1 files changed, 889 insertions, 0 deletions

diff --git a/src/runtime/mheap.c b/src/runtime/mheap.c
new file mode 100644
index 000000000..bb203d5ce
--- /dev/null
+++ b/src/runtime/mheap.c
@@ -0,0 +1,889 @@
+// 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 or MSpanStack
+// and heapmap(i) == span for all s->start <= i < s->start+s->npages.
+
+#include "runtime.h"
+#include "arch_GOARCH.h"
+#include "malloc.h"
+
+static MSpan *MHeap_AllocSpanLocked(MHeap*, uintptr);
+static void MHeap_FreeSpanLocked(MHeap*, MSpan*, bool, bool);
+static bool MHeap_Grow(MHeap*, uintptr);
+static MSpan *MHeap_AllocLarge(MHeap*, uintptr);
+static MSpan *BestFit(MSpan*, uintptr, MSpan*);
+
+static void
+RecordSpan(void *vh, byte *p)
+{
+	MHeap *h;
+	MSpan *s;
+	MSpan **all;
+	uint32 cap;
+
+	h = vh;
+	s = (MSpan*)p;
+	if(h->nspan >= h->nspancap) {
+		cap = 64*1024/sizeof(all[0]);
+		if(cap < h->nspancap*3/2)
+			cap = h->nspancap*3/2;
+		all = (MSpan**)runtime·sysAlloc(cap*sizeof(all[0]), &mstats.other_sys);
+		if(all == nil)
+			runtime·throw("runtime: cannot allocate memory");
+		if(h->allspans) {
+			runtime·memmove(all, h->allspans, h->nspancap*sizeof(all[0]));
+			// Don't free the old array if it's referenced by sweep.
+			// See the comment in mgc0.c.
+			if(h->allspans != runtime·mheap.gcspans)
+				runtime·SysFree(h->allspans, h->nspancap*sizeof(all[0]), &mstats.other_sys);
+		}
+		h->allspans = all;
+		h->nspancap = cap;
+	}
+	h->allspans[h->nspan++] = s;
+}
+
+// Initialize the heap; fetch memory using alloc.
+void
+runtime·MHeap_Init(MHeap *h)
+{
+	uint32 i;
+
+	runtime·FixAlloc_Init(&h->spanalloc, sizeof(MSpan), RecordSpan, h, &mstats.mspan_sys);
+	runtime·FixAlloc_Init(&h->cachealloc, sizeof(MCache), nil, nil, &mstats.mcache_sys);
+	runtime·FixAlloc_Init(&h->specialfinalizeralloc, sizeof(SpecialFinalizer), nil, nil, &mstats.other_sys);
+	runtime·FixAlloc_Init(&h->specialprofilealloc, sizeof(SpecialProfile), nil, nil, &mstats.other_sys);
+	// h->mapcache needs no init
+	for(i=0; i<nelem(h->free); i++) {
+		runtime·MSpanList_Init(&h->free[i]);
+		runtime·MSpanList_Init(&h->busy[i]);
+	}
+	runtime·MSpanList_Init(&h->freelarge);
+	runtime·MSpanList_Init(&h->busylarge);
+	for(i=0; i<nelem(h->central); i++)
+		runtime·MCentral_Init(&h->central[i].mcentral, i);
+}
+
+void
+runtime·MHeap_MapSpans(MHeap *h)
+{
+	uintptr n;
+
+	// Map spans array, PageSize at a time.
+	n = (uintptr)h->arena_used;
+	n -= (uintptr)h->arena_start;
+	n = n / PageSize * sizeof(h->spans[0]);
+	n = ROUND(n, PhysPageSize);
+	if(h->spans_mapped >= n)
+		return;
+	runtime·SysMap((byte*)h->spans + h->spans_mapped, n - h->spans_mapped, h->arena_reserved, &mstats.other_sys);
+	h->spans_mapped = n;
+}
+
+// Sweeps spans in list until reclaims at least npages into heap.
+// Returns the actual number of pages reclaimed.
