libgo/runtime/malloc.goc

   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 // See malloc.h for overview.
   6 //
   7 // TODO(rsc): double-check stats.
   8
   9 package runtime
  10 #include <stddef.h>
  11 #include <errno.h>
  12 #include <stdlib.h>
  13 #include "go-alloc.h"
  14 #include "runtime.h"
  15 #include "arch.h"
  16 #include "malloc.h"
  17 #include "go-string.h"
  18 #include "interface.h"
  19 #include "go-type.h"
  20
  21 MHeap runtime_mheap;
  22
  23 extern MStats mstats;   // defined in extern.go
  24
  25 extern volatile int32 runtime_MemProfileRate
  26   __asm__ ("runtime.MemProfileRate");
  27
  28 // Allocate an object of at least size bytes.
  29 // Small objects are allocated from the per-thread cache's free lists.
  30 // Large objects (> 32 kB) are allocated straight from the heap.
  31 void*
  32 runtime_mallocgc(uintptr size, uint32 flag, int32 dogc, int32 zeroed)
  33 {
  34         M *m;
  35         G *g;
  36         int32 sizeclass, rate;
  37         MCache *c;
  38         uintptr npages;
  39         MSpan *s;
  40         void *v;
  41
  42         m = runtime_m();
  43         g = runtime_g();
  44         if(g->status == Gsyscall)
  45                 dogc = 0;
  46         if(runtime_gcwaiting && g != m->g0 && m->locks == 0 && g->status != Gsyscall) {
  47                 runtime_gosched();
  48                 m = runtime_m();
  49         }
  50         if(m->mallocing)
  51                 runtime_throw("malloc/free - deadlock");
  52         m->mallocing = 1;
  53         if(size == 0)
  54                 size = 1;
  55
  56         c = m->mcache;
  57         c->local_nmalloc++;
  58         if(size <= MaxSmallSize) {
  59                 // Allocate from mcache free lists.
  60                 sizeclass = runtime_SizeToClass(size);
  61                 size = runtime_class_to_size[sizeclass];
  62                 v = runtime_MCache_Alloc(c, sizeclass, size, zeroed);
  63                 if(v == nil)
  64                         runtime_throw("out of memory");
  65                 c->local_alloc += size;
  66                 c->local_total_alloc += size;
  67                 c->local_by_size[sizeclass].nmalloc++;
  68         } else {
  69                 // TODO(rsc): Report tracebacks for very large allocations.
  70
  71                 // Allocate directly from heap.
  72                 npages = size >> PageShift;
  73                 if((size & PageMask) != 0)
  74                         npages++;
  75                 s = runtime_MHeap_Alloc(&runtime_mheap, npages, 0, 1);
  76                 if(s == nil)
  77                         runtime_throw("out of memory");
  78                 size = npages<<PageShift;
  79                 c->local_alloc += size;
  80                 c->local_total_alloc += size;
  81                 v = (void*)(s->start << PageShift);
  82
  83                 // setup for mark sweep
  84                 runtime_markspan(v, 0, 0, true);
  85         }
  86         if(!(flag & FlagNoGC))
  87                 runtime_markallocated(v, size, (flag&FlagNoPointers) != 0);
  88
  89         m->mallocing = 0;
  90
  91         if(!(flag & FlagNoProfiling) && (rate = runtime_MemProfileRate) > 0) {
  92                 if(size >= (uint32) rate)
  93                         goto profile;
  94                 if((uint32) m->mcache->next_sample > size)
  95                         m->mcache->next_sample -= size;
  96                 else {
  97                         // pick next profile time
  98                         // If you change this, also change allocmcache.
  99                         if(rate > 0x3fffffff)   // make 2*rate not overflow
 100                                 rate = 0x3fffffff;
 101                         m->mcache->next_sample = runtime_fastrand1() % (2*rate);
 102                 profile:
 103                         runtime_setblockspecial(v, true);
 104                         runtime_MProf_Malloc(v, size);
 105                 }
 106         }
 107
 108         if(dogc && mstats.heap_alloc >= mstats.next_gc)
 109                 runtime_gc(0);
 110         return v;
 111 }
 112
 113 void*
 114 __go_alloc(uintptr size)
 115 {
 116         return runtime_mallocgc(size, 0, 0, 1);
 117 }
 118
 119 // Free the object whose base pointer is v.
 120 void
 121 __go_free(void *v)
 122 {
 123         M *m;
 124         int32 sizeclass;
 125         MSpan *s;
 126         MCache *c;
 127         uint32 prof;
 128         uintptr size;
 129
 130         if(v == nil)
 131                 return;
 132
 133         // If you change this also change mgc0.c:/^sweep,
 134         // which has a copy of the guts of free.
 135
 136         m = runtime_m();
 137         if(m->mallocing)
 138                 runtime_throw("malloc/free - deadlock");
 139         m->mallocing = 1;
 140
 141         if(!runtime_mlookup(v, nil, nil, &s)) {
 142                 runtime_printf("free %p: not an allocated block\n", v);
 143                 runtime_throw("free runtime_mlookup");
 144         }
 145         prof = runtime_blockspecial(v);
 146
 147         // Find size class for v.
