runtime: malloc fixes

  * throw away dead code
  * add mlookup counter
  * add malloc counter
  * set up for blocks with no pointers

Fixes #367.

R=r
https://golang.org/cl/165050

src/pkg/malloc/malloc.go

@@ -17,6 +17,8 @@ type Stats struct {
 	Stacks		uint64;
 	InusePages	uint64;
 	NextGC		uint64;
+	Lookups		uint64;
+	Mallocs		uint64;
 	EnableGC	bool;
 }
 

src/pkg/runtime/iface.c

@@ -590,12 +590,12 @@ unsafe·Reflect(Eface e, Eface rettype, void *retaddr)
 
 			// but then build pointer to x so that Reflect
 			// always returns pointer to data.
-			p = mallocgc(sizeof(uintptr));
+			p = mal(sizeof(uintptr));
 			*p = x;
 		} else {
 			// Already a pointer, but still make a copy,
 			// to preserve value semantics for interface data.
-			p = mallocgc(e.type->size);
+			p = mal(e.type->size);
 			algarray[e.type->alg].copy(e.type->size, p, e.data);
 		}
 		retaddr = p;

src/pkg/runtime/malloc.cgo

@@ -5,7 +5,6 @@
 // See malloc.h for overview.
 //
 // TODO(rsc): double-check stats.
-// TODO(rsc): solve "stack overflow during malloc" problem.
 
 package malloc
 #include "runtime.h"
@@ -19,7 +18,7 @@ MStats mstats;
 // Small objects are allocated from the per-thread cache's free lists.
 // Large objects (> 32 kB) are allocated straight from the heap.
 void*
-malloc(uintptr size)
+mallocgc(uintptr size, uint32 refflag, int32 dogc)
 {
 	int32 sizeclass;
 	MCache *c;
@@ -35,6 +34,7 @@ malloc(uintptr size)
 	if(size == 0)
 		size = 1;
 
+	mstats.nmalloc++;
 	if(size <= MaxSmallSize) {
 		// Allocate from mcache free lists.
 		sizeclass = SizeToClass(size);
@@ -63,21 +63,19 @@ malloc(uintptr size)
 		printf("malloc %D; mlookup failed\n", (uint64)size);
 		throw("malloc mlookup");
 	}
-	*ref = RefNone;
+	*ref = RefNone | refflag;
 
 	m->mallocing = 0;
+
+	if(dogc && mstats.inuse_pages > mstats.next_gc)
+		gc(0);
 	return v;
 }
 
 void*
-mallocgc(uintptr size)
+malloc(uintptr size)
 {
-	void *v;
-
-	v = malloc(size);
-	if(mstats.inuse_pages > mstats.next_gc)
-		gc(0);
-	return v;
+	return mallocgc(size, 0, 0);
 }
 
 // Free the object whose base pointer is v.
@@ -138,6 +136,7 @@ mlookup(void *v, byte **base, uintptr *size, uint32 **ref)
 	byte *p;
 	MSpan *s;
 
+	mstats.nlookup++;
 	s = MHeap_LookupMaybe(&mheap, (uintptr)v>>PageShift);
 	if(s == nil) {
 		if(base)
@@ -209,6 +208,7 @@ void*
 SysAlloc(uintptr n)
 {
 	void *p;
+
 	mstats.sys += n;
 	p = runtime_mmap(nil, n, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_ANON|MAP_PRIVATE, -1, 0);
 	if(p < (void*)4096) {
@@ -241,30 +241,10 @@ SysFree(void *v, uintptr n)
 
 // Runtime stubs.
 
