libgo/runtime/mheap.c

   1 // Copyright 2009 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 // Page heap.
   6 //
   7 // See malloc.h for overview.
   8 //
   9 // When a MSpan is in the heap free list, state == MSpanFree
  10 // and heapmap(s->start) == span, heapmap(s->start+s->npages-1) == span.
  11 //
  12 // When a MSpan is allocated, state == MSpanInUse
  13 // and heapmap(i) == span for all s->start <= i < s->start+s->npages.
  14
  15 #include "runtime.h"
  16 #include "arch.h"
  17 #include "malloc.h"
  18
  19 static MSpan *MHeap_AllocLocked(MHeap*, uintptr, int32);
  20 static bool MHeap_Grow(MHeap*, uintptr);
  21 static void MHeap_FreeLocked(MHeap*, MSpan*);
  22 static MSpan *MHeap_AllocLarge(MHeap*, uintptr);
  23 static MSpan *BestFit(MSpan*, uintptr, MSpan*);
  24
  25 static void
  26 RecordSpan(void *vh, byte *p)
  27 {
  28         MHeap *h;
  29         MSpan *s;
  30
  31         h = vh;
  32         s = (MSpan*)p;
  33         s->allnext = h->allspans;
  34         h->allspans = s;
  35 }
  36
  37 // Initialize the heap; fetch memory using alloc.
  38 void
  39 runtime_MHeap_Init(MHeap *h, void *(*alloc)(uintptr))
  40 {
  41         uint32 i;
  42
  43         runtime_FixAlloc_Init(&h->spanalloc, sizeof(MSpan), alloc, RecordSpan, h);
  44         runtime_FixAlloc_Init(&h->cachealloc, sizeof(MCache), alloc, nil, nil);
  45         // h->mapcache needs no init
  46         for(i=0; i<nelem(h->free); i++)
  47                 runtime_MSpanList_Init(&h->free[i]);
  48         runtime_MSpanList_Init(&h->large);
  49         for(i=0; i<nelem(h->central); i++)
  50                 runtime_MCentral_Init(&h->central[i], i);
  51 }
  52
  53 // Allocate a new span of npage pages from the heap
  54 // and record its size class in the HeapMap and HeapMapCache.
  55 MSpan*
  56 runtime_MHeap_Alloc(MHeap *h, uintptr npage, int32 sizeclass, int32 acct)
  57 {
  58         MSpan *s;
  59
  60         runtime_lock(h);
  61         runtime_purgecachedstats(runtime_m());
  62         s = MHeap_AllocLocked(h, npage, sizeclass);
  63         if(s != nil) {
  64                 mstats.heap_inuse += npage<<PageShift;
  65                 if(acct) {
  66                         mstats.heap_objects++;
  67                         mstats.heap_alloc += npage<<PageShift;
  68                 }
  69         }
  70         runtime_unlock(h);
  71         return s;
  72 }
  73
  74 static MSpan*
  75 MHeap_AllocLocked(MHeap *h, uintptr npage, int32 sizeclass)
  76 {
  77         uintptr n;
  78         MSpan *s, *t;
  79         PageID p;
  80
  81         // Try in fixed-size lists up to max.
  82         for(n=npage; n < nelem(h->free); n++) {
  83                 if(!runtime_MSpanList_IsEmpty(&h->free[n])) {
  84                         s = h->free[n].next;
  85                         goto HaveSpan;
  86                 }
  87         }
  88
  89         // Best fit in list of large spans.
  90         if((s = MHeap_AllocLarge(h, npage)) == nil) {
  91                 if(!MHeap_Grow(h, npage))
  92                         return nil;
  93                 if((s = MHeap_AllocLarge(h, npage)) == nil)
  94                         return nil;
  95         }
  96
  97 HaveSpan:
  98         // Mark span in use.
  99         if(s->state != MSpanFree)
 100                 runtime_throw("MHeap_AllocLocked - MSpan not free");
 101         if(s->npages < npage)
 102                 runtime_throw("MHeap_AllocLocked - bad npages");
 103         runtime_MSpanList_Remove(s);
 104         s->state = MSpanInUse;
 105         mstats.heap_idle -= s->npages<<PageShift;
 106
 107         if(s->npages > npage) {
 108                 // Trim extra and put it back in the heap.
 109                 t = runtime_FixAlloc_Alloc(&h->spanalloc);
 110                 mstats.mspan_inuse = h->spanalloc.inuse;
 111                 mstats.mspan_sys = h->spanalloc.sys;
 112                 runtime_MSpan_Init(t, s->start + npage, s->npages - npage);
 113                 s->npages = npage;
 114                 p = t->start;
 115                 if(sizeof(void*) == 8)
 116                         p -= ((uintptr)h->arena_start>>PageShift);
 117                 if(p > 0)
 118                         h->map[p-1] = s;
 119                 h->map[p] = t;
 120                 h->map[p+t->npages-1] = t;
 121                 *(uintptr*)(t->start<<PageShift) = *(uintptr*)(s->start<<PageShift);  // copy "needs zeroing" mark
 122                 t->state = MSpanInUse;
 123                 MHeap_FreeLocked(h, t);
 124         }
 125
 126         if(*(uintptr*)(s->start<<PageShift) != 0)
 127                 runtime_memclr((byte*)(s->start<<PageShift), s->npages<<PageShift);
 128
 129         // Record span info, because gc needs to be
 130         // able to map interior pointer to containing span.
