runtime: faster allocator, garbage collector

GC is still single-threaded.
Multiple threads will happen in another CL.

Garbage collection pauses are typically
about half as long as they were before this CL.

R=brainman, iant, r
CC=golang-dev
https://golang.org/cl/3975046

src/pkg/runtime/debug.go

@@ -69,7 +69,8 @@ type MemStatsType struct {
 
 	// Per-size allocation statistics.
 	// Not locked during update; approximate.
-	BySize [67]struct {
+	// 61 is NumSizeClasses in the C code.
+	BySize [61]struct {
 		Size    uint32
 		Mallocs uint64
 		Frees   uint64

src/pkg/runtime/iface.c

@@ -702,7 +702,7 @@ unsafe·New(Eface typ, void *ret)
 	t = (Type*)((Eface*)typ.data-1);
 
 	if(t->kind&KindNoPointers)
-		ret = runtime·mallocgc(t->size, RefNoPointers, 1, 1);
+		ret = runtime·mallocgc(t->size, FlagNoPointers, 1, 1);
 	else
 		ret = runtime·mal(t->size);
 	FLUSH(&ret);
@@ -722,7 +722,7 @@ unsafe·NewArray(Eface typ, uint32 n, void *ret)
 	
 	size = n*t->size;
 	if(t->kind&KindNoPointers)
-		ret = runtime·mallocgc(size, RefNoPointers, 1, 1);
+		ret = runtime·mallocgc(size, FlagNoPointers, 1, 1);
 	else
 		ret = runtime·mal(size);
 	FLUSH(&ret);

src/pkg/runtime/malloc.h

@@ -97,8 +97,14 @@ typedef	uintptr	PageID;		// address >> PageShift
 
 enum
 {
+	// Computed constant.  The definition of MaxSmallSize and the
+	// algorithm in msize.c produce some number of different allocation
+	// size classes.  NumSizeClasses is that number.  It's needed here
+	// because there are static arrays of this length; when msize runs its
+	// size choosing algorithm it double-checks that NumSizeClasses agrees.
+	NumSizeClasses = 61,
+
 	// Tunable constants.
-	NumSizeClasses = 67,		// Number of size classes (must match msize.c)
 	MaxSmallSize = 32<<10,
 
 	FixAllocChunk = 128<<10,	// Chunk size for FixAlloc
@@ -290,10 +296,7 @@ struct MSpan
 	uint32	ref;		// number of allocated objects in this span
 	uint32	sizeclass;	// size class
 	uint32	state;		// MSpanInUse etc
-	union {
-		uint32	*gcref;	// sizeclass > 0
-		uint32	gcref0;	// sizeclass == 0
-	};
+	byte	*limit;	// end of data in span
 };
 
 void	runtime·MSpan_Init(MSpan *span, PageID start, uintptr npages);
@@ -336,6 +339,7 @@ struct MHeap
 
 	// range of addresses we might see in the heap
 	byte *bitmap;
+	uintptr bitmap_mapped;
 	byte *arena_start;
 	byte *arena_used;
 	byte *arena_end;
@@ -359,26 +363,29 @@ MSpan*	runtime·MHeap_Alloc(MHeap *h, uintptr npage, int32 sizeclass, int32 acct
 void	runtime·MHeap_Free(MHeap *h, MSpan *s, int32 acct);
 MSpan*	runtime·MHeap_Lookup(MHeap *h, void *v);
 MSpan*	runtime·MHeap_LookupMaybe(MHeap *h, void *v);
-void	runtime·MGetSizeClassInfo(int32 sizeclass, int32 *size, int32 *npages, int32 *nobj);
+void	runtime·MGetSizeClassInfo(int32 sizeclass, uintptr *size, int32 *npages, int32 *nobj);
 void*	runtime·MHeap_SysAlloc(MHeap *h, uintptr n);
+void	runtime·MHeap_MapBits(MHeap *h);
 
 void*	runtime·mallocgc(uintptr size, uint32 flag, int32 dogc, int32 zeroed);
-int32	runtime·mlookup(void *v, byte **base, uintptr *size, MSpan **s, uint32 **ref);
+int32	runtime·mlookup(void *v, byte **base, uintptr *size, MSpan **s);
 void	runtime·gc(int32 force);
+void	runtime·markallocated(void *v, uintptr n, bool noptr);
+void	runtime·checkallocated(void *v, uintptr n);
+void	runtime·markfreed(void *v, uintptr n);
+void	runtime·checkfreed(void *v, uintptr n);
+int32	runtime·checking;
+void	runtime·markspan(void *v, uintptr size, uintptr n, bool leftover);
+void	runtime·unmarkspan(void *v, uintptr size);
+bool	runtime·blockspecial(void*);
+void	runtime·setblockspecial(void*);
 