+static uintptr
+MHeap_ReclaimList(MHeap *h, MSpan *list, uintptr npages)
+{
+	MSpan *s;
+	uintptr n;
+	uint32 sg;
+
+	n = 0;
+	sg = runtime·mheap.sweepgen;
+retry:
+	for(s = list->next; s != list; s = s->next) {
+		if(s->sweepgen == sg-2 && runtime·cas(&s->sweepgen, sg-2, sg-1)) {
+			runtime·MSpanList_Remove(s);
+			// swept spans are at the end of the list
+			runtime·MSpanList_InsertBack(list, s);
+			runtime·unlock(&h->lock);
+			n += runtime·MSpan_Sweep(s, false);
+			runtime·lock(&h->lock);
+			if(n >= npages)
+				return n;
+			// the span could have been moved elsewhere
+			goto retry;
+		}
+		if(s->sweepgen == sg-1) {
+			// the span is being sweept by background sweeper, skip
+			continue;
+		}
+		// already swept empty span,
+		// all subsequent ones must also be either swept or in process of sweeping
+		break;
+	}
+	return n;
+}
+
+// Sweeps and reclaims at least npage pages into heap.
+// Called before allocating npage pages.
+static void
+MHeap_Reclaim(MHeap *h, uintptr npage)
+{
+	uintptr reclaimed, n;
+
+	// First try to sweep busy spans with large objects of size >= npage,
+	// this has good chances of reclaiming the necessary space.
+	for(n=npage; n < nelem(h->busy); n++) {
+		if(MHeap_ReclaimList(h, &h->busy[n], npage))
+			return;  // Bingo!
+	}
+
+	// Then -- even larger objects.
+	if(MHeap_ReclaimList(h, &h->busylarge, npage))
+		return;  // Bingo!
+
+	// Now try smaller objects.
+	// One such object is not enough, so we need to reclaim several of them.
+	reclaimed = 0;
+	for(n=0; n < npage && n < nelem(h->busy); n++) {
+		reclaimed += MHeap_ReclaimList(h, &h->busy[n], npage-reclaimed);
+		if(reclaimed >= npage)
+			return;
+	}
+
+	// Now sweep everything that is not yet swept.
+	runtime·unlock(&h->lock);
+	for(;;) {
+		n = runtime·sweepone();
+		if(n == -1)  // all spans are swept
+			break;
+		reclaimed += n;
+		if(reclaimed >= npage)
+			break;
+	}
+	runtime·lock(&h->lock);
+}
+
+// Allocate a new span of npage pages from the heap for GC'd memory
+// and record its size class in the HeapMap and HeapMapCache.
+static MSpan*
+mheap_alloc(MHeap *h, uintptr npage, int32 sizeclass, bool large)
+{
+	MSpan *s;
+
+	if(g != g->m->g0)
+		runtime·throw("mheap_alloc not on M stack");
+	runtime·lock(&h->lock);
+
+	// To prevent excessive heap growth, before allocating n pages
+	// we need to sweep and reclaim at least n pages.
+	if(!h->sweepdone)
+		MHeap_Reclaim(h, npage);
+
+	// transfer stats from cache to global
+	mstats.heap_alloc += g->m->mcache->local_cachealloc;
+	g->m->mcache->local_cachealloc = 0;
+	mstats.tinyallocs += g->m->mcache->local_tinyallocs;
+	g->m->mcache->local_tinyallocs = 0;
+
+	s = MHeap_AllocSpanLocked(h, npage);
+	if(s != nil) {
+		// Record span info, because gc needs to be
+		// able to map interior pointer to containing span.
+		runtime·atomicstore(&s->sweepgen, h->sweepgen);
+		s->state = MSpanInUse;
+		s->freelist = nil;
+		s->ref = 0;
+		s->sizeclass = sizeclass;
+		s->elemsize = (sizeclass==0 ? s->npages<<PageShift : runtime·class_to_size[sizeclass]);
+
+		// update stats, sweep lists
+		if(large) {
+			mstats.heap_objects++;
+			mstats.heap_alloc += npage<<PageShift;
+			// Swept spans are at the end of lists.