 131         s->sizeclass = sizeclass;
 132         p = s->start;
 133         if(sizeof(void*) == 8)
 134                 p -= ((uintptr)h->arena_start>>PageShift);
 135         for(n=0; n<npage; n++)
 136                 h->map[p+n] = s;
 137         return s;
 138 }
 139
 140 // Allocate a span of exactly npage pages from the list of large spans.
 141 static MSpan*
 142 MHeap_AllocLarge(MHeap *h, uintptr npage)
 143 {
 144         return BestFit(&h->large, npage, nil);
 145 }
 146
 147 // Search list for smallest span with >= npage pages.
 148 // If there are multiple smallest spans, take the one
 149 // with the earliest starting address.
 150 static MSpan*
 151 BestFit(MSpan *list, uintptr npage, MSpan *best)
 152 {
 153         MSpan *s;
 154
 155         for(s=list->next; s != list; s=s->next) {
 156                 if(s->npages < npage)
 157                         continue;
 158                 if(best == nil
 159                 || s->npages < best->npages
 160                 || (s->npages == best->npages && s->start < best->start))
 161                         best = s;
 162         }
 163         return best;
 164 }
 165
 166 // Try to add at least npage pages of memory to the heap,
 167 // returning whether it worked.
 168 static bool
 169 MHeap_Grow(MHeap *h, uintptr npage)
 170 {
 171         uintptr ask;
 172         void *v;
 173         MSpan *s;
 174         PageID p;
 175
 176         // Ask for a big chunk, to reduce the number of mappings
 177         // the operating system needs to track; also amortizes
 178         // the overhead of an operating system mapping.
 179         // Allocate a multiple of 64kB (16 pages).
 180         npage = (npage+15)&~15;
 181         ask = npage<<PageShift;
 182         if(ask < HeapAllocChunk)
 183                 ask = HeapAllocChunk;
 184
 185         v = runtime_MHeap_SysAlloc(h, ask);
 186         if(v == nil) {
 187                 if(ask > (npage<<PageShift)) {
 188                         ask = npage<<PageShift;
 189                         v = runtime_MHeap_SysAlloc(h, ask);
 190                 }
 191                 if(v == nil) {
 192                         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);
 193                         return false;
 194                 }
 195         }
 196         mstats.heap_sys += ask;
 197
 198         // Create a fake "in use" span and free it, so that the
 199         // right coalescing happens.
 200         s = runtime_FixAlloc_Alloc(&h->spanalloc);
 201         mstats.mspan_inuse = h->spanalloc.inuse;
 202         mstats.mspan_sys = h->spanalloc.sys;
 203         runtime_MSpan_Init(s, (uintptr)v>>PageShift, ask>>PageShift);
 204         p = s->start;
 205         if(sizeof(void*) == 8)
 206                 p -= ((uintptr)h->arena_start>>PageShift);
 207         h->map[p] = s;
 208         h->map[p + s->npages - 1] = s;
 209         s->state = MSpanInUse;
 210         MHeap_FreeLocked(h, s);
 211         return true;
 212 }
 213
 214 // Look up the span at the given address.
 215 // Address is guaranteed to be in map
 216 // and is guaranteed to be start or end of span.
 217 MSpan*
 218 runtime_MHeap_Lookup(MHeap *h, void *v)
 219 {
 220         uintptr p;
 221
 222         p = (uintptr)v;
 223         if(sizeof(void*) == 8)
 224                 p -= (uintptr)h->arena_start;
 225         return h->map[p >> PageShift];
 226 }
 227
 228 // Look up the span at the given address.
 229 // Address is *not* guaranteed to be in map
 230 // and may be anywhere in the span.
 231 // Map entries for the middle of a span are only
 232 // valid for allocated spans.  Free spans may have
 233 // other garbage in their middles, so we have to
 234 // check for that.
 235 MSpan*
 236 runtime_MHeap_LookupMaybe(MHeap *h, void *v)
 237 {
 238         MSpan *s;
 239         PageID p, q;
 240
 241         if((byte*)v < h->arena_start || (byte*)v >= h->arena_used)
 242                 return nil;
 243         p = (uintptr)v>>PageShift;
 244         q = p;
 245         if(sizeof(void*) == 8)
 246                 q -= (uintptr)h->arena_start >> PageShift;
 247         s = h->map[q];
 248         if(s == nil || p < s->start || p - s->start >= s->npages)
 249                 return nil;
 250         if(s->state != MSpanInUse)
 251                 return nil;
 252         return s;
 253 }
 254
 255 // Free the span back into the heap.
