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         mstats.heap_released -= s->npreleased<<PageShift;
 107         s->npreleased = 0;
 108
 109         if(s->npages > npage) {
 110                 // Trim extra and put it back in the heap.
 111                 t = runtime_FixAlloc_Alloc(&h->spanalloc);
 112                 mstats.mspan_inuse = h->spanalloc.inuse;
 113                 mstats.mspan_sys = h->spanalloc.sys;
 114                 runtime_MSpan_Init(t, s->start + npage, s->npages - npage);
 115                 s->npages = npage;
 116                 p = t->start;
 117                 if(sizeof(void*) == 8)
 118                         p -= ((uintptr)h->arena_start>>PageShift);
 119                 if(p > 0)
 120                         h->map[p-1] = s;
 121                 h->map[p] = t;
 122                 h->map[p+t->npages-1] = t;
 123                 *(uintptr*)(t->start<<PageShift) = *(uintptr*)(s->start<<PageShift);  // copy "needs zeroing" mark
 124                 t->state = MSpanInUse;
 125                 MHeap_FreeLocked(h, t);
 126         }
 127
 128         if(*(uintptr*)(s->start<<PageShift) != 0)
 129                 runtime_memclr((byte*)(s->start<<PageShift), s->npages<<PageShift);
 130
 131         // Record span info, because gc needs to be
 132         // able to map interior pointer to containing span.
 133         s->sizeclass = sizeclass;
 134         p = s->start;
 135         if(sizeof(void*) == 8)
 136                 p -= ((uintptr)h->arena_start>>PageShift);
 137         for(n=0; n<npage; n++)
 138                 h->map[p+n] = s;
 139         return s;
 140 }
 141
 142 // Allocate a span of exactly npage pages from the list of large spans.
 143 static MSpan*
 144 MHeap_AllocLarge(MHeap *h, uintptr npage)
 145 {
 146         return BestFit(&h->large, npage, nil);
 147 }
 148
 149 // Search list for smallest span with >= npage pages.
 150 // If there are multiple smallest spans, take the one
 151 // with the earliest starting address.
 152 static MSpan*
 153 BestFit(MSpan *list, uintptr npage, MSpan *best)
 154 {
 155         MSpan *s;
 156
 157         for(s=list->next; s != list; s=s->next) {
 158                 if(s->npages < npage)
 159                         continue;
 160                 if(best == nil
 161                 || s->npages < best->npages
 162                 || (s->npages == best->npages && s->start < best->start))
 163                         best = s;
 164         }
 165         return best;
 166 }
 167
 168 // Try to add at least npage pages of memory to the heap,
 169 // returning whether it worked.
 170 static bool
 171 MHeap_Grow(MHeap *h, uintptr npage)
 172 {
 173         uintptr ask;
 174         void *v;
 175         MSpan *s;
 176         PageID p;
 177
 178         // Ask for a big chunk, to reduce the number of mappings
 179         // the operating system needs to track; also amortizes
 180         // the overhead of an operating system mapping.
 181         // Allocate a multiple of 64kB (16 pages).
 182         npage = (npage+15)&~15;
 183         ask = npage<<PageShift;
 184         if(ask < HeapAllocChunk)
 185                 ask = HeapAllocChunk;
 186
 187         v = runtime_MHeap_SysAlloc(h, ask);
 188         if(v == nil) {
 189                 if(ask > (npage<<PageShift)) {
 190                         ask = npage<<PageShift;
 191                         v = runtime_MHeap_SysAlloc(h, ask);
 192                 }
 193                 if(v == nil) {
 194                         runtime_printf("runtime: out of memory: cannot allocate %D-byte block (%D in use)\n", (uint64)ask, mstats.heap_sys);
 195                         return false;
 196                 }
 197         }
 198         mstats.heap_sys += ask;
 199
 200         // Create a fake "in use" span and free it, so that the
 201         // right coalescing happens.
 202         s = runtime_FixAlloc_Alloc(&h->spanalloc);
 203         mstats.mspan_inuse = h->spanalloc.inuse;
 204         mstats.mspan_sys = h->spanalloc.sys;
 205         runtime_MSpan_Init(s, (uintptr)v>>PageShift, ask>>PageShift);
 206         p = s->start;
 207         if(sizeof(void*) == 8)
 208                 p -= ((uintptr)h->arena_start>>PageShift);
 209         h->map[p] = s;
 210         h->map[p + s->npages - 1] = s;
 211         s->state = MSpanInUse;
 212         MHeap_FreeLocked(h, s);
 213         return true;
 214 }
 215
 216 // Look up the span at the given address.
 217 // Address is guaranteed to be in map
 218 // and is guaranteed to be start or end of span.
