2010-12-03 05:34:57 +01:00
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// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Page heap.
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//
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// See malloc.h for overview.
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//
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// When a MSpan is in the heap free list, state == MSpanFree
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// and heapmap(s->start) == span, heapmap(s->start+s->npages-1) == span.
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//
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// When a MSpan is allocated, state == MSpanInUse
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// and heapmap(i) == span for all s->start <= i < s->start+s->npages.
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#include "runtime.h"
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#include "malloc.h"
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static MSpan *MHeap_AllocLocked(MHeap*, uintptr, int32);
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static bool MHeap_Grow(MHeap*, uintptr);
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static void MHeap_FreeLocked(MHeap*, MSpan*);
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static MSpan *MHeap_AllocLarge(MHeap*, uintptr);
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static MSpan *BestFit(MSpan*, uintptr, MSpan*);
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static void
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RecordSpan(void *vh, byte *p)
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{
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MHeap *h;
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MSpan *s;
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h = vh;
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s = (MSpan*)p;
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s->allnext = h->allspans;
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h->allspans = s;
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}
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// Initialize the heap; fetch memory using alloc.
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void
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runtime_MHeap_Init(MHeap *h, void *(*alloc)(uintptr))
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{
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uint32 i;
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runtime_initlock(h);
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runtime_FixAlloc_Init(&h->spanalloc, sizeof(MSpan), alloc, RecordSpan, h);
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runtime_FixAlloc_Init(&h->cachealloc, sizeof(MCache), alloc, nil, nil);
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runtime_MHeapMap_Init(&h->map, alloc);
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// h->mapcache needs no init
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for(i=0; i<nelem(h->free); i++)
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runtime_MSpanList_Init(&h->free[i]);
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runtime_MSpanList_Init(&h->large);
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for(i=0; i<nelem(h->central); i++)
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runtime_MCentral_Init(&h->central[i], i);
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}
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// Allocate a new span of npage pages from the heap
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// and record its size class in the HeapMap and HeapMapCache.
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MSpan*
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runtime_MHeap_Alloc(MHeap *h, uintptr npage, int32 sizeclass, int32 acct)
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{
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MSpan *s;
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runtime_lock(h);
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mstats.heap_alloc += m->mcache->local_alloc;
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m->mcache->local_alloc = 0;
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mstats.heap_objects += m->mcache->local_objects;
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m->mcache->local_objects = 0;
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s = MHeap_AllocLocked(h, npage, sizeclass);
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if(s != nil) {
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mstats.heap_inuse += npage<<PageShift;
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if(acct) {
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mstats.heap_objects++;
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mstats.heap_alloc += npage<<PageShift;
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}
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}
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runtime_unlock(h);
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return s;
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}
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static MSpan*
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MHeap_AllocLocked(MHeap *h, uintptr npage, int32 sizeclass)
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{
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uintptr n;
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MSpan *s, *t;
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// Try in fixed-size lists up to max.
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for(n=npage; n < nelem(h->free); n++) {
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if(!runtime_MSpanList_IsEmpty(&h->free[n])) {
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s = h->free[n].next;
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goto HaveSpan;
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}
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}
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// Best fit in list of large spans.
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if((s = MHeap_AllocLarge(h, npage)) == nil) {
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if(!MHeap_Grow(h, npage))
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return nil;
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if((s = MHeap_AllocLarge(h, npage)) == nil)
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return nil;
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}
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HaveSpan:
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// Mark span in use.
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if(s->state != MSpanFree)
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runtime_throw("MHeap_AllocLocked - MSpan not free");
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if(s->npages < npage)
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runtime_throw("MHeap_AllocLocked - bad npages");
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runtime_MSpanList_Remove(s);
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s->state = MSpanInUse;
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if(s->npages > npage) {
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// Trim extra and put it back in the heap.
