422 old := mutexprofilerate
423 atomic.Store64(&mutexprofilerate, uint64(rate))
427 //go:linkname mutexevent sync.event
428 func mutexevent(cycles int64, skip int) {
432 rate := int64(atomic.Load64(&mutexprofilerate))
433 // TODO(pjw): measure impact of always calling fastrand vs using something
434 // like malloc.go:nextSample()
435 if rate > 0 && int64(fastrand())%rate == 0 {
436 saveblockevent(cycles, skip+1, mutexProfile)
440 // Go interface to profile data.
442 // A StackRecord describes a single execution stack.
443 type StackRecord struct {
444 Stack0 [32]uintptr // stack trace for this record; ends at first 0 entry
447 // Stack returns the stack trace associated with the record,
448 // a prefix of r.Stack0.
449 func (r *StackRecord) Stack() []uintptr {
450 for i, v := range r.Stack0 {
458 // MemProfileRate controls the fraction of memory allocations
459 // that are recorded and reported in the memory profile.
460 // The profiler aims to sample an average of
461 // one allocation per MemProfileRate bytes allocated.
463 // To include every allocated block in the profile, set MemProfileRate to 1.
464 // To turn off profiling entirely, set MemProfileRate to 0.
466 // The tools that process the memory profiles assume that the
467 // profile rate is constant across the lifetime of the program
468 // and equal to the current value. Programs that change the
469 // memory profiling rate should do so just once, as early as
470 // possible in the execution of the program (for example,
471 // at the beginning of main).
472 var MemProfileRate int = 512 * 1024
474 // A MemProfileRecord describes the live objects allocated
475 // by a particular call sequence (stack trace).
476 type MemProfileRecord struct {
477 AllocBytes, FreeBytes int64 // number of bytes allocated, freed
478 AllocObjects, FreeObjects int64 // number of objects allocated, freed
479 Stack0 [32]uintptr // stack trace for this record; ends at first 0 entry
482 // InUseBytes returns the number of bytes in use (AllocBytes - FreeBytes).
483 func (r *MemProfileRecord) InUseBytes() int64 { return r.AllocBytes - r.FreeBytes }
485 // InUseObjects returns the number of objects in use (AllocObjects - FreeObjects).
486 func (r *MemProfileRecord) InUseObjects() int64 {
487 return r.AllocObjects - r.FreeObjects
490 // Stack returns the stack trace associated with the record,
491 // a prefix of r.Stack0.
492 func (r *MemProfileRecord) Stack() []uintptr {
493 for i, v := range r.Stack0 {
501 // MemProfile returns a profile of memory allocated and freed per allocation
504 // MemProfile returns n, the number of records in the current memory profile.
505 // If len(p) >= n, MemProfile copies the profile into p and returns n, true.
506 // If len(p) < n, MemProfile does not change p and returns n, false.
508 // If inuseZero is true, the profile includes allocation records
509 // where r.AllocBytes > 0 but r.AllocBytes == r.FreeBytes.
510 // These are sites where memory was allocated, but it has all
511 // been released back to the runtime.
513 // The returned profile may be up to two garbage collection cycles old.
514 // This is to avoid skewing the profile toward allocations; because
515 // allocations happen in real time but frees are delayed until the garbage
516 // collector performs sweeping, the profile only accounts for allocations
517 // that have had a chance to be freed by the garbage collector.
519 // Most clients should use the runtime/pprof package or
520 // the testing package's -test.memprofile flag instead
521 // of calling MemProfile directly.
522 func MemProfile(p []MemProfileRecord, inuseZero bool) (n int, ok bool) {
524 // If we're between mProf_NextCycle and mProf_Flush, take care
525 // of flushing to the active profile so we only have to look
526 // at the active profile below.
529 for b := mbuckets; b != nil; b = b.allnext {
531 if inuseZero || mp.active.alloc_bytes != mp.active.free_bytes {
534 if mp.active.allocs != 0 || mp.active.frees != 0 {
539 // Absolutely no data, suggesting that a garbage collection
540 // has not yet happened. In order to allow profiling when
541 // garbage collection is disabled from the beginning of execution,
542 // accumulate all of the cycles, and recount buckets.
544 for b := mbuckets; b != nil; b = b.allnext {
546 for c := range mp.future {
547 mp.active.add(&mp.future[c])
548 mp.future[c] = memRecordCycle{}
550 if inuseZero || mp.active.alloc_bytes != mp.active.free_bytes {
558 for b := mbuckets; b != nil; b = b.allnext {
560 if inuseZero || mp.active.alloc_bytes != mp.active.free_bytes {
570 // Write b's data to r.
571 func record(r *MemProfileRecord, b *bucket) {
573 r.AllocBytes = int64(mp.active.alloc_bytes)
574 r.FreeBytes = int64(mp.active.free_bytes)
575 r.AllocObjects = int64(mp.active.allocs)
576 r.FreeObjects = int64(mp.active.frees)
578 racewriterangepc(unsafe.Pointer(&r.Stack0[0]), unsafe.Sizeof(r.Stack0), getcallerpc(unsafe.Pointer(&r)), funcPC(MemProfile))
581 msanwrite(unsafe.Pointer(&r.Stack0[0]), unsafe.Sizeof(r.Stack0))
583 copy(r.Stack0[:], b.stk())
584 for i := int(b.nstk); i < len(r.Stack0); i++ {
589 func iterate_memprof(fn func(*bucket, uintptr, *uintptr, uintptr, uintptr, uintptr)) {
591 for b := mbuckets; b != nil; b = b.allnext {
593 fn(b, b.nstk, &b.stk()[0], b.size, mp.active.allocs, mp.active.frees)
598 // BlockProfileRecord describes blocking events originated
599 // at a particular call sequence (stack trace).