 148         sizeclass = s->sizeclass;
 149         c = m->mcache;
 150         if(sizeclass == 0) {
 151                 // Large object.
 152                 size = s->npages<<PageShift;
 153                 *(uintptr*)(s->start<<PageShift) = 1;   // mark as "needs to be zeroed"
 154                 // Must mark v freed before calling unmarkspan and MHeap_Free:
 155                 // they might coalesce v into other spans and change the bitmap further.
 156                 runtime_markfreed(v, size);
 157                 runtime_unmarkspan(v, 1<<PageShift);
 158                 runtime_MHeap_Free(&runtime_mheap, s, 1);
 159         } else {
 160                 // Small object.
 161                 size = runtime_class_to_size[sizeclass];
 162                 if(size > sizeof(uintptr))
 163                         ((uintptr*)v)[1] = 1;   // mark as "needs to be zeroed"
 164                 // Must mark v freed before calling MCache_Free:
 165                 // it might coalesce v and other blocks into a bigger span
 166                 // and change the bitmap further.
 167                 runtime_markfreed(v, size);
 168                 c->local_by_size[sizeclass].nfree++;
 169                 runtime_MCache_Free(c, v, sizeclass, size);
 170         }
 171         c->local_nfree++;
 172         c->local_alloc -= size;
 173         if(prof)
 174                 runtime_MProf_Free(v, size);
 175         m->mallocing = 0;
 176 }
 177
 178 int32
 179 runtime_mlookup(void *v, byte **base, uintptr *size, MSpan **sp)
 180 {
 181         uintptr n, i;
 182         byte *p;
 183         MSpan *s;
 184
 185         runtime_m()->mcache->local_nlookup++;
 186         s = runtime_MHeap_LookupMaybe(&runtime_mheap, v);
 187         if(sp)
 188                 *sp = s;
 189         if(s == nil) {
 190                 runtime_checkfreed(v, 1);
 191                 if(base)
 192                         *base = nil;
 193                 if(size)
 194                         *size = 0;
 195                 return 0;
 196         }
 197
 198         p = (byte*)((uintptr)s->start<<PageShift);
 199         if(s->sizeclass == 0) {
 200                 // Large object.
 201                 if(base)
 202                         *base = p;
 203                 if(size)
 204                         *size = s->npages<<PageShift;
 205                 return 1;
 206         }
 207
 208         if((byte*)v >= (byte*)s->limit) {
 209                 // pointers past the last block do not count as pointers.
 210                 return 0;
 211         }
 212
 213         n = runtime_class_to_size[s->sizeclass];
 214         if(base) {
 215                 i = ((byte*)v - p)/n;
 216                 *base = p + i*n;
 217         }
 218         if(size)
 219                 *size = n;
 220
 221         return 1;
 222 }
 223
 224 MCache*
 225 runtime_allocmcache(void)
 226 {
 227         int32 rate;
 228         MCache *c;
 229
 230         runtime_lock(&runtime_mheap);
 231         c = runtime_FixAlloc_Alloc(&runtime_mheap.cachealloc);
 232         mstats.mcache_inuse = runtime_mheap.cachealloc.inuse;
 233         mstats.mcache_sys = runtime_mheap.cachealloc.sys;
 234         runtime_unlock(&runtime_mheap);
 235
 236         // Set first allocation sample size.
 237         rate = runtime_MemProfileRate;
 238         if(rate > 0x3fffffff)   // make 2*rate not overflow
 239                 rate = 0x3fffffff;
 240         if(rate != 0)
 241                 c->next_sample = runtime_fastrand1() % (2*rate);
 242
 243         return c;
 244 }
 245
 246 void
 247 runtime_purgecachedstats(M* m)
 248 {
 249         MCache *c;
 250
 251         // Protected by either heap or GC lock.
 252         c = m->mcache;
 253         mstats.heap_alloc += c->local_cachealloc;
 254         c->local_cachealloc = 0;
 255         mstats.heap_objects += c->local_objects;
 256         c->local_objects = 0;
 257         mstats.nmalloc += c->local_nmalloc;
 258         c->local_nmalloc = 0;
 259         mstats.nfree += c->local_nfree;
 260         c->local_nfree = 0;
 261         mstats.nlookup += c->local_nlookup;
 262         c->local_nlookup = 0;
 263         mstats.alloc += c->local_alloc;
 264         c->local_alloc= 0;
 265         mstats.total_alloc += c->local_total_alloc;
 266         c->local_total_alloc= 0;
 267 }
 268
 269 extern uintptr runtime_sizeof_C_MStats
 270   __asm__ ("runtime.Sizeof_C_MStats");
 271
 272 #define MaxArena32 (2U<<30)
 273
 274 void
 275 runtime_mallocinit(void)
 276 {
 277         byte *p;
 278         uintptr arena_size, bitmap_size;
 279         extern byte end[];
 280         byte *want;
 281         uintptr limit;
 282
 283         runtime_sizeof_C_MStats = sizeof(MStats);
 284
 285         p = nil;
 286         arena_size = 0;
 287         bitmap_size = 0;
 288
 289         // for 64-bit build
 290         USED(p);
 291         USED(arena_size);
 292         USED(bitmap_size);
 293
 294         runtime_InitSizes();
 295
 296         limit = runtime_memlimit();
 297
 298         // Set up the allocation arena, a contiguous area of memory where
 299         // allocated data will be found.  The arena begins with a bitmap large
 300         // enough to hold 4 bits per allocated word.
