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         MSpan **all;
  31         uint32 cap;
  32
  33         h = vh;
  34         s = (MSpan*)p;
  35         if(h->nspan >= h->nspancap) {
  36                 cap = 64*1024/sizeof(all[0]);
  37                 if(cap < h->nspancap*3/2)
  38                         cap = h->nspancap*3/2;
  39                 all = (MSpan**)runtime_SysAlloc(cap*sizeof(all[0]));
  40                 if(h->allspans) {
  41                         runtime_memmove(all, h->allspans, h->nspancap*sizeof(all[0]));
  42                         runtime_SysFree(h->allspans, h->nspancap*sizeof(all[0]));
  43                 }
  44                 h->allspans = all;
  45                 h->nspancap = cap;
  46         }
  47         h->allspans[h->nspan++] = s;
  48 }
  49
  50 // Initialize the heap; fetch memory using alloc.
  51 void
  52 runtime_MHeap_Init(MHeap *h, void *(*alloc)(uintptr))
  53 {
  54         uint32 i;
  55
  56         runtime_FixAlloc_Init(&h->spanalloc, sizeof(MSpan), alloc, RecordSpan, h);
  57         runtime_FixAlloc_Init(&h->cachealloc, sizeof(MCache), alloc, nil, nil);
  58         // h->mapcache needs no init
  59         for(i=0; i<nelem(h->free); i++)
  60                 runtime_MSpanList_Init(&h->free[i]);
  61         runtime_MSpanList_Init(&h->large);
  62         for(i=0; i<nelem(h->central); i++)
  63                 runtime_MCentral_Init(&h->central[i], i);
  64 }
  65
  66 // Allocate a new span of npage pages from the heap
  67 // and record its size class in the HeapMap and HeapMapCache.
  68 MSpan*
  69 runtime_MHeap_Alloc(MHeap *h, uintptr npage, int32 sizeclass, int32 acct, int32 zeroed)
  70 {
  71         MSpan *s;
  72
  73         runtime_lock(h);
  74         runtime_purgecachedstats(runtime_m()->mcache);
  75         s = MHeap_AllocLocked(h, npage, sizeclass);
  76         if(s != nil) {
  77                 mstats.heap_inuse += npage<<PageShift;
  78                 if(acct) {
  79                         mstats.heap_objects++;
  80                         mstats.heap_alloc += npage<<PageShift;
  81                 }
  82         }
  83         runtime_unlock(h);
  84         if(s != nil && *(uintptr*)(s->start<<PageShift) != 0 && zeroed)
  85                 runtime_memclr((byte*)(s->start<<PageShift), s->npages<<PageShift);
  86         return s;
  87 }
  88
  89 static MSpan*
  90 MHeap_AllocLocked(MHeap *h, uintptr npage, int32 sizeclass)
  91 {
  92         uintptr n;
  93         MSpan *s, *t;
  94         PageID p;
  95
  96         // Try in fixed-size lists up to max.
  97         for(n=npage; n < nelem(h->free); n++) {
  98                 if(!runtime_MSpanList_IsEmpty(&h->free[n])) {
  99                         s = h->free[n].next;
 100                         goto HaveSpan;
 101                 }
 102         }
 103
 104         // Best fit in list of large spans.
 105         if((s = MHeap_AllocLarge(h, npage)) == nil) {
 106                 if(!MHeap_Grow(h, npage))
 107                         return nil;
 108                 if((s = MHeap_AllocLarge(h, npage)) == nil)
 109                         return nil;
 110         }
 111
 112 HaveSpan:
 113         // Mark span in use.
 114         if(s->state != MSpanFree)
 115                 runtime_throw("MHeap_AllocLocked - MSpan not free");
 116         if(s->npages < npage)
 117                 runtime_throw("MHeap_AllocLocked - bad npages");
 118         runtime_MSpanList_Remove(s);
 119         s->state = MSpanInUse;
 120         mstats.heap_idle -= s->npages<<PageShift;
 121         mstats.heap_released -= s->npreleased<<PageShift;
 122         s->npreleased = 0;
 123
 124         if(s->npages > npage) {
 125                 // Trim extra and put it back in the heap.
 126                 t = runtime_FixAlloc_Alloc(&h->spanalloc);
 127                 mstats.mspan_inuse = h->spanalloc.inuse;
 128                 mstats.mspan_sys = h->spanalloc.sys;
 129                 runtime_MSpan_Init(t, s->start + npage, s->npages - npage);
 130                 s->npages = npage;
 131                 p = t->start;
 132                 if(sizeof(void*) == 8)
 133                         p -= ((uintptr)h->arena_start>>PageShift);
 134                 if(p > 0)
 135                         h->map[p-1] = s;
 136                 h->map[p] = t;
 137                 h->map[p+t->npages-1] = t;
 138                 *(uintptr*)(t->start<<PageShift) = *(uintptr*)(s->start<<PageShift);  // copy "needs zeroing" mark
 139                 t->state = MSpanInUse;
 140                 MHeap_FreeLocked(h, t);
 141                 t->unusedsince = s->unusedsince; // preserve age
 142         }
 143         s->unusedsince = 0;
 144
 145         // Record span info, because gc needs to be
 146         // able to map interior pointer to containing span.