+			if(s->npages < nelem(h->free))
+				runtime·MSpanList_InsertBack(&h->busy[s->npages], s);
+			else
+				runtime·MSpanList_InsertBack(&h->busylarge, s);
+		}
+	}
+	runtime·unlock(&h->lock);
+	return s;
+}
+
+static void
+mheap_alloc_m(G *gp)
+{
+	MHeap *h;
+	MSpan *s;
+
+	h = g->m->ptrarg[0];
+	g->m->ptrarg[0] = nil;
+	s = mheap_alloc(h, g->m->scalararg[0], g->m->scalararg[1], g->m->scalararg[2]);
+	g->m->ptrarg[0] = s;
+
+	runtime·gogo(&gp->sched);
+}
+
+MSpan*
+runtime·MHeap_Alloc(MHeap *h, uintptr npage, int32 sizeclass, bool large, bool needzero)
+{
+	MSpan *s;
+	void (*fn)(G*);
+
+	// Don't do any operations that lock the heap on the G stack.
+	// It might trigger stack growth, and the stack growth code needs
+	// to be able to allocate heap.
+	if(g == g->m->g0) {
+		s = mheap_alloc(h, npage, sizeclass, large);
+	} else {
+		g->m->ptrarg[0] = h;
+		g->m->scalararg[0] = npage;
+		g->m->scalararg[1] = sizeclass;
+		g->m->scalararg[2] = large;
+		fn = mheap_alloc_m;
+		runtime·mcall(&fn);
+		s = g->m->ptrarg[0];
+		g->m->ptrarg[0] = nil;
+	}
+	if(s != nil) {
+		if(needzero && s->needzero)
+			runtime·memclr((byte*)(s->start<<PageShift), s->npages<<PageShift);
+		s->needzero = 0;
+	}
+	return s;
+}
+
+MSpan*
+runtime·MHeap_AllocStack(MHeap *h, uintptr npage)
+{
+	MSpan *s;
+
+	if(g != g->m->g0)
+		runtime·throw("mheap_allocstack not on M stack");
+	runtime·lock(&h->lock);
+	s = MHeap_AllocSpanLocked(h, npage);
+	if(s != nil) {
+		s->state = MSpanStack;
+		s->freelist = nil;
+		s->ref = 0;
+		mstats.stacks_inuse += s->npages<<PageShift;
+	}
+	runtime·unlock(&h->lock);
+	return s;
+}
+
+// Allocates a span of the given size.  h must be locked.
+// The returned span has been removed from the
+// free list, but its state is still MSpanFree.
+static MSpan*
+MHeap_AllocSpanLocked(MHeap *h, uintptr npage)
+{
+	uintptr n;
+	MSpan *s, *t;
+	pageID p;
+
+	// Try in fixed-size lists up to max.
+	for(n=npage; n < nelem(h->free); n++) {
+		if(!runtime·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)
+		runtime·throw("MHeap_AllocLocked - MSpan not free");
+	if(s->npages < npage)
+		runtime·throw("MHeap_AllocLocked - bad npages");
+	runtime·MSpanList_Remove(s);
+	if(s->next != nil || s->prev != nil)
+		runtime·throw("still in list");
+	if(s->npreleased > 0) {
+		runtime·SysUsed((void*)(s->start<<PageShift), s->npages<<PageShift);
+		mstats.heap_released -= s->npreleased<<PageShift;
+		s->npreleased = 0;
+	}
+
+	if(s->npages > npage) {
+		// Trim extra and put it back in the heap.
+		t = runtime·FixAlloc_Alloc(&h->spanalloc);
+		runtime·MSpan_Init(t, s->start + npage, s->npages - npage);
+		s->npages = npage;
+		p = t->start;
+		p -= ((uintptr)h->arena_start>>PageShift);
+		if(p > 0)
+			h->spans[p-1] = s;
+		h->spans[p] = t;
+		h->spans[p+t->npages-1] = t;
+		t->needzero = s->needzero;
+		s->state = MSpanStack; // prevent coalescing with s
+		t->state = MSpanStack;
+		MHeap_FreeSpanLocked(h, t, false, false);
+		t->unusedsince = s->unusedsince; // preserve age (TODO: wrong: t is possibly merged and/or deallocated at this point)
+		s->state = MSpanFree;
+	}
+	s->unusedsince = 0;
+
+	p = s->start;
+	p -= ((uintptr)h->arena_start>>PageShift);
+	for(n=0; n<npage; n++)
+		h->spans[p+n] = s;
+
+	mstats.heap_inuse += npage<<PageShift;
+	mstats.heap_idle -= npage<<PageShift;
+
+	//runtime·printf("spanalloc %p\n", s->start << PageShift);
+	if(s->next != nil || s->prev != nil)
+		runtime·throw("still in list");
+	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->freelarge, 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;
+	pageID p;
+
+	// 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.