 219 MSpan*
 220 runtime_MHeap_Lookup(MHeap *h, void *v)
 221 {
 222         uintptr p;
 223
 224         p = (uintptr)v;
 225         if(sizeof(void*) == 8)
 226                 p -= (uintptr)h->arena_start;
 227         return h->map[p >> PageShift];
 228 }
 229
 230 // Look up the span at the given address.
 231 // Address is *not* guaranteed to be in map
 232 // and may be anywhere in the span.
 233 // Map entries for the middle of a span are only
 234 // valid for allocated spans.  Free spans may have
 235 // other garbage in their middles, so we have to
 236 // check for that.
 237 MSpan*
 238 runtime_MHeap_LookupMaybe(MHeap *h, void *v)
 239 {
 240         MSpan *s;
 241         PageID p, q;
 242
 243         if((byte*)v < h->arena_start || (byte*)v >= h->arena_used)
 244                 return nil;
 245         p = (uintptr)v>>PageShift;
 246         q = p;
 247         if(sizeof(void*) == 8)
 248                 q -= (uintptr)h->arena_start >> PageShift;
 249         s = h->map[q];
 250         if(s == nil || p < s->start || p - s->start >= s->npages)
 251                 return nil;
 252         if(s->state != MSpanInUse)
 253                 return nil;
 254         return s;
 255 }
 256
 257 // Free the span back into the heap.
 258 void
 259 runtime_MHeap_Free(MHeap *h, MSpan *s, int32 acct)
 260 {
 261         runtime_lock(h);
 262         runtime_purgecachedstats(runtime_m());
 263         mstats.heap_inuse -= s->npages<<PageShift;
 264         if(acct) {
 265                 mstats.heap_alloc -= s->npages<<PageShift;
 266                 mstats.heap_objects--;
 267         }
 268         MHeap_FreeLocked(h, s);
 269         runtime_unlock(h);
 270 }
 271
 272 static void
 273 MHeap_FreeLocked(MHeap *h, MSpan *s)
 274 {
 275         uintptr *sp, *tp;
 276         MSpan *t;
 277         PageID p;
 278
 279         if(s->state != MSpanInUse || s->ref != 0) {
 280                 runtime_printf("MHeap_FreeLocked - span %p ptr %p state %d ref %d\n", s, s->start<<PageShift, s->state, s->ref);
 281                 runtime_throw("MHeap_FreeLocked - invalid free");
 282         }
 283         mstats.heap_idle += s->npages<<PageShift;
 284         s->state = MSpanFree;
 285         s->unusedsince = 0;
 286         s->npreleased = 0;
 287         runtime_MSpanList_Remove(s);
 288         sp = (uintptr*)(s->start<<PageShift);
 289
 290         // Coalesce with earlier, later spans.
 291         p = s->start;
 292         if(sizeof(void*) == 8)
 293                 p -= (uintptr)h->arena_start >> PageShift;
 294         if(p > 0 && (t = h->map[p-1]) != nil && t->state != MSpanInUse) {
 295                 tp = (uintptr*)(t->start<<PageShift);
 296                 *tp |= *sp;     // propagate "needs zeroing" mark
 297                 s->start = t->start;
 298                 s->npages += t->npages;
 299                 s->npreleased = t->npreleased; // absorb released pages
 300                 p -= t->npages;
 301                 h->map[p] = s;
 302                 runtime_MSpanList_Remove(t);
 303                 t->state = MSpanDead;
 304                 runtime_FixAlloc_Free(&h->spanalloc, t);
 305                 mstats.mspan_inuse = h->spanalloc.inuse;
 306                 mstats.mspan_sys = h->spanalloc.sys;
 307         }
 308         if(p+s->npages < nelem(h->map) && (t = h->map[p+s->npages]) != nil && t->state != MSpanInUse) {
 309                 tp = (uintptr*)(t->start<<PageShift);
 310                 *sp |= *tp;     // propagate "needs zeroing" mark
 311                 s->npages += t->npages;
 312                 s->npreleased += t->npreleased;
 313                 h->map[p + s->npages - 1] = s;
 314                 runtime_MSpanList_Remove(t);
 315                 t->state = MSpanDead;
 316                 runtime_FixAlloc_Free(&h->spanalloc, t);
 317                 mstats.mspan_inuse = h->spanalloc.inuse;
 318                 mstats.mspan_sys = h->spanalloc.sys;
 319         }
 320
 321         // Insert s into appropriate list.
 322         if(s->npages < nelem(h->free))
 323                 runtime_MSpanList_Insert(&h->free[s->npages], s);
 324         else
 325                 runtime_MSpanList_Insert(&h->large, s);
 326 }
 327
 328 // Release (part of) unused memory to OS.
 329 // Goroutine created at startup.
 330 // Loop forever.
