1 files changed, 361 insertions, 0 deletions
diff --git a/src/runtime/mheap.c b/src/runtime/mheap.c
new file mode 100644
index 000000000..9c6de16af
--- /dev/null
+++ b/src/runtime/mheap.c
@@ -0,0 +1,361 @@
+// 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.
+
+// Page heap.
+//
+// See malloc.h for overview.
+//
+// When a MSpan is in the heap free list, state == MSpanFree
+// and heapmap(s->start) == span, heapmap(s->start+s->npages-1) == span.
+//
+// When a MSpan is allocated, state == MSpanInUse
+// and heapmap(i) == span for all s->start <= i < s->start+s->npages.
+
+#include "runtime.h"
+#include "malloc.h"
+
+static MSpan *MHeap_AllocLocked(MHeap*, uintptr, int32);
+static bool MHeap_Grow(MHeap*, uintptr);
+static void MHeap_FreeLocked(MHeap*, MSpan*);
+static MSpan *MHeap_AllocLarge(MHeap*, uintptr);
+static MSpan *BestFit(MSpan*, uintptr, MSpan*);
+
+// Initialize the heap; fetch memory using alloc.
+void
+MHeap_Init(MHeap *h, void *(*alloc)(uintptr))
+{
+	int32 i;
+
+	FixAlloc_Init(&h->spanalloc, sizeof(MSpan), alloc);
+	FixAlloc_Init(&h->cachealloc, sizeof(MCache), alloc);
+	MHeapMap_Init(&h->map, alloc);
+	// h->mapcache needs no init
+	for(i=0; i<nelem(h->free); i++)
+		MSpanList_Init(&h->free[i]);
+	MSpanList_Init(&h->large);
+	for(i=0; i<nelem(h->central); i++)
+		MCentral_Init(&h->central[i], i);
+}
+
+// Allocate a new span of npage pages from the heap
+// and record its size class in the HeapMap and HeapMapCache.
+MSpan*
+MHeap_Alloc(MHeap *h, uintptr npage, int32 sizeclass)
+{
+	MSpan *s;
+
+	lock(h);
+	s = MHeap_AllocLocked(h, npage, sizeclass);
+	unlock(h);
+	return s;
+}
+
+static MSpan*
+MHeap_AllocLocked(MHeap *h, uintptr npage, int32 sizeclass)
+{
+	uintptr n;
+	MSpan *s, *t;
+
+	// Try in fixed-size lists up to max.
+	for(n=npage; n < nelem(h->free); n++) {
+		if(!MSpanList_IsEmpty(&h->free[n])) {
+			s = h->free[n].next;
+			goto HaveSpan;
+		}
+	}
+
+	// Best fit in list of large spans.
+	if((s = MHeap_AllocLarge(h, npage)) == nil) {
+		if(!MHeap_Grow(h, npage))
+			return nil;
+		if((s = MHeap_AllocLarge(h, npage)) == nil)
+			return nil;
+	}
+
+HaveSpan:
+	// Mark span in use.
+	if(s->state != MSpanFree)
+		throw("MHeap_AllocLocked - MSpan not free");
+	if(s->npages < npage)
+		throw("MHeap_AllocLocked - bad npages");
+	MSpanList_Remove(s);
+	s->state = MSpanInUse;
+
+	if(s->npages > npage) {
+		// Trim extra and put it back in the heap.
+		t = FixAlloc_Alloc(&h->spanalloc);
+		MSpan_Init(t, s->start + npage, s->npages - npage);
+		s->npages = npage;
+		MHeapMap_Set(&h->map, t->start - 1, s);
+		MHeapMap_Set(&h->map, t->start, t);
+		MHeapMap_Set(&h->map, t->start + t->npages - 1, t);
+		t->state = MSpanInUse;
+		MHeap_FreeLocked(h, t);
+	}
+
+	// If span is being used for small objects, cache size class.
+	// No matter what, cache span info, because gc needs to be
+	// able to map interior pointer to containing span.