+	// Allocate a multiple of 64kB.
+	npage = ROUND(npage, (64<<10)/PageSize);
+	ask = npage<<PageShift;
+	if(ask < HeapAllocChunk)
+		ask = HeapAllocChunk;
+
+	v = runtime·MHeap_SysAlloc(h, ask);
+	if(v == nil) {
+		if(ask > (npage<<PageShift)) {
+			ask = npage<<PageShift;
+			v = runtime·MHeap_SysAlloc(h, ask);
+		}
+		if(v == nil) {
+			runtime·printf("runtime: out of memory: cannot allocate %D-byte block (%D in use)\n", (uint64)ask, mstats.heap_sys);
+			return false;
+		}
+	}
+
+	// Create a fake "in use" span and free it, so that the
+	// right coalescing happens.
+	s = runtime·FixAlloc_Alloc(&h->spanalloc);
+	runtime·MSpan_Init(s, (uintptr)v>>PageShift, ask>>PageShift);
+	p = s->start;
+	p -= ((uintptr)h->arena_start>>PageShift);
+	h->spans[p] = s;
+	h->spans[p + s->npages - 1] = s;
+	runtime·atomicstore(&s->sweepgen, h->sweepgen);
+	s->state = MSpanInUse;
+	MHeap_FreeSpanLocked(h, s, false, true);
+	return true;
+}
+
+// Look up the span at the given address.
+// Address is guaranteed to be in map
+// and is guaranteed to be start or end of span.
+MSpan*
+runtime·MHeap_Lookup(MHeap *h, void *v)
+{
+	uintptr p;
+	
+	p = (uintptr)v;
+	p -= (uintptr)h->arena_start;
+	return h->spans[p >> PageShift];
+}
+
+// Look up the span at the given address.
+// Address is *not* guaranteed to be in map
+// and may be anywhere in the span.
+// Map entries for the middle of a span are only
+// valid for allocated spans.  Free spans may have
+// other garbage in their middles, so we have to
+// check for that.
+MSpan*
+runtime·MHeap_LookupMaybe(MHeap *h, void *v)
+{
+	MSpan *s;
+	pageID p, q;
+
+	if((byte*)v < h->arena_start || (byte*)v >= h->arena_used)
+		return nil;
+	p = (uintptr)v>>PageShift;
+	q = p;
+	q -= (uintptr)h->arena_start >> PageShift;
+	s = h->spans[q];
+	if(s == nil || p < s->start || v >= s->limit || s->state != MSpanInUse)
+		return nil;
+	return s;
+}
+
+// Free the span back into the heap.
+static void
+mheap_free(MHeap *h, MSpan *s, int32 acct)
+{
+	if(g != g->m->g0)
+		runtime·throw("mheap_free not on M stack");
+	runtime·lock(&h->lock);
+	mstats.heap_alloc += g->m->mcache->local_cachealloc;
+	g->m->mcache->local_cachealloc = 0;
+	mstats.tinyallocs += g->m->mcache->local_tinyallocs;
+	g->m->mcache->local_tinyallocs = 0;
+	if(acct) {
+		mstats.heap_alloc -= s->npages<<PageShift;
+		mstats.heap_objects--;
+	}
+	MHeap_FreeSpanLocked(h, s, true, true);
+	runtime·unlock(&h->lock);
+}
+
+static void
+mheap_free_m(G *gp)
+{
+	MHeap *h;
+	MSpan *s;
+	
+	h = g->m->ptrarg[0];
+	s = g->m->ptrarg[1];
+	g->m->ptrarg[0] = nil;
+	g->m->ptrarg[1] = nil;
+	mheap_free(h, s, g->m->scalararg[0]);
+	runtime·gogo(&gp->sched);
+}
+
+void
+runtime·MHeap_Free(MHeap *h, MSpan *s, int32 acct)
+{
+	void (*fn)(G*);
+
+	if(g == g->m->g0) {
+		mheap_free(h, s, acct);
+	} else {
+		g->m->ptrarg[0] = h;
+		g->m->ptrarg[1] = s;
+		g->m->scalararg[0] = acct;
+		fn = mheap_free_m;
+		runtime·mcall(&fn);
+	}
+}
+
+void
+runtime·MHeap_FreeStack(MHeap *h, MSpan *s)
+{
+	if(g != g->m->g0)
+		runtime·throw("mheap_freestack not on M stack");
+	s->needzero = 1;
+	runtime·lock(&h->lock);
+	mstats.stacks_inuse -= s->npages<<PageShift;
+	MHeap_FreeSpanLocked(h, s, true, true);
+	runtime·unlock(&h->lock);
