static MSpan*
MHeap_AllocLocked(MHeap *h, uintptr npage, int32 sizeclass)
{
uintptr n;
MSpan *s, *t;
PageID p;
// 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);
// 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);
runtime_atomicstore(&s->sweepgen, h->sweepgen);
s->state = MSpanInUse;
mstats.heap_idle -= s->npages<<PageShift;
mstats.heap_released -= s->npreleased<<PageShift;
if(s->npreleased > 0)
runtime_SysUsed((void*)(s->start<<PageShift), s->npages<<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;
runtime_atomicstore(&t->sweepgen, h->sweepgen);
t->state = MSpanInUse;
MHeap_FreeLocked(h, t);
t->unusedsince = s->unusedsince; // preserve age
}
// Free the span back into the heap.
void
MHeap_Free(MHeap *h, MSpan *s, int32 acct)
{
lock(h);
mstats.heap_alloc += m->mcache->local_alloc;
m->mcache->local_alloc = 0;
mstats.heap_inuse -= s->npages<<PageShift;
if(acct)
mstats.heap_alloc -= s->npages<<PageShift;
MHeap_FreeLocked(h, s);
unlock(h);
}
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;
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);
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);
}
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);
mstats.mspan_inuse = h->spanalloc.inuse;
mstats.mspan_sys = h->spanalloc.sys;
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);
}
// Record 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);
return s;
}
// 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.
// For Native Client, allocate a multiple of 64kB (16 pages).
npage = (npage+15)&~15;
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;
}
mstats.heap_sys += ask;
if((byte*)v < h->min || h->min == nil)
h->min = v;
if((byte*)v+ask > h->max)
h->max = (byte*)v+ask;
// 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;
}
// Create a fake "in use" span and free it, so that the
// right coalescing happens.
s = FixAlloc_Alloc(&h->spanalloc);
mstats.mspan_inuse = h->spanalloc.inuse;
mstats.mspan_sys = h->spanalloc.sys;
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;
}
// Free the span back into the heap.
void
runtime·MHeap_Free(MHeap *h, MSpan *s, int32 acct)
{
runtime·lock(h);
mstats.heap_alloc += m->mcache->local_alloc;
m->mcache->local_alloc = 0;
mstats.heap_objects += m->mcache->local_objects;
m->mcache->local_objects = 0;
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 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;
mstats.heap_released -= s->npreleased<<PageShift;
if(s->npreleased > 0) {
// We have called runtime·SysUnused with these pages, and on
// Unix systems it called madvise. At this point at least
// some BSD-based kernels will return these pages either as
// zeros or with the old data. For our caller, the first word
// in the page indicates whether the span contains zeros or
// not (this word was set when the span was freed by
// MCentral_Free or runtime·MCentral_FreeSpan). If the first
// page in the span is returned as zeros, and some subsequent
// page is returned with the old data, then we will be
// returning a span that is assumed to be all zeros, but the
// actual data will not be all zeros. Avoid that problem by
// explicitly marking the span as not being zeroed, just in
// case. The beadbead constant we use here means nothing, it
// is just a unique constant not seen elsewhere in the
// runtime, as a clue in case it turns up unexpectedly in
// memory or in a stack trace.
*(uintptr*)(s->start<<PageShift) = (uintptr)0xbeadbeadbeadbeadULL;
}
s->npreleased = 0;
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);
t->unusedsince = s->unusedsince; // preserve age
}