 147         s->sizeclass = sizeclass;
 148         s->elemsize = (sizeclass==0 ? s->npages<<PageShift : (uintptr)runtime_class_to_size[sizeclass]);
 149         s->types.compression = MTypes_Empty;
 150         p = s->start;
 151         if(sizeof(void*) == 8)
 152                 p -= ((uintptr)h->arena_start>>PageShift);
 153         for(n=0; n<npage; n++)
 154                 h->map[p+n] = s;
 155         return s;
 156 }
 157
 158 // Allocate a span of exactly npage pages from the list of large spans.
 159 static MSpan*
 160 MHeap_AllocLarge(MHeap *h, uintptr npage)
 161 {
 162         return BestFit(&h->large, npage, nil);
 163 }
 164
 165 // Search list for smallest span with >= npage pages.
 166 // If there are multiple smallest spans, take the one
 167 // with the earliest starting address.
 168 static MSpan*
 169 BestFit(MSpan *list, uintptr npage, MSpan *best)
 170 {
 171         MSpan *s;
 172
 173         for(s=list->next; s != list; s=s->next) {
 174                 if(s->npages < npage)
 175                         continue;
 176                 if(best == nil
 177                 || s->npages < best->npages
 178                 || (s->npages == best->npages && s->start < best->start))
 179                         best = s;
 180         }
 181         return best;
 182 }
 183
 184 // Try to add at least npage pages of memory to the heap,
 185 // returning whether it worked.
 186 static bool
 187 MHeap_Grow(MHeap *h, uintptr npage)
 188 {
 189         uintptr ask;
 190         void *v;
 191         MSpan *s;
 192         PageID p;
 193
 194         // Ask for a big chunk, to reduce the number of mappings
 195         // the operating system needs to track; also amortizes
 196         // the overhead of an operating system mapping.
 197         // Allocate a multiple of 64kB (16 pages).
 198         npage = (npage+15)&~15;
 199         ask = npage<<PageShift;
 200         if(ask < HeapAllocChunk)
 201                 ask = HeapAllocChunk;
 202
 203         v = runtime_MHeap_SysAlloc(h, ask);
 204         if(v == nil) {
 205                 if(ask > (npage<<PageShift)) {
 206                         ask = npage<<PageShift;
 207                         v = runtime_MHeap_SysAlloc(h, ask);
 208                 }
 209                 if(v == nil) {
 210                         runtime_printf("runtime: out of memory: cannot allocate %D-byte block (%D in use)\n", (uint64)ask, mstats.heap_sys);
 211                         return false;
 212                 }
 213         }
 214         mstats.heap_sys += ask;
 215
 216         // Create a fake "in use" span and free it, so that the
 217         // right coalescing happens.
 218         s = runtime_FixAlloc_Alloc(&h->spanalloc);
 219         mstats.mspan_inuse = h->spanalloc.inuse;
 220         mstats.mspan_sys = h->spanalloc.sys;
 221         runtime_MSpan_Init(s, (uintptr)v>>PageShift, ask>>PageShift);
 222         p = s->start;
 223         if(sizeof(void*) == 8)
 224                 p -= ((uintptr)h->arena_start>>PageShift);
 225         h->map[p] = s;
 226         h->map[p + s->npages - 1] = s;
 227         s->state = MSpanInUse;
 228         MHeap_FreeLocked(h, s);
 229         return true;
 230 }
 231
 232 // Look up the span at the given address.
 233 // Address is guaranteed to be in map
 234 // and is guaranteed to be start or end of span.
 235 MSpan*
 236 runtime_MHeap_Lookup(MHeap *h, void *v)
 237 {
 238         uintptr p;
 239
 240         p = (uintptr)v;
 241         if(sizeof(void*) == 8)
 242                 p -= (uintptr)h->arena_start;
 243         return h->map[p >> PageShift];
 244 }
 245
 246 // Look up the span at the given address.
 247 // Address is *not* guaranteed to be in map
 248 // and may be anywhere in the span.
 249 // Map entries for the middle of a span are only
 250 // valid for allocated spans.  Free spans may have
 251 // other garbage in their middles, so we have to
 252 // check for that.