+}
+
+static void
+MHeap_FreeSpanLocked(MHeap *h, MSpan *s, bool acctinuse, bool acctidle)
+{
+	MSpan *t;
+	pageID p;
+
+	switch(s->state) {
+	case MSpanStack:
+		if(s->ref != 0)
+			runtime·throw("MHeap_FreeSpanLocked - invalid stack free");
+		break;
+	case MSpanInUse:
+		if(s->ref != 0 || s->sweepgen != h->sweepgen) {
+			runtime·printf("MHeap_FreeSpanLocked - span %p ptr %p ref %d sweepgen %d/%d\n",
+				       s, s->start<<PageShift, s->ref, s->sweepgen, h->sweepgen);
+			runtime·throw("MHeap_FreeSpanLocked - invalid free");
+		}
+		break;
+	default:
+		runtime·throw("MHeap_FreeSpanLocked - invalid span state");
+		break;
+	}
+	if(acctinuse)
+		mstats.heap_inuse -= s->npages<<PageShift;
+	if(acctidle)
+		mstats.heap_idle += s->npages<<PageShift;
+	s->state = MSpanFree;
+	runtime·MSpanList_Remove(s);
+	// Stamp newly unused spans. The scavenger will use that
+	// info to potentially give back some pages to the OS.
+	s->unusedsince = runtime·nanotime();
+	s->npreleased = 0;
+
+	// Coalesce with earlier, later spans.
+	p = s->start;
+	p -= (uintptr)h->arena_start >> PageShift;
+	if(p > 0 && (t = h->spans[p-1]) != nil && t->state != MSpanInUse && t->state != MSpanStack) {
+		s->start = t->start;
+		s->npages += t->npages;
+		s->npreleased = t->npreleased; // absorb released pages
+		s->needzero |= t->needzero;
+		p -= t->npages;
+		h->spans[p] = s;
+		runtime·MSpanList_Remove(t);
+		t->state = MSpanDead;
+		runtime·FixAlloc_Free(&h->spanalloc, t);
+	}
+	if((p+s->npages)*sizeof(h->spans[0]) < h->spans_mapped && (t = h->spans[p+s->npages]) != nil && t->state != MSpanInUse && t->state != MSpanStack) {
+		s->npages += t->npages;
+		s->npreleased += t->npreleased;
+		s->needzero |= t->needzero;
+		h->spans[p + s->npages - 1] = s;
+		runtime·MSpanList_Remove(t);
+		t->state = MSpanDead;
+		runtime·FixAlloc_Free(&h->spanalloc, t);
+	}
+
+	// Insert s into appropriate list.
+	if(s->npages < nelem(h->free))
+		runtime·MSpanList_Insert(&h->free[s->npages], s);
+	else
+		runtime·MSpanList_Insert(&h->freelarge, s);
+}
+
+static uintptr
+scavengelist(MSpan *list, uint64 now, uint64 limit)
+{
+	uintptr released, sumreleased;
+	MSpan *s;
+
+	if(runtime·MSpanList_IsEmpty(list))
+		return 0;
+
+	sumreleased = 0;
+	for(s=list->next; s != list; s=s->next) {
+		if((now - s->unusedsince) > limit && s->npreleased != s->npages) {
+			released = (s->npages - s->npreleased) << PageShift;
+			mstats.heap_released += released;
+			sumreleased += released;
+			s->npreleased = s->npages;
+			runtime·SysUnused((void*)(s->start << PageShift), s->npages << PageShift);
+		}
+	}
+	return sumreleased;
+}
+
+void
+runtime·MHeap_Scavenge(int32 k, uint64 now, uint64 limit)
+{
+	uint32 i;
+	uintptr sumreleased;
+	MHeap *h;
+	
+	h = &runtime·mheap;
+	runtime·lock(&h->lock);
+	sumreleased = 0;
+	for(i=0; i < nelem(h->free); i++)
+		sumreleased += scavengelist(&h->free[i], now, limit);
+	sumreleased += scavengelist(&h->freelarge, now, limit);
+	runtime·unlock(&h->lock);
+
+	if(runtime·debug.gctrace > 0) {
+		if(sumreleased > 0)
+			runtime·printf("scvg%d: %D MB released\n", k, (uint64)sumreleased>>20);
+		// TODO(dvyukov): these stats are incorrect as we don't subtract stack usage from heap.