 256 void
 257 runtime_MHeap_Free(MHeap *h, MSpan *s, int32 acct)
 258 {
 259         runtime_lock(h);
 260         runtime_purgecachedstats(runtime_m());
 261         mstats.heap_inuse -= s->npages<<PageShift;
 262         if(acct) {
 263                 mstats.heap_alloc -= s->npages<<PageShift;
 264                 mstats.heap_objects--;
 265         }
 266         MHeap_FreeLocked(h, s);
 267         runtime_unlock(h);
 268 }
 269
 270 static void
 271 MHeap_FreeLocked(MHeap *h, MSpan *s)
 272 {
 273         uintptr *sp, *tp;
 274         MSpan *t;
 275         PageID p;
 276
 277         if(s->state != MSpanInUse || s->ref != 0) {
 278                 // runtime_printf("MHeap_FreeLocked - span %p ptr %p state %d ref %d\n", s, s->start<<PageShift, s->state, s->ref);
 279                 runtime_throw("MHeap_FreeLocked - invalid free");
 280         }
 281         mstats.heap_idle += s->npages<<PageShift;
 282         s->state = MSpanFree;
 283         runtime_MSpanList_Remove(s);
 284         sp = (uintptr*)(s->start<<PageShift);
 285
 286         // Coalesce with earlier, later spans.
 287         p = s->start;
 288         if(sizeof(void*) == 8)
 289                 p -= (uintptr)h->arena_start >> PageShift;
 290         if(p > 0 && (t = h->map[p-1]) != nil && t->state != MSpanInUse) {
 291                 tp = (uintptr*)(t->start<<PageShift);
 292                 *tp |= *sp;     // propagate "needs zeroing" mark
 293                 s->start = t->start;
 294                 s->npages += t->npages;
 295                 p -= t->npages;
 296                 h->map[p] = s;
 297                 runtime_MSpanList_Remove(t);
 298                 t->state = MSpanDead;
 299                 runtime_FixAlloc_Free(&h->spanalloc, t);
 300                 mstats.mspan_inuse = h->spanalloc.inuse;
 301                 mstats.mspan_sys = h->spanalloc.sys;
 302         }
 303         if(p+s->npages < nelem(h->map) && (t = h->map[p+s->npages]) != nil && t->state != MSpanInUse) {
 304                 tp = (uintptr*)(t->start<<PageShift);
 305                 *sp |= *tp;     // propagate "needs zeroing" mark
 306                 s->npages += t->npages;
 307                 h->map[p + s->npages - 1] = s;
 308                 runtime_MSpanList_Remove(t);
 309                 t->state = MSpanDead;
 310                 runtime_FixAlloc_Free(&h->spanalloc, t);
 311                 mstats.mspan_inuse = h->spanalloc.inuse;
 312                 mstats.mspan_sys = h->spanalloc.sys;
 313         }
 314
 315         // Insert s into appropriate list.
 316         if(s->npages < nelem(h->free))
 317                 runtime_MSpanList_Insert(&h->free[s->npages], s);
 318         else
 319                 runtime_MSpanList_Insert(&h->large, s);
 320
 321         // TODO(rsc): IncrementalScavenge() to return memory to OS.
 322 }
 323
 324 // Initialize a new span with the given start and npages.
 325 void
 326 runtime_MSpan_Init(MSpan *span, PageID start, uintptr npages)
 327 {
 328         span->next = nil;
 329         span->prev = nil;
 330         span->start = start;
 331         span->npages = npages;
 332         span->freelist = nil;
 333         span->ref = 0;
 334         span->sizeclass = 0;
 335         span->state = 0;
 336 }
 337
 338 // Initialize an empty doubly-linked list.
 339 void
 340 runtime_MSpanList_Init(MSpan *list)
 341 {
 342         list->state = MSpanListHead;
 343         list->next = list;
 344         list->prev = list;
 345 }
 346
 347 void
 348 runtime_MSpanList_Remove(MSpan *span)
 349 {
 350         if(span->prev == nil && span->next == nil)
 351                 return;
 352         span->prev->next = span->next;
 353         span->next->prev = span->prev;
 354         span->prev = nil;
 355         span->next = nil;
 356 }
 357
 358 bool
 359 runtime_MSpanList_IsEmpty(MSpan *list)
 360 {
 361         return list->next == list;
 362 }
 363
 364 void
 365 runtime_MSpanList_Insert(MSpan *list, MSpan *span)
 366 {
 367         if(span->next != nil || span->prev != nil) {
 368                 // runtime_printf("failed MSpanList_Insert %p %p %p\n", span, span->next, span->prev);
 369                 runtime_throw("MSpanList_Insert");
 370         }
 371         span->next = list->next;
 372         span->prev = list;
 373         span->next->prev = span;
 374         span->prev->next = span;
 375 }
 376
 377