Retro68/gcc/libgo/runtime/mheap.c
2014-09-21 19:33:12 +02:00

565 lines
15 KiB
C

// 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]));
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);
// 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);
}
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, &mstats.other_sys);
h->spans_mapped = n;
}
// 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, int32 zeroed)
{
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(acct) {
mstats.heap_objects++;
mstats.heap_alloc += npage<<PageShift;
}
}
runtime_unlock(h);
if(s != nil && *(uintptr*)(s->start<<PageShift) != 0 && zeroed)
runtime_memclr((byte*)(s->start<<PageShift), s->npages<<PageShift);
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;
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.
runtime_SysUsed((void*)(s->start<<PageShift), s->npages<<PageShift);
*(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);
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;
*(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
}
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->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 %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;
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)
{
uintptr *sp, *tp;
MSpan *t;
PageID p;
s->types.compression = MTypes_Empty;
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);
// 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) {
if(t->npreleased == 0) { // cant't touch this otherwise
tp = (uintptr*)(t->start<<PageShift);
*tp |= *sp; // propagate "needs zeroing" mark
}
s->start = t->start;
s->npages += t->npages;
s->npreleased = t->npreleased; // absorb released pages
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) {
if(t->npreleased == 0) { // cant't touch this otherwise
tp = (uintptr*)(t->start<<PageShift);
*sp |= *tp; // propagate "needs zeroing" mark
}
s->npages += t->npages;
s->npreleased += t->npreleased;
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->large, 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->large, 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;
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);
now = runtime_nanotime();
if(now - 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(1);
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->elemsize = 0;
span->state = 0;
span->unusedsince = 0;
span->npreleased = 0;
span->types.compression = MTypes_Empty;
}
// 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;
}