+		// But we can't call ReadMemStats on g0 holding locks.
+		runtime·printf("scvg%d: inuse: %D, idle: %D, sys: %D, released: %D, consumed: %D (MB)\n",
+			k, mstats.heap_inuse>>20, mstats.heap_idle>>20, mstats.heap_sys>>20,
+			mstats.heap_released>>20, (mstats.heap_sys - mstats.heap_released)>>20);
+	}
+}
+
+void
+runtime·scavenge_m(void)
+{
+	runtime·MHeap_Scavenge(-1, ~(uintptr)0, 0);
+}
+
+// Initialize a new span with the given start and npages.
+void
+runtime·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->incache = false;
+	span->elemsize = 0;
+	span->state = MSpanDead;
+	span->unusedsince = 0;
+	span->npreleased = 0;
+	span->specialLock.key = 0;
+	span->specials = nil;
+	span->needzero = 0;
+}
+
+// Initialize an empty doubly-linked list.
+void
+runtime·MSpanList_Init(MSpan *list)
+{
+	list->state = MSpanListHead;
+	list->next = list;
+	list->prev = list;
+}
+
+void
+runtime·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
+runtime·MSpanList_IsEmpty(MSpan *list)
+{
+	return list->next == list;
+}
+
+void
+runtime·MSpanList_Insert(MSpan *list, MSpan *span)
+{
+	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;
+}
+
+void
+runtime·MSpanList_InsertBack(MSpan *list, MSpan *span)
+{
+	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;
+	span->prev = list->prev;
+	span->next->prev = span;
+	span->prev->next = span;
+}
+
+// Adds the special record s to the list of special records for
+// the object p.  All fields of s should be filled in except for
+// offset & next, which this routine will fill in.
+// Returns true if the special was successfully added, false otherwise.
+// (The add will fail only if a record with the same p and s->kind
+//  already exists.)
+static bool
+addspecial(void *p, Special *s)
+{
+	MSpan *span;
+	Special **t, *x;
+	uintptr offset;
+	byte kind;
+
+	span = runtime·MHeap_LookupMaybe(&runtime·mheap, p);
+	if(span == nil)
+		runtime·throw("addspecial on invalid pointer");
+
+	// Ensure that the span is swept.
+	// GC accesses specials list w/o locks. And it's just much safer.
+	g->m->locks++;
+	runtime·MSpan_EnsureSwept(span);
+
+	offset = (uintptr)p - (span->start << PageShift);
+	kind = s->kind;
+
+	runtime·lock(&span->specialLock);
+
+	// Find splice point, check for existing record.
+	t = &span->specials;
+	while((x = *t) != nil) {
+		if(offset == x->offset && kind == x->kind) {
+			runtime·unlock(&span->specialLock);
+			g->m->locks--;
+			return false; // already exists
+		}
+		if(offset < x->offset || (offset == x->offset && kind < x->kind))
+			break;
+		t = &x->next;
+	}
+	// Splice in record, fill in offset.
+	s->offset = offset;
+	s->next = x;
+	*t = s;
+	runtime·unlock(&span->specialLock);
+	g->m->locks--;
+	return true;
+}
+
+// Removes the Special record of the given kind for the object p.
+// Returns the record if the record existed, nil otherwise.
+// The caller must FixAlloc_Free the result.
+static Special*
+removespecial(void *p, byte kind)
+{
+	MSpan *span;
+	Special *s, **t;
+	uintptr offset;
+
+	span = runtime·MHeap_LookupMaybe(&runtime·mheap, p);
+	if(span == nil)
+		runtime·throw("removespecial on invalid pointer");
+
+	// Ensure that the span is swept.
+	// GC accesses specials list w/o locks. And it's just much safer.
