gcc/libgo/runtime/mheap.c

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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;
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.sweepspans)
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], i);
}
void
runtime_MHeap_MapSpans(MHeap *h)
{
uintptr pagesize;
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, PageSize);
pagesize = getpagesize();
n = ROUND(n, pagesize);
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);
n += runtime_MSpan_Sweep(s);
runtime_lock(h);
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);
for(;;) {
n = runtime_sweepone();
if(n == (uintptr)-1) // all spans are swept
break;
reclaimed += n;
if(reclaimed >= npage)
break;
}
runtime_lock(h);
}
// 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, bool large, bool needzero)
{
MSpan *s;
runtime_lock(h);
mstats.heap_alloc += runtime_m()->mcache->local_cachealloc;
runtime_m()->mcache->local_cachealloc = 0;
s = MHeap_AllocLocked(h, npage, sizeclass);
if(s != nil) {
mstats.heap_inuse += npage<<PageShift;
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);
if(s != nil) {
if(needzero && s->needzero)
runtime_memclr((byte*)(s->start<<PageShift), s->npages<<PageShift);
s->needzero = 0;
}
return s;
}
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
}
s->unusedsince = 0;
// Record span info, because gc needs to be
// able to map interior pointer to containing span.
s->sizeclass = sizeclass;
s->elemsize = (sizeclass==0 ? s->npages<<PageShift : (uintptr)runtime_class_to_size[sizeclass]);
s->types.compression = MTypes_Empty;
p = s->start;
p -= ((uintptr)h->arena_start>>PageShift);
for(n=0; n<npage; n++)
h->spans[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->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 (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 %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_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;
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 || (byte*)v >= s->limit || 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);
mstats.heap_alloc += runtime_m()->mcache->local_cachealloc;
runtime_m()->mcache->local_cachealloc = 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 void
MHeap_FreeLocked(MHeap *h, MSpan *s)
{
MSpan *t;
PageID p;
s->types.compression = MTypes_Empty;
if(s->state != MSpanInUse || s->ref != 0 || s->sweepgen != h->sweepgen) {
runtime_printf("MHeap_FreeLocked - span %p ptr %p state %d ref %d sweepgen %d/%d\n",
s, s->start<<PageShift, s->state, s->ref, s->sweepgen, h->sweepgen);
runtime_throw("MHeap_FreeLocked - invalid free");
}
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) {
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) {
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 void
forcegchelper(void *vnote)
{
Note *note = (Note*)vnote;
runtime_gc(1);
runtime_notewakeup(note);
}
static uintptr
scavengelist(MSpan *list, uint64 now, uint64 limit)
{
uintptr released, sumreleased, start, end, pagesize;
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;
start = s->start << PageShift;
end = start + (s->npages << PageShift);
// Round start up and end down to ensure we
// are acting on entire pages.
pagesize = getpagesize();
start = ROUND(start, pagesize);
end &= ~(pagesize - 1);
if(end > start)
runtime_SysUnused((void*)start, end - start);
}
}
return sumreleased;
}
static void
scavenge(int32 k, uint64 now, uint64 limit)
{
uint32 i;
uintptr sumreleased;
MHeap *h;
h = &runtime_mheap;
sumreleased = 0;
for(i=0; i < nelem(h->free); i++)
sumreleased += scavengelist(&h->free[i], now, limit);
sumreleased += scavengelist(&h->freelarge, now, limit);
if(runtime_debug.gctrace > 0) {
if(sumreleased > 0)
runtime_printf("scvg%d: %D MB released\n", k, (uint64)sumreleased>>20);
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);
}
}
// Release (part of) unused memory to OS.
// Goroutine created at startup.
// Loop forever.
void
runtime_MHeap_Scavenger(void* dummy)
{
G *g;
MHeap *h;
uint64 tick, now, forcegc, limit;
int64 unixnow;
uint32 k;
Note note, *notep;
USED(dummy);
g = runtime_g();
g->issystem = true;
g->isbackground = true;
// If we go two minutes without a garbage collection, force one to run.
forcegc = 2*60*1e9;
// If a span goes unused for 5 minutes after a garbage collection,
// we hand it back to the operating system.
limit = 5*60*1e9;
// Make wake-up period small enough for the sampling to be correct.
if(forcegc < limit)
tick = forcegc/2;
else
tick = limit/2;
h = &runtime_mheap;
for(k=0;; k++) {
runtime_noteclear(&note);
runtime_notetsleepg(&note, tick);
runtime_lock(h);
unixnow = runtime_unixnanotime();
if(unixnow - mstats.last_gc > forcegc) {
runtime_unlock(h);
// The scavenger can not block other goroutines,
// otherwise deadlock detector can fire spuriously.
