gcc/libgo/runtime/mprof.goc

// 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
#include "runtime.h"
#include "arch.h"
#include "malloc.h"
#include "defs.h"
#include "go-type.h"
#include "go-string.h"

// NOTE(rsc): Everything here could use cas if contention became an issue.
static Lock proflock;

// All memory allocations are local and do not escape outside of the profiler.
// The profiler is forbidden from referring to garbage-collected memory.

enum { MProf, BProf };  // profile types

// Per-call-stack profiling information.
// Lookup by hashing call stack into a linked-list hash table.
struct Bucket
{
	Bucket	*next;	// next in hash list
	Bucket	*allnext;	// next in list of all mbuckets/bbuckets
	int32	typ;
	// Generally unions can break precise GC,
	// this one is fine because it does not contain pointers.
	union
	{
		struct  // typ == MProf
		{
			// 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.
			uintptr	allocs;
			uintptr	frees;
			uintptr	alloc_bytes;
			uintptr	free_bytes;

			uintptr	prev_allocs;  // since last but one till last gc
			uintptr	prev_frees;
			uintptr	prev_alloc_bytes;
			uintptr	prev_free_bytes;

			uintptr	recent_allocs;  // since last gc till now
			uintptr	recent_frees;
			uintptr	recent_alloc_bytes;
			uintptr	recent_free_bytes;

		};
		struct  // typ == BProf
		{
			int64	count;
			int64	cycles;
		};
	};
	uintptr	hash;	// hash of size + stk
	uintptr	size;
	uintptr	nstk;
	Location stk[1];
};
enum {
	BuckHashSize = 179999,
};
static Bucket **buckhash;
static Bucket *mbuckets;  // memory profile buckets
static Bucket *bbuckets;  // blocking profile buckets
static uintptr bucketmem;

// Return the bucket for stk[0:nstk], allocating new bucket if needed.
static Bucket*
stkbucket(int32 typ, uintptr size, Location *stk, int32 nstk, bool alloc)
{
	int32 i, j;
	uintptr h;
	Bucket *b;

	if(buckhash == nil) {
		buckhash = runtime_SysAlloc(BuckHashSize*sizeof buckhash[0], &mstats.buckhash_sys);
		if(buckhash == nil)
			runtime_throw("runtime: cannot allocate memory");
	}

	// Hash stack.
	h = 0;
	for(i=0; i<nstk; i++) {
		h += stk[i].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 = h%BuckHashSize;
	for(b = buckhash[i]; b; b=b->next) {
		if(b->typ == typ && b->hash == h && b->size == size && b->nstk == (uintptr)nstk) {
			for(j = 0; j < nstk; j++) {
				if(b->stk[j].pc != stk[j].pc ||
				   b->stk[j].lineno != stk[j].lineno ||
				   !__go_strings_equal(b->stk[j].filename, stk[j].filename))
					break;
			}
			if (j == nstk)
				return b;
		}
	}

	if(!alloc)
		return nil;

	b = runtime_persistentalloc(sizeof *b + nstk*sizeof stk[0], 0, &mstats.buckhash_sys);
	bucketmem += sizeof *b + nstk*sizeof stk[0];
	runtime_memmove(b->stk, stk, nstk*sizeof stk[0]);
	b->typ = typ;
	b->hash = h;
	b->size = size;
	b->nstk = nstk;
	b->next = buckhash[i];
	buckhash[i] = b;
	if(typ == MProf) {
		b->allnext = mbuckets;
		mbuckets = b;
	} else {
		b->allnext = bbuckets;
		bbuckets = b;
	}
	return b;
}

static void
MProf_GC(void)
{
	Bucket *b;

	for(b=mbuckets; b; b=b->allnext) {
		b->allocs += b->prev_allocs;
		b->frees += b->prev_frees;
		b->alloc_bytes += b->prev_alloc_bytes;
		b->free_bytes += b->prev_free_bytes;

		b->prev_allocs = b->recent_allocs;
		b->prev_frees = b->recent_frees;
		b->prev_alloc_bytes = b->recent_alloc_bytes;
		b->prev_free_bytes = b->recent_free_bytes;

		b->recent_allocs = 0;
		b->recent_frees = 0;
		b->recent_alloc_bytes = 0;
		b->recent_free_bytes = 0;
	}
}

// Record that a gc just happened: all the 'recent' statistics are now real.
void
runtime_MProf_GC(void)
{
	runtime_lock(&proflock);
	MProf_GC();
	runtime_unlock(&proflock);
}

static const char*
typeinfoname(int32 typeinfo)
{
	if(typeinfo == TypeInfo_SingleObject)
		return "single object";
	else if(typeinfo == TypeInfo_Array)
		return "array";
	else if(typeinfo == TypeInfo_Chan)
		return "channel";
	// runtime_throw("typinfoname: unknown type info");
	return "unknown";
}

static void
printstackframes(Location *stk, int32 nstk)
{
	Location *loc;
	int32 frame;

	for(frame = 0; frame < nstk; frame++) {
		loc = &stk[frame];
		if (loc->function.len > 0) {
			runtime_printf("\t#%d %p %S %S:%d\n", frame, loc->pc, loc->function, loc->filename, (int32)loc->lineno);
		} else {
			runtime_printf("\t#%d %p\n", frame, loc->pc);
		}
	}
}