 enum
 {
-	RefcountOverhead = 4,	// one uint32 per object
-
-	RefFree = 0,	// must be zero
-	RefStack,		// stack segment - don't free and don't scan for pointers
-	RefNone,		// no references
-	RefSome,		// some references
-	RefNoPointers = 0x80000000U,	// flag - no pointers here
-	RefHasFinalizer = 0x40000000U,	// flag - has finalizer
-	RefProfiled = 0x20000000U,	// flag - is in profiling table
-	RefNoProfiling = 0x10000000U,	// flag - must not profile
-	RefFlags = 0xFFFF0000U,
+	// flags to malloc
+	FlagNoPointers = 1<<0,	// no pointers here
+	FlagNoProfiling = 1<<1,	// must not profile
+	FlagNoGC = 1<<2,	// must not free or scan for pointers
 };
 
 void	runtime·MProf_Malloc(void*, uintptr);

src/pkg/runtime/mcentral.c

@@ -113,8 +113,7 @@ static void
 MCentral_Free(MCentral *c, void *v)
 {
 	MSpan *s;
-	PageID page;
-	MLink *p, *next;
+	MLink *p;
 	int32 size;
 
 	// Find span for v.
@@ -138,16 +137,8 @@ MCentral_Free(MCentral *c, void *v)
 	if(--s->ref == 0) {
 		size = runtime·class_to_size[c->sizeclass];
 		runtime·MSpanList_Remove(s);
-		// The second word of each freed block indicates
-		// whether it needs to be zeroed.  The first word
-		// is the link pointer and must always be cleared.
-		for(p=s->freelist; p; p=next) {
-			next = p->next;
-			if(size > sizeof(uintptr) && ((uintptr*)p)[1] != 0)
-				runtime·memclr((byte*)p, size);
-			else
-				p->next = nil;
-		}
+		runtime·unmarkspan((byte*)(s->start<<PageShift), s->npages<<PageShift);
+		*(uintptr*)(s->start<<PageShift) = 1;  // needs zeroing
 		s->freelist = nil;
 		c->nfree -= (s->npages << PageShift) / size;
 		runtime·unlock(c);
@@ -157,7 +148,7 @@ MCentral_Free(MCentral *c, void *v)
 }
 
 void
-runtime·MGetSizeClassInfo(int32 sizeclass, int32 *sizep, int32 *npagesp, int32 *nobj)
+runtime·MGetSizeClassInfo(int32 sizeclass, uintptr *sizep, int32 *npagesp, int32 *nobj)
 {
 	int32 size;
 	int32 npages;
@@ -166,7 +157,7 @@ runtime·MGetSizeClassInfo(int32 sizeclass, int32 *sizep, int32 *npagesp, int32
 	size = runtime·class_to_size[sizeclass];
 	*npagesp = npages;
 	*sizep = size;
-	*nobj = (npages << PageShift) / (size + RefcountOverhead);
+	*nobj = (npages << PageShift) / size;
 }
 
 // Fetch a new span from the heap and
@@ -174,7 +165,8 @@ runtime·MGetSizeClassInfo(int32 sizeclass, int32 *sizep, int32 *npagesp, int32
 static bool
 MCentral_Grow(MCentral *c)
 {
-	int32 i, n, npages, size;
+	int32 i, n, npages;
+	uintptr size;
 	MLink **tailp, *v;
 	byte *p;
 	MSpan *s;
@@ -191,7 +183,7 @@ MCentral_Grow(MCentral *c)
 	// Carve span into sequence of blocks.
 	tailp = &s->freelist;
 	p = (byte*)(s->start << PageShift);
-	s->gcref = (uint32*)(p + size*n);
+	s->limit = p + size*n;
 	for(i=0; i<n; i++) {
 		v = (MLink*)p;
 		*tailp = v;
@@ -199,6 +191,7 @@ MCentral_Grow(MCentral *c)
 		p += size;
 	}
 	*tailp = nil;
+	runtime·markspan((byte*)(s->start<<PageShift), size, n, size*n < (s->npages<<PageShift));
 
 	runtime·lock(c);
 	c->nfree += n;

src/pkg/runtime/mfinal.c

@@ -5,6 +5,7 @@
 #include "runtime.h"
 #include "malloc.h"
 