-extern void *oldmal(uint32);
-
 void*
 mal(uint32 n)
 {
-//return oldmal(n);
-	void *v;
-
-	v = mallocgc(n);
-
-	if(0) {
-		byte *p;
-		uint32 i;
-		p = v;
-		for(i=0; i<n; i++) {
-			if(p[i] != 0) {
-				printf("mal %d => %p: byte %d is non-zero\n", n, v, i);
-				throw("mal");
-			}
-		}
-	}
-
-//printf("mal %d %p\n", n, v);  // |checkmal to check for overlapping returns.
-	return v;
+	return mallocgc(n, 0, 1);
 }
 
 // Stack allocator uses malloc/free most of the time,
@@ -285,7 +265,6 @@ stackalloc(uint32 n)
 	void *v;
 	uint32 *ref;
 
-//return oldmal(n);
 	if(m->mallocing || m->gcing) {
 		lock(&stacks);
 		if(stacks.size == 0)
@@ -308,8 +287,6 @@ stackalloc(uint32 n)
 void
 stackfree(void *v)
 {
-//return;
-
 	if(m->mallocing || m->gcing) {
 		lock(&stacks);
 		FixAlloc_Free(&stacks, v);

src/pkg/runtime/malloc.h

@@ -163,6 +163,8 @@ struct MStats
 	uint64	stacks;
 	uint64	inuse_pages;	// protected by mheap.Lock
 	uint64	next_gc;	// protected by mheap.Lock
+	uint64	nlookup;	// unprotected (approximate)
+	uint64	nmalloc;	// unprotected (approximate)
 	bool	enablegc;
 };
 extern MStats mstats;
@@ -271,6 +273,10 @@ struct MHeap
 	// span lookup
 	MHeapMap map;
 	MHeapMapCache mapcache;
+	
+	// range of addresses we might see in the heap
+	byte *min;
+	byte *max;
 
 	// central free lists for small size classes.
 	// the union makes sure that the MCentrals are
@@ -292,6 +298,7 @@ void	MHeap_Free(MHeap *h, MSpan *s);
 MSpan*	MHeap_Lookup(MHeap *h, PageID p);
 MSpan*	MHeap_LookupMaybe(MHeap *h, PageID p);
 
+void*	mallocgc(uintptr size, uint32 flag, int32 dogc);
 int32	mlookup(void *v, byte **base, uintptr *size, uint32 **ref);
 void	gc(int32 force);
 
@@ -300,9 +307,9 @@ enum
 	RefcountOverhead = 4,	// one uint32 per object
 
 	RefFree = 0,	// must be zero
-	RefManual,	// manual allocation - don't free
 	RefStack,		// stack segment - don't free and don't scan for pointers
 	RefNone,		// no references
 	RefSome,		// some references
+	RefNoPointers = 0x80000000U,	// flag - no pointers here     
 };
 

src/pkg/runtime/mem.c

@@ -13,67 +13,6 @@ enum
 	NHUNK		= 20<<20,
 };
 
-// Convenient wrapper around mmap.
-static void*
-brk(uint32 n)
-{
-	byte *v;
-
-	v = runtime_mmap(nil, n, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_ANON|MAP_PRIVATE, 0, 0);
-	if(v < (void *)4096) {
-		printf("mmap: errno=%p\n", v);
-		exit(2);
-	}
-	m->mem.nmmap += n;
-	return v;
-}
-
-// Allocate n bytes of memory.  Note that this gets used
-// to allocate new stack segments, so at each call to a function
-// you have to ask yourself "would it be okay to call mal recursively
-// right here?"  The answer is yes unless we're in the middle of
-// editing the malloc state in m->mem.
-void*
-oldmal(uint32 n)
-{
-	byte* v;
-
-	// round to keep everything 64-bit aligned
-	n = rnd(n, 8);
-
-	// be careful.  calling any function might invoke
-	// mal to allocate more stack.
-	if(n > NHUNK) {
-		v = brk(n);
-	} else {
-		// allocate a new hunk if this one is too small
-		if(n > m->mem.nhunk) {
-			// here we're in the middle of editing m->mem
-			// (we're about to overwrite m->mem.hunk),
-			// so we can't call brk - it might call mal to grow the
-			// stack, and the recursive call would allocate a new
-			// hunk, and then once brk returned we'd immediately
-			// overwrite that hunk with our own.
-			// (the net result would be a memory leak, not a crash.)
-			// so we have to call runtime_mmap directly - it is written
-			// in assembly and tagged not to grow the stack.
-			m->mem.hunk =
-				runtime_mmap(nil, NHUNK, PROT_READ|PROT_WRITE|PROT_EXEC,
-					MAP_ANON|MAP_PRIVATE, 0, 0);
-			if(m->mem.hunk < (void*)4096) {
-				*(uint32*)0xf1 = 0;
-			}
-			m->mem.nhunk = NHUNK;
-			m->mem.nmmap += NHUNK;
-		}
-		v = m->mem.hunk;
-		m->mem.hunk += n;
-		m->mem.nhunk -= n;
-	}
-	m->mem.nmal += n;
-	return v;
-}
-
 void
 runtime·mal(uint32 n, uint8 *ret)
 {