 331 void
 332 runtime_MHeap_Scavenger(void* dummy)
 333 {
 334         MHeap *h;
 335         MSpan *s, *list;
 336         uint64 tick, now, forcegc, limit;
 337         uint32 k, i;
 338         uintptr released, sumreleased;
 339         const byte *env;
 340         bool trace;
 341         Note note;
 342
 343         USED(dummy);
 344
 345         // If we go two minutes without a garbage collection, force one to run.
 346         forcegc = 2*60*1e9;
 347         // If a span goes unused for 5 minutes after a garbage collection,
 348         // we hand it back to the operating system.
 349         limit = 5*60*1e9;
 350         // Make wake-up period small enough for the sampling to be correct.
 351         if(forcegc < limit)
 352                 tick = forcegc/2;
 353         else
 354                 tick = limit/2;
 355
 356         trace = false;
 357         env = runtime_getenv("GOGCTRACE");
 358         if(env != nil)
 359                 trace = runtime_atoi(env) > 0;
 360
 361         h = &runtime_mheap;
 362         for(k=0;; k++) {
 363                 runtime_noteclear(&note);
 364                 runtime_entersyscall();
 365                 runtime_notetsleep(&note, tick);
 366                 runtime_exitsyscall();
 367
 368                 runtime_lock(h);
 369                 now = runtime_nanotime();
 370                 if(now - mstats.last_gc > forcegc) {
 371                         runtime_unlock(h);
 372                         runtime_gc(1);
 373                         runtime_lock(h);
 374                         now = runtime_nanotime();
 375                         if (trace)
 376                                 runtime_printf("scvg%d: GC forced\n", k);
 377                 }
 378                 sumreleased = 0;
 379                 for(i=0; i < nelem(h->free)+1; i++) {
 380                         if(i < nelem(h->free))
 381                                 list = &h->free[i];
 382                         else
 383                                 list = &h->large;
 384                         if(runtime_MSpanList_IsEmpty(list))
 385                                 continue;
 386                         for(s=list->next; s != list; s=s->next) {
 387                                 if(s->unusedsince != 0 && (now - s->unusedsince) > limit) {
 388                                         released = (s->npages - s->npreleased) << PageShift;
 389                                         mstats.heap_released += released;
 390                                         sumreleased += released;
 391                                         s->npreleased = s->npages;
 392                                         runtime_SysUnused((void*)(s->start << PageShift), s->npages << PageShift);
 393                                 }
 394                         }
 395                 }
 396                 runtime_unlock(h);
 397
 398                 if(trace) {
 399                         if(sumreleased > 0)
 400                                 runtime_printf("scvg%d: %p MB released\n", k, sumreleased>>20);
 401                         runtime_printf("scvg%d: inuse: %D, idle: %D, sys: %D, released: %D, consumed: %D (MB)\n",
 402                                 k, mstats.heap_inuse>>20, mstats.heap_idle>>20, mstats.heap_sys>>20,
 403                                 mstats.heap_released>>20, (mstats.heap_sys - mstats.heap_released)>>20);
 404                 }
 405         }
 406 }
 407
 408 // Initialize a new span with the given start and npages.
 409 void
 410 runtime_MSpan_Init(MSpan *span, PageID start, uintptr npages)
 411 {
 412         span->next = nil;
 413         span->prev = nil;
 414         span->start = start;
 415         span->npages = npages;
 416         span->freelist = nil;
 417         span->ref = 0;
 418         span->sizeclass = 0;
 419         span->state = 0;
 420         span->unusedsince = 0;
 421         span->npreleased = 0;
 422 }
 423
 424 // Initialize an empty doubly-linked list.
 425 void
 426 runtime_MSpanList_Init(MSpan *list)
 427 {
 428         list->state = MSpanListHead;
 429         list->next = list;
 430         list->prev = list;
 431 }
 432
 433 void
 434 runtime_MSpanList_Remove(MSpan *span)
 435 {
 436         if(span->prev == nil && span->next == nil)
 437                 return;
 438         span->prev->next = span->next;
 439         span->next->prev = span->prev;
 440         span->prev = nil;
 441         span->next = nil;
 442 }
 443
 444 bool
 445 runtime_MSpanList_IsEmpty(MSpan *list)
 446 {
 447         return list->next == list;
 448 }
 449
 450 void
 451 runtime_MSpanList_Insert(MSpan *list, MSpan *span)
 452 {
 453         if(span->next != nil || span->prev != nil) {
 454                 runtime_printf("failed MSpanList_Insert %p %p %p\n", span, span->next, span->prev);
 455                 runtime_throw("MSpanList_Insert");
 456         }
 457         span->next = list->next;
 458         span->prev = list;
 459         span->next->prev = span;
 460         span->prev->next = span;
 461 }
 462
 463