[AArch64 costs 7/18] Improve SET cost.

[official-gcc.git] / libgo / runtime / mheap.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;
}