 253 MSpan*
 254 runtime_MHeap_LookupMaybe(MHeap *h, void *v)
 255 {
 256         MSpan *s;
 257         PageID p, q;
 258
 259         if((byte*)v < h->arena_start || (byte*)v >= h->arena_used)
 260                 return nil;
 261         p = (uintptr)v>>PageShift;
 262         q = p;
 263         if(sizeof(void*) == 8)
 264                 q -= (uintptr)h->arena_start >> PageShift;
 265         s = h->map[q];
 266         if(s == nil || p < s->start || p - s->start >= s->npages)
 267                 return nil;
 268         if(s->state != MSpanInUse)
 269                 return nil;
 270         return s;
 271 }
 272
 273 // Free the span back into the heap.
 274 void
 275 runtime_MHeap_Free(MHeap *h, MSpan *s, int32 acct)
 276 {
 277         runtime_lock(h);
 278         runtime_purgecachedstats(runtime_m()->mcache);
 279         mstats.heap_inuse -= s->npages<<PageShift;
 280         if(acct) {
 281                 mstats.heap_alloc -= s->npages<<PageShift;
 282                 mstats.heap_objects--;
 283         }
 284         MHeap_FreeLocked(h, s);
 285         runtime_unlock(h);
 286 }
 287
 288 static void
 289 MHeap_FreeLocked(MHeap *h, MSpan *s)
 290 {
 291         uintptr *sp, *tp;
 292         MSpan *t;
 293         PageID p;
 294
 295         if(s->types.sysalloc)
 296                 runtime_settype_sysfree(s);
 297         s->types.compression = MTypes_Empty;
 298
 299         if(s->state != MSpanInUse || s->ref != 0) {
 300                 runtime_printf("MHeap_FreeLocked - span %p ptr %p state %d ref %d\n", s, s->start<<PageShift, s->state, s->ref);
 301                 runtime_throw("MHeap_FreeLocked - invalid free");
 302         }
 303         mstats.heap_idle += s->npages<<PageShift;
 304         s->state = MSpanFree;
 305         runtime_MSpanList_Remove(s);
 306         sp = (uintptr*)(s->start<<PageShift);
 307         // Stamp newly unused spans. The scavenger will use that
 308         // info to potentially give back some pages to the OS.
 309         s->unusedsince = runtime_nanotime();
 310         s->npreleased = 0;
 311
 312         // Coalesce with earlier, later spans.
 313         p = s->start;
 314         if(sizeof(void*) == 8)
 315                 p -= (uintptr)h->arena_start >> PageShift;
 316         if(p > 0 && (t = h->map[p-1]) != nil && t->state != MSpanInUse) {
 317                 tp = (uintptr*)(t->start<<PageShift);
 318                 *tp |= *sp;     // propagate "needs zeroing" mark
 319                 s->start = t->start;
 320                 s->npages += t->npages;
 321                 s->npreleased = t->npreleased; // absorb released pages
 322                 p -= t->npages;
 323                 h->map[p] = s;
 324                 runtime_MSpanList_Remove(t);
 325                 t->state = MSpanDead;
 326                 runtime_FixAlloc_Free(&h->spanalloc, t);
 327                 mstats.mspan_inuse = h->spanalloc.inuse;
 328                 mstats.mspan_sys = h->spanalloc.sys;
 329         }
 330         if(p+s->npages < nelem(h->map) && (t = h->map[p+s->npages]) != nil && t->state != MSpanInUse) {
 331                 tp = (uintptr*)(t->start<<PageShift);
 332                 *sp |= *tp;     // propagate "needs zeroing" mark
 333                 s->npages += t->npages;
 334                 s->npreleased += t->npreleased;
 335                 h->map[p + s->npages - 1] = s;
 336                 runtime_MSpanList_Remove(t);
 337                 t->state = MSpanDead;
 338                 runtime_FixAlloc_Free(&h->spanalloc, t);
 339                 mstats.mspan_inuse = h->spanalloc.inuse;
 340                 mstats.mspan_sys = h->spanalloc.sys;
 341         }
 342
 343         // Insert s into appropriate list.
 344         if(s->npages < nelem(h->free))
 345                 runtime_MSpanList_Insert(&h->free[s->npages], s);
 346         else
 347                 runtime_MSpanList_Insert(&h->large, s);
 348 }
 349
 350 static void
 351 forcegchelper(void *vnote)
 352 {
 353         Note *note = (Note*)vnote;
 354
 355         runtime_gc(1);
 356         runtime_notewakeup(note);
 357 }
 358
 359 // Release (part of) unused memory to OS.
 360 // Goroutine created at startup.
 361 // Loop forever.
 362 void
 363 runtime_MHeap_Scavenger(void* dummy)
 364 {
 365         MHeap *h;
 366         MSpan *s, *list;
 367         uint64 tick, now, forcegc, limit;
 368         uint32 k, i;
 369         uintptr released, sumreleased;
 370         const byte *env;
 371         bool trace;
 372         Note note, *notep;
 373
 374         USED(dummy);
 375
 376         // If we go two minutes without a garbage collection, force one to run.