600 type BlockProfileRecord struct {
606 // BlockProfile returns n, the number of records in the current blocking profile.
607 // If len(p) >= n, BlockProfile copies the profile into p and returns n, true.
608 // If len(p) < n, BlockProfile does not change p and returns n, false.
610 // Most clients should use the runtime/pprof package or
611 // the testing package's -test.blockprofile flag instead
612 // of calling BlockProfile directly.
613 func BlockProfile(p []BlockProfileRecord) (n int, ok bool) {
615 for b := bbuckets; b != nil; b = b.allnext {
620 for b := bbuckets; b != nil; b = b.allnext {
626 racewriterangepc(unsafe.Pointer(&r.Stack0[0]), unsafe.Sizeof(r.Stack0), getcallerpc(unsafe.Pointer(&p)), funcPC(BlockProfile))
629 msanwrite(unsafe.Pointer(&r.Stack0[0]), unsafe.Sizeof(r.Stack0))
631 i := copy(r.Stack0[:], b.stk())
632 for ; i < len(r.Stack0); i++ {
642 // MutexProfile returns n, the number of records in the current mutex profile.
643 // If len(p) >= n, MutexProfile copies the profile into p and returns n, true.
644 // Otherwise, MutexProfile does not change p, and returns n, false.
646 // Most clients should use the runtime/pprof package
647 // instead of calling MutexProfile directly.
648 func MutexProfile(p []BlockProfileRecord) (n int, ok bool) {
650 for b := xbuckets; b != nil; b = b.allnext {
655 for b := xbuckets; b != nil; b = b.allnext {
658 r.Count = int64(bp.count)
660 i := copy(r.Stack0[:], b.stk())
661 for ; i < len(r.Stack0); i++ {
671 // ThreadCreateProfile returns n, the number of records in the thread creation profile.
672 // If len(p) >= n, ThreadCreateProfile copies the profile into p and returns n, true.
673 // If len(p) < n, ThreadCreateProfile does not change p and returns n, false.
675 // Most clients should use the runtime/pprof package instead
676 // of calling ThreadCreateProfile directly.
677 func ThreadCreateProfile(p []StackRecord) (n int, ok bool) {
678 first := (*m)(atomic.Loadp(unsafe.Pointer(&allm)))
679 for mp := first; mp != nil; mp = mp.alllink {
685 for mp := first; mp != nil; mp = mp.alllink {
686 p[i].Stack0 = mp.createstack
693 // GoroutineProfile returns n, the number of records in the active goroutine stack profile.
694 // If len(p) >= n, GoroutineProfile copies the profile into p and returns n, true.
695 // If len(p) < n, GoroutineProfile does not change p and returns n, false.
697 // Most clients should use the runtime/pprof package instead
698 // of calling GoroutineProfile directly.
699 func GoroutineProfile(p []StackRecord) (n int, ok bool) {
702 isOK := func(gp1 *g) bool {
703 // Checking isSystemGoroutine here makes GoroutineProfile
704 // consistent with both NumGoroutine and Stack.
705 return gp1 != gp && readgstatus(gp1) != _Gdead && !isSystemGoroutine(gp1)
708 stopTheWorld("profile")
711 for _, gp1 := range allgs {
721 // Save current goroutine.
722 sp := getcallersp(unsafe.Pointer(&p))
723 pc := getcallerpc(unsafe.Pointer(&p))
725 saveg(pc, sp, gp, &r[0])
729 // Save other goroutines.
730 for _, gp1 := range allgs {
733 // Should be impossible, but better to return a
734 // truncated profile than to crash the entire process.
737 saveg(^uintptr(0), ^uintptr(0), gp1, &r[0])
748 func saveg(pc, sp uintptr, gp *g, r *StackRecord) {
749 n := gentraceback(pc, sp, 0, gp, 0, &r.Stack0[0], len(r.Stack0), nil, nil, 0)
750 if n < len(r.Stack0) {
755 // Stack formats a stack trace of the calling goroutine into buf
756 // and returns the number of bytes written to buf.
757 // If all is true, Stack formats stack traces of all other goroutines
758 // into buf after the trace for the current goroutine.
759 func Stack(buf []byte, all bool) int {
761 stopTheWorld("stack trace")
767 sp := getcallersp(unsafe.Pointer(&buf))
768 pc := getcallerpc(unsafe.Pointer(&buf))
771 // Force traceback=1 to override GOTRACEBACK setting,
772 // so that Stack's results are consistent.
773 // GOTRACEBACK is only about crash dumps.
775 g0.writebuf = buf[0:0:len(buf)]
777 traceback(pc, sp, 0, gp)
793 // Tracing of alloc/free/gc.
797 func tracealloc(p unsafe.Pointer, size uintptr, typ *_type) {
802 print("tracealloc(", p, ", ", hex(size), ")\n")
804 print("tracealloc(", p, ", ", hex(size), ", ", typ.string(), ")\n")
806 if gp.m.curg == nil || gp == gp.m.curg {
808 pc := getcallerpc(unsafe.Pointer(&p))
809 sp := getcallersp(unsafe.Pointer(&p))
811 traceback(pc, sp, 0, gp)
814 goroutineheader(gp.m.curg)
815 traceback(^uintptr(0), ^uintptr(0), 0, gp.m.curg)
822 func tracefree(p unsafe.Pointer, size uintptr) {
826 print("tracefree(", p, ", ", hex(size), ")\n")
828 pc := getcallerpc(unsafe.Pointer(&p))
829 sp := getcallersp(unsafe.Pointer(&p))
831 traceback(pc, sp, 0, gp)
843 // running on m->g0 stack; show all non-g0 goroutines
845 print("end tracegc\n")