+	s->sizeclass = sizeclass;
+	for(n=0; n<npage; n++) {
+		MHeapMap_Set(&h->map, s->start+n, s);
+		if(sizeclass != 0)
+			MHeapMapCache_SET(&h->mapcache, s->start+n, sizeclass);
+	}
+
+	return s;
+}
+
+// Allocate a span of exactly npage pages from the list of large spans.
+static MSpan*
+MHeap_AllocLarge(MHeap *h, uintptr npage)
+{
+	return BestFit(&h->large, npage, nil);
+}
+
+// Search list for smallest span with >= npage pages.
+// If there are multiple smallest spans, take the one
+// with the earliest starting address.
+static MSpan*
+BestFit(MSpan *list, uintptr npage, MSpan *best)
+{
+	MSpan *s;
+
+	for(s=list->next; s != list; s=s->next) {
+		if(s->npages < npage)
+			continue;
+		if(best == nil
+		|| s->npages < best->npages
+		|| (s->npages == best->npages && s->start < best->start))
+			best = s;
+	}
+	return best;
+}
+
+// Try to add at least npage pages of memory to the heap,
+// returning whether it worked.
+static bool
+MHeap_Grow(MHeap *h, uintptr npage)
+{
+	uintptr ask;
+	void *v;
+	MSpan *s;
+
+	// Ask for a big chunk, to reduce the number of mappings
+	// the operating system needs to track; also amortizes
+	// the overhead of an operating system mapping.
+	ask = npage<<PageShift;
+	if(ask < HeapAllocChunk)
+		ask = HeapAllocChunk;
+
+	v = SysAlloc(ask);
+	if(v == nil) {
+		if(ask > (npage<<PageShift)) {
+			ask = npage<<PageShift;
+			v = SysAlloc(ask);
+		}
+		if(v == nil)
+			return false;
+	}
+
+	// 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.)
+
+	if(!MHeapMap_Preallocate(&h->map, ((uintptr)v>>PageShift) - 1, (ask>>PageShift) + 2)) {
+		SysFree(v, ask);
+		return false;
+	}
+
+	s = FixAlloc_Alloc(&h->spanalloc);
+	MSpan_Init(s, (uintptr)v>>PageShift, ask>>PageShift);
+	MHeapMap_Set(&h->map, s->start, s);
+	MHeapMap_Set(&h->map, s->start + s->npages - 1, s);
+	s->state = MSpanInUse;
+	MHeap_FreeLocked(h, s);
+	return true;
+}
+
+// Look up the span at the given page number.
+MSpan*
+MHeap_Lookup(MHeap *h, PageID p)
+{
+	return MHeapMap_Get(&h->map, p);
+}
+
+// Free the span back into the heap.
+void
+MHeap_Free(MHeap *h, MSpan *s)
+{
+	lock(h);
+	MHeap_FreeLocked(h, s);
+	unlock(h);
+}
+
+static void
+MHeap_FreeLocked(MHeap *h, MSpan *s)
+{
+	MSpan *t;
+
+	if(s->state != MSpanInUse || s->ref != 0)
+		throw("MHeap_FreeLocked - invalid free");
+	s->state = MSpanFree;
+	MSpanList_Remove(s);
+
+	// Coalesce with earlier, later spans.
+	if((t = MHeapMap_Get(&h->map, s->start - 1)) != nil && t->state != MSpanInUse) {
+		s->start = t->start;
+		s->npages += t->npages;
+		MHeapMap_Set(&h->map, s->start, s);
+		MSpanList_Remove(t);
+		FixAlloc_Free(&h->spanalloc, t);
+	}
+	if((t = MHeapMap_Get(&h->map, s->start + s->npages)) != nil && t->state != MSpanInUse) {
+		s->npages += t->npages;
+		MHeapMap_Set(&h->map, s->start + s->npages - 1, s);
+		MSpanList_Remove(t);
+		FixAlloc_Free(&h->spanalloc, t);
+	}
+
+	// Insert s into appropriate list.
+	if(s->npages < nelem(h->free))
+		MSpanList_Insert(&h->free[s->npages], s);
+	else
+		MSpanList_Insert(&h->large, s);
+
+	// TODO(rsc): IncrementalScavenge() to return memory to OS.
+}
+
+// 3-level radix tree mapping page ids to Span*.