 377         forcegc = 2*60*1e9;
 378         // If a span goes unused for 5 minutes after a garbage collection,
 379         // we hand it back to the operating system.
 380         limit = 5*60*1e9;
 381         // Make wake-up period small enough for the sampling to be correct.
 382         if(forcegc < limit)
 383                 tick = forcegc/2;
 384         else
 385                 tick = limit/2;
 386
 387         trace = false;
 388         env = runtime_getenv("GOGCTRACE");
 389         if(env != nil)
 390                 trace = runtime_atoi(env) > 0;
 391
 392         h = &runtime_mheap;
 393         for(k=0;; k++) {
 394                 runtime_noteclear(&note);
 395                 runtime_entersyscall();
 396                 runtime_notetsleep(&note, tick);
 397                 runtime_exitsyscall();
 398
 399                 runtime_lock(h);
 400                 now = runtime_nanotime();
 401                 if(now - mstats.last_gc > forcegc) {
 402                         runtime_unlock(h);
 403                         // The scavenger can not block other goroutines,
 404                         // otherwise deadlock detector can fire spuriously.
 405                         // GC blocks other goroutines via the runtime_worldsema.
 406                         runtime_noteclear(&note);
 407                         notep = &note;
 408                         __go_go(forcegchelper, (void*)notep);
 409                         runtime_entersyscall();
 410                         runtime_notesleep(&note);
 411                         runtime_exitsyscall();
 412                         if(trace)
 413                                 runtime_printf("scvg%d: GC forced\n", k);
 414                         runtime_lock(h);
 415                         now = runtime_nanotime();
 416                 }
 417                 sumreleased = 0;
 418                 for(i=0; i < nelem(h->free)+1; i++) {
 419                         if(i < nelem(h->free))
 420                                 list = &h->free[i];
 421                         else
 422                                 list = &h->large;
 423                         if(runtime_MSpanList_IsEmpty(list))
 424                                 continue;
 425                         for(s=list->next; s != list; s=s->next) {
 426                                 if((now - s->unusedsince) > limit) {
 427                                         released = (s->npages - s->npreleased) << PageShift;
 428                                         mstats.heap_released += released;
 429                                         sumreleased += released;
 430                                         s->npreleased = s->npages;
 431                                         runtime_SysUnused((void*)(s->start << PageShift), s->npages << PageShift);
 432                                 }
 433                         }
 434                 }
 435                 runtime_unlock(h);
 436
 437                 if(trace) {
 438                         if(sumreleased > 0)
 439                                 runtime_printf("scvg%d: %p MB released\n", k, sumreleased>>20);
 440                         runtime_printf("scvg%d: inuse: %D, idle: %D, sys: %D, released: %D, consumed: %D (MB)\n",
 441                                 k, mstats.heap_inuse>>20, mstats.heap_idle>>20, mstats.heap_sys>>20,
 442                                 mstats.heap_released>>20, (mstats.heap_sys - mstats.heap_released)>>20);
 443                 }
 444         }
 445 }
 446
 447 // Initialize a new span with the given start and npages.
 448 void
 449 runtime_MSpan_Init(MSpan *span, PageID start, uintptr npages)
 450 {
 451         span->next = nil;
 452         span->prev = nil;
 453         span->start = start;
 454         span->npages = npages;
 455         span->freelist = nil;
 456         span->ref = 0;
 457         span->sizeclass = 0;
 458         span->elemsize = 0;
 459         span->state = 0;
 460         span->unusedsince = 0;
 461         span->npreleased = 0;
 462         span->types.compression = MTypes_Empty;
 463 }
 464
 465 // Initialize an empty doubly-linked list.
 466 void
 467 runtime_MSpanList_Init(MSpan *list)
 468 {
 469         list->state = MSpanListHead;
 470         list->next = list;
 471         list->prev = list;
 472 }
 473
 474 void
 475 runtime_MSpanList_Remove(MSpan *span)
 476 {
 477         if(span->prev == nil && span->next == nil)
 478                 return;
 479         span->prev->next = span->next;
 480         span->next->prev = span->prev;
 481         span->prev = nil;
 482         span->next = nil;
 483 }
 484
 485 bool
 486 runtime_MSpanList_IsEmpty(MSpan *list)
 487 {
 488         return list->next == list;
 489 }
 490
 491 void
 492 runtime_MSpanList_Insert(MSpan *list, MSpan *span)
 493 {
 494         if(span->next != nil || span->prev != nil) {
 495                 runtime_printf("failed MSpanList_Insert %p %p %p\n", span, span->next, span->prev);
 496                 runtime_throw("MSpanList_Insert");
 497         }
 498         span->next = list->next;
 499         span->prev = list;
 500         span->next->prev = span;
 501         span->prev->next = span;
 502 }
 503
 504