+	g->m->locks++;
+	runtime·MSpan_EnsureSwept(span);
+
+	offset = (uintptr)p - (span->start << PageShift);
+
+	runtime·lock(&span->specialLock);
+	t = &span->specials;
+	while((s = *t) != nil) {
+		// This function is used for finalizers only, so we don't check for
+		// "interior" specials (p must be exactly equal to s->offset).
+		if(offset == s->offset && kind == s->kind) {
+			*t = s->next;
+			runtime·unlock(&span->specialLock);
+			g->m->locks--;
+			return s;
+		}
+		t = &s->next;
+	}
+	runtime·unlock(&span->specialLock);
+	g->m->locks--;
+	return nil;
+}
+
+// Adds a finalizer to the object p.  Returns true if it succeeded.
+bool
+runtime·addfinalizer(void *p, FuncVal *f, uintptr nret, Type *fint, PtrType *ot)
+{
+	SpecialFinalizer *s;
+
+	runtime·lock(&runtime·mheap.speciallock);
+	s = runtime·FixAlloc_Alloc(&runtime·mheap.specialfinalizeralloc);
+	runtime·unlock(&runtime·mheap.speciallock);
+	s->special.kind = KindSpecialFinalizer;
+	s->fn = f;
+	s->nret = nret;
+	s->fint = fint;
+	s->ot = ot;
+	if(addspecial(p, &s->special))
+		return true;
+
+	// There was an old finalizer
+	runtime·lock(&runtime·mheap.speciallock);
+	runtime·FixAlloc_Free(&runtime·mheap.specialfinalizeralloc, s);
+	runtime·unlock(&runtime·mheap.speciallock);
+	return false;
+}
+
+// Removes the finalizer (if any) from the object p.
+void
+runtime·removefinalizer(void *p)
+{
+	SpecialFinalizer *s;
+
+	s = (SpecialFinalizer*)removespecial(p, KindSpecialFinalizer);
+	if(s == nil)
+		return; // there wasn't a finalizer to remove
+	runtime·lock(&runtime·mheap.speciallock);
+	runtime·FixAlloc_Free(&runtime·mheap.specialfinalizeralloc, s);
+	runtime·unlock(&runtime·mheap.speciallock);
+}
+
+// Set the heap profile bucket associated with addr to b.
+void
+runtime·setprofilebucket_m(void)
+{	
+	void *p;
+	Bucket *b;
+	SpecialProfile *s;
+	
+	p = g->m->ptrarg[0];
+	b = g->m->ptrarg[1];
+	g->m->ptrarg[0] = nil;
+	g->m->ptrarg[1] = nil;
+
+	runtime·lock(&runtime·mheap.speciallock);
+	s = runtime·FixAlloc_Alloc(&runtime·mheap.specialprofilealloc);
+	runtime·unlock(&runtime·mheap.speciallock);
+	s->special.kind = KindSpecialProfile;
+	s->b = b;
+	if(!addspecial(p, &s->special))
+		runtime·throw("setprofilebucket: profile already set");
+}
+
+// Do whatever cleanup needs to be done to deallocate s.  It has
+// already been unlinked from the MSpan specials list.
+// Returns true if we should keep working on deallocating p.
+bool
+runtime·freespecial(Special *s, void *p, uintptr size, bool freed)
+{
+	SpecialFinalizer *sf;
+	SpecialProfile *sp;
+
+	switch(s->kind) {
+	case KindSpecialFinalizer:
+		sf = (SpecialFinalizer*)s;
+		runtime·queuefinalizer(p, sf->fn, sf->nret, sf->fint, sf->ot);
+		runtime·lock(&runtime·mheap.speciallock);
+		runtime·FixAlloc_Free(&runtime·mheap.specialfinalizeralloc, sf);
+		runtime·unlock(&runtime·mheap.speciallock);
+		return false; // don't free p until finalizer is done
+	case KindSpecialProfile:
+		sp = (SpecialProfile*)s;
+		runtime·mProf_Free(sp->b, size, freed);
+		runtime·lock(&runtime·mheap.speciallock);
+		runtime·FixAlloc_Free(&runtime·mheap.specialprofilealloc, sp);
+		runtime·unlock(&runtime·mheap.speciallock);
+		return true;
+	default:
+		runtime·throw("bad special kind");
+		return true;
+	}
+}