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t = runtime_FixAlloc_Alloc(&h->spanalloc);
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mstats.mspan_inuse = h->spanalloc.inuse;
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mstats.mspan_sys = h->spanalloc.sys;
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runtime_MSpan_Init(t, s->start + npage, s->npages - npage);
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s->npages = npage;
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runtime_MHeapMap_Set(&h->map, t->start - 1, s);
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runtime_MHeapMap_Set(&h->map, t->start, t);
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runtime_MHeapMap_Set(&h->map, t->start + t->npages - 1, t);
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t->state = MSpanInUse;
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MHeap_FreeLocked(h, t);
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}
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// Record span info, because gc needs to be
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// able to map interior pointer to containing span.
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s->sizeclass = sizeclass;
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for(n=0; n<npage; n++)
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runtime_MHeapMap_Set(&h->map, s->start+n, s);
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return s;
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}
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// Allocate a span of exactly npage pages from the list of large spans.
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static MSpan*
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MHeap_AllocLarge(MHeap *h, uintptr npage)
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{
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return BestFit(&h->large, npage, nil);
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}
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// Search list for smallest span with >= npage pages.
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// If there are multiple smallest spans, take the one
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// with the earliest starting address.
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static MSpan*
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BestFit(MSpan *list, uintptr npage, MSpan *best)
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{
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MSpan *s;
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for(s=list->next; s != list; s=s->next) {
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if(s->npages < npage)
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continue;
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if(best == nil
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|| s->npages < best->npages
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|| (s->npages == best->npages && s->start < best->start))
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best = s;
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}
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return best;
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}
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// Try to add at least npage pages of memory to the heap,
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// returning whether it worked.
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static bool
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MHeap_Grow(MHeap *h, uintptr npage)
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{
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uintptr ask;
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void *v;
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MSpan *s;
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// Ask for a big chunk, to reduce the number of mappings
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// the operating system needs to track; also amortizes
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// the overhead of an operating system mapping.
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2011-01-21 19:19:03 +01:00
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// Allocate a multiple of 64kB (16 pages).
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2010-12-03 05:34:57 +01:00
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npage = (npage+15)&~15;
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ask = npage<<PageShift;
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if(ask < HeapAllocChunk)
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ask = HeapAllocChunk;
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v = runtime_SysAlloc(ask);
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if(v == nil) {
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if(ask > (npage<<PageShift)) {
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ask = npage<<PageShift;
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v = runtime_SysAlloc(ask);
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}
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if(v == nil)
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return false;
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}
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mstats.heap_sys += ask;
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if((byte*)v < h->min || h->min == nil)
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h->min = v;
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if((byte*)v+ask > h->max)
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h->max = (byte*)v+ask;
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// NOTE(rsc): In tcmalloc, if we've accumulated enough
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// system allocations, the heap map gets entirely allocated
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// in 32-bit mode. (In 64-bit mode that's not practical.)
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if(!runtime_MHeapMap_Preallocate(&h->map, ((uintptr)v>>PageShift) - 1, (ask>>PageShift) + 2)) {
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runtime_SysFree(v, ask);
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return false;
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}
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// Create a fake "in use" span and free it, so that the
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// right coalescing happens.
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s = runtime_FixAlloc_Alloc(&h->spanalloc);
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mstats.mspan_inuse = h->spanalloc.inuse;
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mstats.mspan_sys = h->spanalloc.sys;
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runtime_MSpan_Init(s, (uintptr)v>>PageShift, ask>>PageShift);
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runtime_MHeapMap_Set(&h->map, s->start, s);
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runtime_MHeapMap_Set(&h->map, s->start + s->npages - 1, s);
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s->state = MSpanInUse;
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MHeap_FreeLocked(h, s);
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return true;
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}
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// Look up the span at the given page number.
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// Page number is guaranteed to be in map
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// and is guaranteed to be start or end of span.
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MSpan*
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runtime_MHeap_Lookup(MHeap *h, PageID p)
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{
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return runtime_MHeapMap_Get(&h->map, p);
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}
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// Look up the span at the given page number.
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// Page number is *not* guaranteed to be in map
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// and may be anywhere in the span.
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// Map entries for the middle of a span are only
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// valid for allocated spans. Free spans may have
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// other garbage in their middles, so we have to
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// check for that.