// GC blocks other goroutines via the runtime_worldsema.
runtime_noteclear(&note);
notep = &note;
__go_go(forcegchelper, (void*)notep);
runtime_notetsleepg(&note, -1);
if(runtime_debug.gctrace > 0)
runtime_printf("scvg%d: GC forced\n", k);
runtime_lock(h);
}
now = runtime_nanotime();
scavenge(k, now, limit);
runtime_unlock(h);
}
}
void runtime_debug_freeOSMemory(void) __asm__("runtime_debug.freeOSMemory");
void
runtime_debug_freeOSMemory(void)
{
runtime_gc(2); // force GC and do eager sweep
runtime_lock(&runtime_mheap);
scavenge(-1, ~(uintptr)0, 0);
runtime_unlock(&runtime_mheap);
}
// 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->types.compression = MTypes_Empty;
span->specialLock.key = 0;
span->specials = nil;
span->needzero = 0;
span->freebuf = nil;
}
// 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.
runtime_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);
runtime_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);
runtime_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.
runtime_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);
runtime_m()->locks--;
return s;
}
t = &s->next;
}
runtime_unlock(&span->specialLock);
runtime_m()->locks--;
return nil;
}
// Adds a finalizer to the object p. Returns true if it succeeded.
bool
runtime_addfinalizer(void *p, FuncVal *f, const FuncType *ft, const PtrType *ot)
{
SpecialFinalizer *s;
runtime_lock(&runtime_mheap.speciallock);
s = runtime_FixAlloc_Alloc(&runtime_mheap.specialfinalizeralloc);
runtime_unlock(&runtime_mheap.speciallock);
s->kind = KindSpecialFinalizer;
s->fn = f;
s->ft = ft;
s->ot = ot;
if(addspecial(p, s))
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(void *p, Bucket *b)
{
SpecialProfile *s;
runtime_lock(&runtime_mheap.speciallock);
s = runtime_FixAlloc_Alloc(&runtime_mheap.specialprofilealloc);
runtime_unlock(&runtime_mheap.speciallock);
s->kind = KindSpecialProfile;
s->b = b;
if(!addspecial(p, s))
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->ft, 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;
}
}
// Free all special records for p.
void
runtime_freeallspecials(MSpan *span, void *p, uintptr size)
{
Special *s, **t, *list;
uintptr offset;
if(span->sweepgen != runtime_mheap.sweepgen)
runtime_throw("runtime: freeallspecials: unswept span");
// first, collect all specials into the list; then, free them
// this is required to not cause deadlock between span->specialLock and proflock
list = nil;
offset = (uintptr)p - (span->start << PageShift);
runtime_lock(&span->specialLock);
t = &span->specials;
while((s = *t) != nil) {
if(offset + size <= s->offset)
break;
if(offset <= s->offset) {
*t = s->next;
s->next = list;
list = s;
} else
t = &s->next;
}
runtime_unlock(&span->specialLock);
while(list != nil) {
s = list;
list = s->next;
if(!runtime_freespecial(s, p, size, true))
runtime_throw("can't explicitly free an object with a finalizer");
}
}
// Split an allocated span into two equal parts.
void
runtime_MHeap_SplitSpan(MHeap *h, MSpan *s)
{
MSpan *t;
MCentral *c;
uintptr i;
uintptr npages;
PageID p;
if(s->state != MSpanInUse)
runtime_throw("MHeap_SplitSpan on a free span");
if(s->sizeclass != 0 && s->ref != 1)
runtime_throw("MHeap_SplitSpan doesn't have an allocated object");
npages = s->npages;
// remove the span from whatever list it is in now
if(s->sizeclass > 0) {
// must be in h->central[x].empty
c = &h->central[s->sizeclass];
runtime_lock(c);
runtime_MSpanList_Remove(s);
runtime_unlock(c);
runtime_lock(h);
} else {
// must be in h->busy/busylarge
runtime_lock(h);
runtime_MSpanList_Remove(s);
}
// heap is locked now
if(npages == 1) {
// convert span of 1 PageSize object to a span of 2 PageSize/2 objects.
s->ref = 2;
s->sizeclass = runtime_SizeToClass(PageSize/2);
s->elemsize = PageSize/2;
} else {
// convert span of n>1 pages into two spans of n/2 pages each.
if((s->npages & 1) != 0)
runtime_throw("MHeap_SplitSpan on an odd size span");
// compute position in h->spans
p = s->start;
p -= (uintptr)h->arena_start >> PageShift;
// Allocate a new span for the first half.
t = runtime_FixAlloc_Alloc(&h->spanalloc);
runtime_MSpan_Init(t, s->start, npages/2);
t->limit = (byte*)((t->start + npages/2) << PageShift);
t->state = MSpanInUse;
t->elemsize = npages << (PageShift - 1);
t->sweepgen = s->sweepgen;
if(t->elemsize <= MaxSmallSize) {
t->sizeclass = runtime_SizeToClass(t->elemsize);
t->ref = 1;
}
// the old span holds the second half.
s->start += npages/2;
s->npages = npages/2;
s->elemsize = npages << (PageShift - 1);
if(s->elemsize <= MaxSmallSize) {
s->sizeclass = runtime_SizeToClass(s->elemsize);
s->ref = 1;
}
// update span lookup table
for(i = p; i < p + npages/2; i++)
h->spans[i] = t;
}
// place the span into a new list
if(s->sizeclass > 0) {
runtime_unlock(h);
c = &h->central[s->sizeclass];
runtime_lock(c);
// swept spans are at the end of the list
runtime_MSpanList_InsertBack(&c->empty, s);
runtime_unlock(c);
} else {
// 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);
}
}