+void
+MHeapMap_Init(MHeapMap *m, void *(*allocator)(size_t))
+{
+	m->allocator = allocator;
+}
+
+MSpan*
+MHeapMap_Get(MHeapMap *m, PageID k)
+{
+	int32 i1, i2, i3;
+
+	i3 = k & MHeapMap_Level3Mask;
+	k >>= MHeapMap_Level3Bits;
+	i2 = k & MHeapMap_Level2Mask;
+	k >>= MHeapMap_Level2Bits;
+	i1 = k & MHeapMap_Level1Mask;
+	k >>= MHeapMap_Level1Bits;
+	if(k != 0)
+		throw("MHeapMap_Get");
+
+	return m->p[i1]->p[i2]->s[i3];
+}
+
+void
+MHeapMap_Set(MHeapMap *m, PageID k, MSpan *s)
+{
+	int32 i1, i2, i3;
+
+	i3 = k & MHeapMap_Level3Mask;
+	k >>= MHeapMap_Level3Bits;
+	i2 = k & MHeapMap_Level2Mask;
+	k >>= MHeapMap_Level2Bits;
+	i1 = k & MHeapMap_Level1Mask;
+	k >>= MHeapMap_Level1Bits;
+	if(k != 0)
+		throw("MHeapMap_Set");
+
+	m->p[i1]->p[i2]->s[i3] = s;
+}
+
+// Allocate the storage required for entries [k, k+1, ..., k+len-1]
+// so that Get and Set calls need not check for nil pointers.
+bool
+MHeapMap_Preallocate(MHeapMap *m, PageID k, uintptr len)
+{
+	uintptr end;
+	int32 i1, i2;
+	MHeapMapNode2 *p2;
+	MHeapMapNode3 *p3;
+
+	end = k+len;
+	while(k < end) {
+		if((k >> MHeapMap_TotalBits) != 0)
+			return false;
+		i2 = (k >> MHeapMap_Level3Bits) & MHeapMap_Level2Mask;
+		i1 = (k >> (MHeapMap_Level3Bits + MHeapMap_Level2Bits)) & MHeapMap_Level1Mask;
+
+		// first-level pointer
+		if((p2 = m->p[i1]) == nil) {
+			p2 = m->allocator(sizeof *p2);
+			if(p2 == nil)
+				return false;
+			sys·memclr((byte*)p2, sizeof *p2);
+			m->p[i1] = p2;
+		}
+
+		// second-level pointer
+		if(p2->p[i2] == nil) {
+			p3 = m->allocator(sizeof *p3);
+			if(p3 == nil)
+				return false;
+			sys·memclr((byte*)p3, sizeof *p3);
+			p2->p[i2] = p3;
+		}
+
+		// advance key past this leaf node
+		k = ((k >> MHeapMap_Level3Bits) + 1) << MHeapMap_Level3Bits;
+	}
+	return true;
+}
+
+// Initialize a new span with the given start and npages.
+void
+MSpan_Init(MSpan *span, PageID start, uintptr npages)
+{
+	span->next = nil;
+	span->prev = nil;
+	span->start = start;
+	span->npages = npages;
+	span->freelist = nil;
+	span->ref = 0;
+	span->sizeclass = 0;
+	span->state = 0;
+}
+
+// Initialize an empty doubly-linked list.
+void
+MSpanList_Init(MSpan *list)
+{
+	list->next = list;
+	list->prev = list;
+}
+
+void
+MSpanList_Remove(MSpan *span)
+{
+	if(span->prev == nil && span->next == nil)
+		return;
+	span->prev->next = span->next;
+	span->next->prev = span->prev;
+	span->prev = nil;
+	span->next = nil;
+}
+
+bool
+MSpanList_IsEmpty(MSpan *list)
+{
+	return list->next == list;
+}
+
+void
+MSpanList_Insert(MSpan *list, MSpan *span)
+{
+	if(span->next != nil || span->prev != nil)
+		throw("MSpanList_Insert");
+	span->next = list->next;
+	span->prev = list;
+	span->next->prev = span;
+	span->prev->next = span;
+}
+