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// 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 "arch.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*);

static void

RecordSpan(void *vh, byte *p)

{

        MHeap *h;

        MSpan *s;

        h = vh;

        s = (MSpan*)p;

        s->allnext = h->allspans;

        h->allspans = s;

}

// Initialize the heap; fetch memory using alloc.

void

runtime_MHeap_Init(MHeap *h, void *(*alloc)(uintptr))

{

        uint32 i;

        runtime_FixAlloc_Init(&h->spanalloc, sizeof(MSpan), alloc, RecordSpan, h);

        runtime_FixAlloc_Init(&h->cachealloc, sizeof(MCache), alloc, nil, nil);

        // h->mapcache needs no init

        for(i=0; i<nelem(h->free); i++)

                runtime_MSpanList_Init(&h->free[i]);

        runtime_MSpanList_Init(&h->large);

        for(i=0; i<nelem(h->central); i++)

                runtime_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*

runtime_MHeap_Alloc(MHeap *h, uintptr npage, int32 sizeclass, int32 acct)

{

        MSpan *s;

        runtime_lock(h);

        runtime_purgecachedstats(runtime_m());

        s = MHeap_AllocLocked(h, npage, sizeclass);

        if(s != nil) {

                mstats.heap_inuse += npage<<PageShift;

                if(acct) {

                        mstats.heap_objects++;

                        mstats.heap_alloc += npage<<PageShift;

                }

        }

        runtime_unlock(h);

        return s;

}

static MSpan*

MHeap_AllocLocked(MHeap *h, uintptr npage, int32 sizeclass)

{

        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);

        s->state = MSpanInUse;

        mstats.heap_idle -= s->npages<<PageShift;

        if(s->npages > npage) {

                // Trim extra and put it back in the heap.

                t = runtime_FixAlloc_Alloc(&h->spanalloc);

                mstats.mspan_inuse = h->spanalloc.inuse;

                mstats.mspan_sys = h->spanalloc.sys;

                runtime_MSpan_Init(t, s->start + npage, s->npages - npage);

                s->npages = npage;

                p = t->start;

                if(sizeof(void*) == 8)

                        p -= ((uintptr)h->arena_start>>PageShift);

                if(p > 0)

                        h->map[p-1] = s;

                h->map[p] = t;

                h->map[p+t->npages-1] = t;

                *(uintptr*)(t->start<<PageShift) = *(uintptr*)(s->start<<PageShift);  // copy "needs zeroing" mark

                t->state = MSpanInUse;

                MHeap_FreeLocked(h, t);

        }

        if(*(uintptr*)(s->start<<PageShift) != 0)

                runtime_memclr((byte*)(s->start<<PageShift), s->npages<<PageShift);

        // Record span info, because gc needs to be

        // able to map interior pointer to containing span.

        s->sizeclass = sizeclass;

        p = s->start;

        if(sizeof(void*) == 8)

                p -= ((uintptr)h->arena_start>>PageShift);

        for(n=0; n<npage; n++)

                h->map[p+n] = s;

        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;

        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 (16 pages).

        npage = (npage+15)&~15;

        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 %llu-byte block (%llu in use)\n", (unsigned long long)ask, (unsigned long long)mstats.heap_sys);

                        return false;

                }

        }

        mstats.heap_sys += ask;

        // Create a fake "in use" span and free it, so that the

        // right coalescing happens.

        s = runtime_FixAlloc_Alloc(&h->spanalloc);

        mstats.mspan_inuse = h->spanalloc.inuse;

        mstats.mspan_sys = h->spanalloc.sys;

        runtime_MSpan_Init(s, (uintptr)v>>PageShift, ask>>PageShift);

        p = s->start;

        if(sizeof(void*) == 8)

                p -= ((uintptr)h->arena_start>>PageShift);

        h->map[p] = s;

        h->map[p + s->npages - 1] = s;

        s->state = MSpanInUse;

        MHeap_FreeLocked(h, s);

        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;

        if(sizeof(void*) == 8)

                p -= (uintptr)h->arena_start;

        return h->map[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;

        if(sizeof(void*) == 8)

                q -= (uintptr)h->arena_start >> PageShift;

        s = h->map[q];

        if(s == nil || p < s->start || p - s->start >= s->npages)

                return nil;

        if(s->state != MSpanInUse)

                return nil;

        return s;

}

// Free the span back into the heap.

void

runtime_MHeap_Free(MHeap *h, MSpan *s, int32 acct)

{

        runtime_lock(h);

        runtime_purgecachedstats(runtime_m());

        mstats.heap_inuse -= s->npages<<PageShift;

        if(acct) {

                mstats.heap_alloc -= s->npages<<PageShift;

                mstats.heap_objects--;

        }

        MHeap_FreeLocked(h, s);

        runtime_unlock(h);

}

static void

MHeap_FreeLocked(MHeap *h, MSpan *s)

{

        uintptr *sp, *tp;

        MSpan *t;

        PageID p;

        if(s->state != MSpanInUse || s->ref != 0) {

                // runtime_printf("MHeap_FreeLocked - span %p ptr %p state %d ref %d\n", s, s->start<<PageShift, s->state, s->ref);

                runtime_throw("MHeap_FreeLocked - invalid free");

        }

        mstats.heap_idle += s->npages<<PageShift;

        s->state = MSpanFree;

        runtime_MSpanList_Remove(s);

        sp = (uintptr*)(s->start<<PageShift);

        // Coalesce with earlier, later spans.

        p = s->start;

        if(sizeof(void*) == 8)

                p -= (uintptr)h->arena_start >> PageShift;

        if(p > 0 && (t = h->map[p-1]) != nil && t->state != MSpanInUse) {

                tp = (uintptr*)(t->start<<PageShift);

                *tp |= *sp;     // propagate "needs zeroing" mark

                s->start = t->start;

                s->npages += t->npages;

                p -= t->npages;

                h->map[p] = s;

                runtime_MSpanList_Remove(t);

                t->state = MSpanDead;

                runtime_FixAlloc_Free(&h->spanalloc, t);

                mstats.mspan_inuse = h->spanalloc.inuse;

                mstats.mspan_sys = h->spanalloc.sys;

        }

        if(p+s->npages < nelem(h->map) && (t = h->map[p+s->npages]) != nil && t->state != MSpanInUse) {

                tp = (uintptr*)(t->start<<PageShift);

                *sp |= *tp;     // propagate "needs zeroing" mark

                s->npages += t->npages;

                h->map[p + s->npages - 1] = s;

                runtime_MSpanList_Remove(t);

                t->state = MSpanDead;

                runtime_FixAlloc_Free(&h->spanalloc, t);

                mstats.mspan_inuse = h->spanalloc.inuse;

                mstats.mspan_sys = h->spanalloc.sys;

        }

        // Insert s into appropriate list.

        if(s->npages < nelem(h->free))

                runtime_MSpanList_Insert(&h->free[s->npages], s);

        else

                runtime_MSpanList_Insert(&h->large, s);

        // TODO(rsc): IncrementalScavenge() to return memory to OS.

}

// 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->state = 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;

}