// Called by collector to report a gc in allocfreetrace mode.
void
runtime_MProf_TraceGC(void)
{
	Location stk[32];
	int32 nstk;

	nstk = runtime_callers(1, stk, nelem(stk));
	runtime_printf("MProf_TraceGC\n");
	printstackframes(stk, nstk);
}

// Called by malloc to record a profiled block.
void
runtime_MProf_Malloc(void *p, uintptr size, uintptr typ)
{
	Location stk[32];
	Bucket *b;
	Type *type;
	const char *name;
	int32 nstk;

	nstk = runtime_callers(1, stk, nelem(stk));
	runtime_lock(&proflock);
	if(runtime_debug.allocfreetrace) {
		type = (Type*)(typ & ~3);
		name = typeinfoname(typ & 3);
		runtime_printf("MProf_Malloc(p=%p, size=%p, type=%p <%s", p, size, type, name);
		if(type != nil)
			runtime_printf(" of %S", *type->__reflection);
		runtime_printf(">)\n");
		printstackframes(stk, nstk);
	}
	b = stkbucket(MProf, size, stk, nstk, true);
	b->recent_allocs++;
	b->recent_alloc_bytes += size;
	runtime_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.
	runtime_setprofilebucket(p, b);
}

// Called when freeing a profiled block.
void
runtime_MProf_Free(Bucket *b, void *p, uintptr size, bool freed)
{
	runtime_lock(&proflock);
	if(freed) {
		b->recent_frees++;
		b->recent_free_bytes += size;
	} else {
		b->prev_frees++;
		b->prev_free_bytes += size;
	}
	if(runtime_debug.allocfreetrace) {
		runtime_printf("MProf_Free(p=%p, size=%p)\n", p, size);
		printstackframes(b->stk, b->nstk);
	}
	runtime_unlock(&proflock);
}

int64 runtime_blockprofilerate;  // in CPU ticks

void runtime_SetBlockProfileRate(intgo) __asm__ (GOSYM_PREFIX "runtime.SetBlockProfileRate");

void
runtime_SetBlockProfileRate(intgo rate)
{
	int64 r;

	if(rate <= 0)
		r = 0;  // disable profiling
	else {
		// convert ns to cycles, use float64 to prevent overflow during multiplication
		r = (float64)rate*runtime_tickspersecond()/(1000*1000*1000);
		if(r == 0)
			r = 1;
	}
	runtime_atomicstore64((uint64*)&runtime_blockprofilerate, r);
}

void
runtime_blockevent(int64 cycles, int32 skip)
{
	int32 nstk;
	int64 rate;
	Location stk[32];
	Bucket *b;

	if(cycles <= 0)
		return;
	rate = runtime_atomicload64((uint64*)&runtime_blockprofilerate);
	if(rate <= 0 || (rate > cycles && runtime_fastrand1()%rate > cycles))
		return;

	nstk = runtime_callers(skip, stk, nelem(stk));
	runtime_lock(&proflock);
	b = stkbucket(BProf, 0, stk, nstk, true);
	b->count++;
	b->cycles += cycles;
	runtime_unlock(&proflock);
}

// Go interface to profile data.  (Declared in debug.go)

// Must match MemProfileRecord in debug.go.
typedef struct Record Record;
struct Record {
	int64 alloc_bytes, free_bytes;
	int64 alloc_objects, free_objects;
	uintptr stk[32];
};

// Write b's data to r.
static void
record(Record *r, Bucket *b)
{
	uint32 i;

	r->alloc_bytes = b->alloc_bytes;
	r->free_bytes = b->free_bytes;
	r->alloc_objects = b->allocs;
	r->free_objects = b->frees;
	for(i=0; i<b->nstk && i<nelem(r->stk); i++)
		r->stk[i] = b->stk[i].pc;
	for(; i<nelem(r->stk); i++)
		r->stk[i] = 0;
}

func MemProfile(p Slice, include_inuse_zero bool) (n int, ok bool) {
	Bucket *b;
	Record *r;
	bool clear;

	runtime_lock(&proflock);
	n = 0;
	clear = true;
	for(b=mbuckets; b; b=b->allnext) {
		if(include_inuse_zero || b->alloc_bytes != b->free_bytes)
			n++;
		if(b->allocs != 0 || b->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; b=b->allnext)
			if(include_inuse_zero || b->alloc_bytes != b->free_bytes)
				n++;
	}
	ok = false;
	if(n <= p.__count) {
		ok = true;
		r = (Record*)p.__values;
		for(b=mbuckets; b; b=b->allnext)
			if(include_inuse_zero || b->alloc_bytes != b->free_bytes)
				record(r++, b);
	}
	runtime_unlock(&proflock);
}

void
runtime_MProf_Mark(struct Workbuf **wbufp, void (*enqueue1)(struct Workbuf**, Obj))
{
	// buckhash is not allocated via mallocgc.
	enqueue1(wbufp, (Obj){(byte*)&mbuckets, sizeof mbuckets, 0});
	enqueue1(wbufp, (Obj){(byte*)&bbuckets, sizeof bbuckets, 0});
}