+// TODO(rsc): Why not just use mheap.Lock?
 static Lock finlock;
 
 // Finalizer hash table.  Direct hash, linear scan, at most 3/4 full.
@@ -101,24 +102,21 @@ runtime·addfinalizer(void *p, void (*f)(void*), int32 nret)
 	}
 
 	runtime·lock(&finlock);
-	if(!runtime·mlookup(p, &base, nil, nil, &ref) || p != base) {
+	if(!runtime·mlookup(p, &base, nil, nil) || p != base) {
 		runtime·unlock(&finlock);
 		runtime·throw("addfinalizer on invalid pointer");
 	}
 	if(f == nil) {
-		if(*ref & RefHasFinalizer) {
 		lookfintab(&fintab, p, 1);
-			*ref &= ~RefHasFinalizer;
-		}
 		runtime·unlock(&finlock);
 		return;
 	}
 
-	if(*ref & RefHasFinalizer) {
+	if(lookfintab(&fintab, p, 0)) {
 		runtime·unlock(&finlock);
 		runtime·throw("double finalizer");
 	}
-	*ref |= RefHasFinalizer;
+	runtime·setblockspecial(p);
 
 	if(fintab.nkey >= fintab.max/2+fintab.max/4) {
 		// keep table at most 3/4 full:
@@ -134,7 +132,7 @@ runtime·addfinalizer(void *p, void (*f)(void*), int32 nret)
 			newtab.max *= 3;
 		}
 
-		newtab.key = runtime·mallocgc(newtab.max*sizeof newtab.key[0], RefNoPointers, 0, 1);
+		newtab.key = runtime·mallocgc(newtab.max*sizeof newtab.key[0], FlagNoPointers, 0, 1);
 		newtab.val = runtime·mallocgc(newtab.max*sizeof newtab.val[0], 0, 0, 1);
 
 		for(i=0; i<fintab.max; i++) {

src/pkg/runtime/mheap.c

@@ -180,7 +180,9 @@ MHeap_Grow(MHeap *h, uintptr npage)
 	// Allocate a multiple of 64kB (16 pages).
 	npage = (npage+15)&~15;
 	ask = npage<<PageShift;
-	if(ask < HeapAllocChunk)
+	if(ask > h->arena_end - h->arena_used)
+		return false;
+	if(ask < HeapAllocChunk && HeapAllocChunk <= h->arena_end - h->arena_used)
 		ask = HeapAllocChunk;
 
 	v = runtime·MHeap_SysAlloc(h, ask);
@@ -194,11 +196,6 @@ MHeap_Grow(MHeap *h, uintptr npage)
 	}
 	mstats.heap_sys += ask;
 
-	if((byte*)v < h->arena_start || h->arena_start == nil)
-		h->arena_start = v;
-	if((byte*)v+ask > h->arena_end)
-		h->arena_end = (byte*)v+ask;
-
 	// Create a fake "in use" span and free it, so that the
 	// right coalescing happens.
 	s = runtime·FixAlloc_Alloc(&h->spanalloc);
@@ -370,10 +367,14 @@ runtime·MSpanList_IsEmpty(MSpan *list)
 void
 runtime·MSpanList_Insert(MSpan *list, MSpan *span)
 {
-	if(span->next != nil || span->prev != nil)
+	if(span->next != nil || span->prev != nil) {
+		runtime·printf("failed MSpanList_Insert %p %p %p\n", span, span->next, span->prev);
 		runtime·throw("MSpanList_Insert");
+	}
 	span->next = list->next;
 	span->prev = list;
 	span->next->prev = span;
 	span->prev->next = span;
 }
+
+

src/pkg/runtime/mprof.goc

@@ -65,7 +65,7 @@ stkbucket(uintptr *stk, int32 nstk)
 		   runtime·mcmp((byte*)b->stk, (byte*)stk, nstk*sizeof stk[0]) == 0)
 			return b;
 