src/pkg/runtime/mgc0.c

@@ -48,9 +48,16 @@ scanblock(int32 depth, byte *b, int64 n)
 	vp = (void**)b;
 	n /= PtrSize;
 	for(i=0; i<n; i++) {
-		if(mlookup(vp[i], &obj, &size, &ref)) {
+		obj = vp[i];
+		if(obj == nil || (byte*)obj < mheap.min || (byte*)obj >= mheap.max)
+			continue;
+		if(mlookup(obj, &obj, &size, &ref)) {
 			if(*ref == RefFree || *ref == RefStack)
 				continue;
+			if(*ref == (RefNone|RefNoPointers)) {
+				*ref = RefSome|RefNoPointers;
+				continue;
+			}
 			if(*ref == RefNone) {
 				if(Debug)
 					printf("%d found at %p: ", depth, &vp[i]);
@@ -125,15 +132,16 @@ sweepspan(MSpan *s)
 		default:
 			throw("bad 'ref count'");
 		case RefFree:
-		case RefManual:
 		case RefStack:
 			break;
 		case RefNone:
+		case RefNone|RefNoPointers:
 			if(Debug)
 				printf("free %D at %p\n", (uint64)s->npages<<PageShift, p);
 			free(p);
 			break;
 		case RefSome:
+		case RefSome|RefNoPointers:
 //printf("gc-mem 1 %D\n", (uint64)s->npages<<PageShift);
 			s->gcref0 = RefNone;	// set up for next mark phase
 			break;
@@ -151,15 +159,16 @@ sweepspan(MSpan *s)
 		default:
 			throw("bad 'ref count'");
 		case RefFree:
-		case RefManual:
 		case RefStack:
 			break;
 		case RefNone:
+		case RefNone|RefNoPointers:
 			if(Debug)
 				printf("free %d at %p\n", size, p+i*size);
 			free(p + i*size);
 			break;
 		case RefSome:
+		case RefSome|RefNoPointers:
 			s->gcref[i] = RefNone;	// set up for next mark phase
 			break;
 		}

src/pkg/runtime/mheap.c

@@ -186,6 +186,11 @@ MHeap_Grow(MHeap *h, uintptr npage)
 			return false;
 	}
 
+	if((byte*)v < h->min || h->min == nil)
+		h->min = v;
+	if((byte*)v+ask > h->max)
+		h->max = (byte*)v+ask;
+
 	// NOTE(rsc): In tcmalloc, if we've accumulated enough
 	// system allocations, the heap map gets entirely allocated
 	// in 32-bit mode.  (In 64-bit mode that's not practical.)

src/pkg/runtime/runtime.h

@@ -175,13 +175,6 @@ struct	G
 	void	(*cgofn)(void*);	// for cgo/ffi
 	void	*cgoarg;
 };
-struct	Mem
-{
-	uint8*	hunk;
-	uint32	nhunk;
-	uint64	nmmap;
-	uint64	nmal;
-};
 struct	M
 {
 	// The offsets of these fields are known to (hard-coded in) libmach.
@@ -208,7 +201,6 @@ struct	M
 	G*	nextg;
 	M*	alllink;	// on allm
 	M*	schedlink;
-	Mem	mem;
 	uint32	machport;	// Return address for Mach IPC (OS X)
 	MCache	*mcache;
 	G*	lockedg;
@@ -375,7 +367,6 @@ uintptr	efacehash(Eface);
 uintptr	nohash(uint32, void*);
 uint32	noequal(uint32, void*, void*);
 void*	malloc(uintptr size);
-void*	mallocgc(uintptr size);
 void	free(void *v);
 void	exit(int32);
 void	breakpoint(void);