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MSpan*
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runtime_MHeap_LookupMaybe(MHeap *h, PageID p)
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{
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MSpan *s;
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s = runtime_MHeapMap_GetMaybe(&h->map, p);
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if(s == nil || p < s->start || p - s->start >= s->npages)
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return nil;
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if(s->state != MSpanInUse)
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return nil;
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return s;
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}
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// Free the span back into the heap.
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void
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runtime_MHeap_Free(MHeap *h, MSpan *s, int32 acct)
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{
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runtime_lock(h);
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mstats.heap_alloc += m->mcache->local_alloc;
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m->mcache->local_alloc = 0;
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mstats.heap_objects += m->mcache->local_objects;
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m->mcache->local_objects = 0;
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mstats.heap_inuse -= s->npages<<PageShift;
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if(acct) {
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mstats.heap_alloc -= s->npages<<PageShift;
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mstats.heap_objects--;
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}
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MHeap_FreeLocked(h, s);
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runtime_unlock(h);
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}
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static void
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MHeap_FreeLocked(MHeap *h, MSpan *s)
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{
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MSpan *t;
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if(s->state != MSpanInUse || s->ref != 0) {
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// runtime_printf("MHeap_FreeLocked - span %p ptr %p state %d ref %d\n", s, s->start<<PageShift, s->state, s->ref);
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runtime_throw("MHeap_FreeLocked - invalid free");
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}
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s->state = MSpanFree;
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runtime_MSpanList_Remove(s);
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// Coalesce with earlier, later spans.
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if((t = runtime_MHeapMap_Get(&h->map, s->start - 1)) != nil && t->state != MSpanInUse) {
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s->start = t->start;
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s->npages += t->npages;
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runtime_MHeapMap_Set(&h->map, s->start, s);
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runtime_MSpanList_Remove(t);
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t->state = MSpanDead;
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runtime_FixAlloc_Free(&h->spanalloc, t);
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mstats.mspan_inuse = h->spanalloc.inuse;
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mstats.mspan_sys = h->spanalloc.sys;
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}
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if((t = runtime_MHeapMap_Get(&h->map, s->start + s->npages)) != nil && t->state != MSpanInUse) {
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s->npages += t->npages;
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runtime_MHeapMap_Set(&h->map, s->start + s->npages - 1, s);
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runtime_MSpanList_Remove(t);
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t->state = MSpanDead;
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runtime_FixAlloc_Free(&h->spanalloc, t);
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mstats.mspan_inuse = h->spanalloc.inuse;
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mstats.mspan_sys = h->spanalloc.sys;
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}
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// Insert s into appropriate list.
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if(s->npages < nelem(h->free))
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runtime_MSpanList_Insert(&h->free[s->npages], s);
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else
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runtime_MSpanList_Insert(&h->large, s);
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// TODO(rsc): IncrementalScavenge() to return memory to OS.
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}
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// Initialize a new span with the given start and npages.
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void
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runtime_MSpan_Init(MSpan *span, PageID start, uintptr npages)
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{
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span->next = nil;
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span->prev = nil;
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span->start = start;
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span->npages = npages;
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span->freelist = nil;
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span->ref = 0;
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span->sizeclass = 0;
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span->state = 0;
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}
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// Initialize an empty doubly-linked list.
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void
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runtime_MSpanList_Init(MSpan *list)
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{
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list->state = MSpanListHead;
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list->next = list;
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list->prev = list;
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}
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void
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runtime_MSpanList_Remove(MSpan *span)
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{
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if(span->prev == nil && span->next == nil)
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return;
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span->prev->next = span->next;
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span->next->prev = span->prev;
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span->prev = nil;
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span->next = nil;
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}
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bool
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runtime_MSpanList_IsEmpty(MSpan *list)
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{
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return list->next == list;
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}
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void
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runtime_MSpanList_Insert(MSpan *list, MSpan *span)
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{
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if(span->next != nil || span->prev != nil)
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runtime_throw("MSpanList_Insert");
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span->next = list->next;
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span->prev = list;
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span->next->prev = span;
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span->prev->next = span;
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}
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