-	b = runtime·mallocgc(sizeof *b + nstk*sizeof stk[0], RefNoProfiling, 0, 1);
+	b = runtime·mallocgc(sizeof *b + nstk*sizeof stk[0], FlagNoProfiling, 0, 1);
 	bucketmem += sizeof *b + nstk*sizeof stk[0];
 	runtime·memmove(b->stk, stk, nstk*sizeof stk[0]);
 	b->hash = h;
@@ -132,7 +132,7 @@ setaddrbucket(uintptr addr, Bucket *b)
 		if(ah->addr == (addr>>20))
 			goto found;
 
-	ah = runtime·mallocgc(sizeof *ah, RefNoProfiling, 0, 1);
+	ah = runtime·mallocgc(sizeof *ah, FlagNoProfiling, 0, 1);
 	addrmem += sizeof *ah;
 	ah->next = addrhash[h];
 	ah->addr = addr>>20;
@@ -140,7 +140,7 @@ setaddrbucket(uintptr addr, Bucket *b)
 
 found:
 	if((e = addrfree) == nil) {
-		e = runtime·mallocgc(64*sizeof *e, RefNoProfiling, 0, 0);
+		e = runtime·mallocgc(64*sizeof *e, FlagNoProfiling, 0, 0);
 		addrmem += 64*sizeof *e;
 		for(i=0; i+1<64; i++)
 			e[i].next = &e[i+1];

src/pkg/runtime/msize.c

@@ -57,7 +57,7 @@ runtime·SizeToClass(int32 size)
 void
 runtime·InitSizes(void)
 {
-	int32 align, sizeclass, size, osize, nextsize, n;
+	int32 align, sizeclass, size, nextsize, n;
 	uint32 i;
 	uintptr allocsize, npages;
 
@@ -81,8 +81,7 @@ runtime·InitSizes(void)
 		// the leftover is less than 1/8 of the total,
 		// so wasted space is at most 12.5%.
 		allocsize = PageSize;
-		osize = size + RefcountOverhead;
-		while(allocsize%osize > (allocsize/8))
+		while(allocsize%size > allocsize/8)
 			allocsize += PageSize;
 		npages = allocsize >> PageShift;
 
@@ -93,7 +92,7 @@ runtime·InitSizes(void)
 		// different sizes.
 		if(sizeclass > 1
 		&& npages == runtime·class_to_allocnpages[sizeclass-1]
-		&& allocsize/osize == allocsize/(runtime·class_to_size[sizeclass-1]+RefcountOverhead)) {
+		&& allocsize/size == allocsize/runtime·class_to_size[sizeclass-1]) {
 			runtime·class_to_size[sizeclass-1] = size;
 			continue;
 		}

src/pkg/runtime/slice.c

@@ -41,7 +41,7 @@ makeslice1(SliceType *t, int32 len, int32 cap, Slice *ret)
 	ret->cap = cap;
 
 	if((t->elem->kind&KindNoPointers))
-		ret->array = runtime·mallocgc(size, RefNoPointers, 1, 1);
+		ret->array = runtime·mallocgc(size, FlagNoPointers, 1, 1);
 	else
 		ret->array = runtime·mal(size);
 }

src/pkg/runtime/string.goc

@@ -225,7 +225,7 @@ func slicebytetostring(b Slice) (s String) {
 }
 
 func stringtoslicebyte(s String) (b Slice) {
-	b.array = runtime·mallocgc(s.len, RefNoPointers, 1, 1);
+	b.array = runtime·mallocgc(s.len, FlagNoPointers, 1, 1);
 	b.len = s.len;
 	b.cap = s.len;
 	runtime·mcpy(b.array, s.str, s.len);
@@ -268,7 +268,7 @@ func stringtosliceint(s String) (b Slice) {
 		n++;
 	}
 
-	b.array = runtime·mallocgc(n*sizeof(r[0]), RefNoPointers, 1, 1);
+	b.array = runtime·mallocgc(n*sizeof(r[0]), FlagNoPointers, 1, 1);
 	b.len = n;
 	b.cap = n;
 	p = s.str;

src/pkg/runtime/windows/mem.c

@@ -48,7 +48,7 @@ runtime·SysFree(void *v, uintptr n)
 void*
 runtime·SysReserve(void *v, uintptr n)
 {
-	return runtime·stdcall(runtime·VirtualAlloc, 4, v, n, MEM_RESERVE, 0);
+	return runtime·stdcall(runtime·VirtualAlloc, 4, v, n, MEM_RESERVE, PAGE_EXECUTE_READWRITE);
 }
 
 void