// Must match BlockProfileRecord in debug.go.
typedef struct BRecord BRecord;
struct BRecord {
	int64 count;
	int64 cycles;
	uintptr stk[32];
};

func BlockProfile(p Slice) (n int, ok bool) {
	Bucket *b;
	BRecord *r;
	int32 i;

	runtime_lock(&proflock);
	n = 0;
	for(b=bbuckets; b; b=b->allnext)
		n++;
	ok = false;
	if(n <= p.__count) {
		ok = true;
		r = (BRecord*)p.__values;
		for(b=bbuckets; b; b=b->allnext, r++) {
			r->count = b->count;
			r->cycles = b->cycles;
			for(i=0; (uintptr)i<b->nstk && (uintptr)i<nelem(r->stk); i++)
				r->stk[i] = b->stk[i].pc;
			for(; (uintptr)i<nelem(r->stk); i++)
				r->stk[i] = 0;			
		}
	}
	runtime_unlock(&proflock);
}

// Must match StackRecord in debug.go.
typedef struct TRecord TRecord;
struct TRecord {
	uintptr stk[32];
};

func ThreadCreateProfile(p Slice) (n int, ok bool) {
	TRecord *r;
	M *first, *mp;
	int32 i;
	
	first = runtime_atomicloadp(&runtime_allm);
	n = 0;
	for(mp=first; mp; mp=mp->alllink)
		n++;
	ok = false;
	if(n <= p.__count) {
		ok = true;
		r = (TRecord*)p.__values;
		for(mp=first; mp; mp=mp->alllink) {
			for(i = 0; (uintptr)i < nelem(r->stk); i++) {
				r->stk[i] = mp->createstack[i].pc;
			}
			r++;
		}
	}
}

func Stack(b Slice, all bool) (n int) {
	byte *pc, *sp;
	bool enablegc;
	
	sp = runtime_getcallersp(&b);
	pc = (byte*)(uintptr)runtime_getcallerpc(&b);

	if(all) {
		runtime_semacquire(&runtime_worldsema, false);
		runtime_m()->gcing = 1;
		runtime_stoptheworld();
		enablegc = mstats.enablegc;
		mstats.enablegc = false;
	}

	if(b.__count == 0)
		n = 0;
	else{
		G* g = runtime_g();
		g->writebuf = (byte*)b.__values;
		g->writenbuf = b.__count;
		USED(pc);
		USED(sp);
		runtime_goroutineheader(g);
		runtime_traceback();
		runtime_printcreatedby(g);
		if(all)
			runtime_tracebackothers(g);
		n = b.__count - g->writenbuf;
		g->writebuf = nil;
		g->writenbuf = 0;
	}
	
	if(all) {
		runtime_m()->gcing = 0;
		mstats.enablegc = enablegc;
		runtime_semrelease(&runtime_worldsema);
		runtime_starttheworld();
	}
}

static void
saveg(G *gp, TRecord *r)
{
	int32 n, i;
	Location locstk[nelem(r->stk)];

	if(gp == runtime_g()) {
		n = runtime_callers(0, locstk, nelem(r->stk));
		for(i = 0; i < n; i++)
			r->stk[i] = locstk[i].pc;
	}
	else {
		// FIXME: Not implemented.
		n = 0;
	}
	if((size_t)n < nelem(r->stk))
		r->stk[n] = 0;
}

func GoroutineProfile(b Slice) (n int, ok bool) {
	uintptr i;
	TRecord *r;
	G *gp;
	
	ok = false;
	n = runtime_gcount();
	if(n <= b.__count) {
		runtime_semacquire(&runtime_worldsema, false);
		runtime_m()->gcing = 1;
		runtime_stoptheworld();

		n = runtime_gcount();
		if(n <= b.__count) {
			G* g = runtime_g();
			ok = true;
			r = (TRecord*)b.__values;
			saveg(g, r++);
			for(i = 0; i < runtime_allglen; i++) {
				gp = runtime_allg[i];
				if(gp == g || gp->status == Gdead)
					continue;
				saveg(gp, r++);
			}
		}
	
		runtime_m()->gcing = 0;
		runtime_semrelease(&runtime_worldsema);
		runtime_starttheworld();
	}
}