 301         if(sizeof(void*) == 8 && (limit == 0 || limit > (1<<30))) {
 302                 // On a 64-bit machine, allocate from a single contiguous reservation.
 303                 // 16 GB should be big enough for now.
 304                 //
 305                 // The code will work with the reservation at any address, but ask
 306                 // SysReserve to use 0x000000f800000000 if possible.
 307                 // Allocating a 16 GB region takes away 36 bits, and the amd64
 308                 // doesn't let us choose the top 17 bits, so that leaves the 11 bits
 309                 // in the middle of 0x00f8 for us to choose.  Choosing 0x00f8 means
 310                 // that the valid memory addresses will begin 0x00f8, 0x00f9, 0x00fa, 0x00fb.
 311                 // None of the bytes f8 f9 fa fb can appear in valid UTF-8, and
 312                 // they are otherwise as far from ff (likely a common byte) as possible.
 313                 // Choosing 0x00 for the leading 6 bits was more arbitrary, but it
 314                 // is not a common ASCII code point either.  Using 0x11f8 instead
 315                 // caused out of memory errors on OS X during thread allocations.
 316                 // These choices are both for debuggability and to reduce the
 317                 // odds of the conservative garbage collector not collecting memory
 318                 // because some non-pointer block of memory had a bit pattern
 319                 // that matched a memory address.
 320                 //
 321                 // Actually we reserve 17 GB (because the bitmap ends up being 1 GB)
 322                 // but it hardly matters: fc is not valid UTF-8 either, and we have to
 323                 // allocate 15 GB before we get that far.
 324                 //
 325                 // If this fails we fall back to the 32 bit memory mechanism
 326                 arena_size = (uintptr)(16LL<<30);
 327                 bitmap_size = arena_size / (sizeof(void*)*8/4);
 328                 p = runtime_SysReserve((void*)(0x00f8ULL<<32), bitmap_size + arena_size);
 329         }
 330         if (p == nil) {
 331                 // On a 32-bit machine, we can't typically get away
 332                 // with a giant virtual address space reservation.
 333                 // Instead we map the memory information bitmap
 334                 // immediately after the data segment, large enough
 335                 // to handle another 2GB of mappings (256 MB),
 336                 // along with a reservation for another 512 MB of memory.
 337                 // When that gets used up, we'll start asking the kernel
 338                 // for any memory anywhere and hope it's in the 2GB
 339                 // following the bitmap (presumably the executable begins
 340                 // near the bottom of memory, so we'll have to use up
 341                 // most of memory before the kernel resorts to giving out
 342                 // memory before the beginning of the text segment).
 343                 //
 344                 // Alternatively we could reserve 512 MB bitmap, enough
 345                 // for 4GB of mappings, and then accept any memory the
 346                 // kernel threw at us, but normally that's a waste of 512 MB
 347                 // of address space, which is probably too much in a 32-bit world.
 348                 bitmap_size = MaxArena32 / (sizeof(void*)*8/4);
 349                 arena_size = 512<<20;
 350                 if(limit > 0 && arena_size+bitmap_size > limit) {
 351                         bitmap_size = (limit / 9) & ~((1<<PageShift) - 1);
 352                         arena_size = bitmap_size * 8;
 353                 }
 354
 355                 // SysReserve treats the address we ask for, end, as a hint,
 356                 // not as an absolute requirement.  If we ask for the end
 357                 // of the data segment but the operating system requires
 358                 // a little more space before we can start allocating, it will
 359                 // give out a slightly higher pointer.  Except QEMU, which
 360                 // is buggy, as usual: it won't adjust the pointer upward.
 361                 // So adjust it upward a little bit ourselves: 1/4 MB to get
 362                 // away from the running binary image and then round up
 363                 // to a MB boundary.
 364                 want = (byte*)(((uintptr)end + (1<<18) + (1<<20) - 1)&~((1<<20)-1));
 365                 if(0xffffffff - (uintptr)want <= bitmap_size + arena_size)
 366                   want = 0;
 367                 p = runtime_SysReserve(want, bitmap_size + arena_size);
 368                 if(p == nil)
 369                         runtime_throw("runtime: cannot reserve arena virtual address space");
 370                 if((uintptr)p & (((uintptr)1<<PageShift)-1))
 371                         runtime_printf("runtime: SysReserve returned unaligned address %p; asked for %p", p, bitmap_size+arena_size);
 372         }
 373         if((uintptr)p & (((uintptr)1<<PageShift)-1))
 374                 runtime_throw("runtime: SysReserve returned unaligned address");
 375
 376         runtime_mheap.bitmap = p;
 377         runtime_mheap.arena_start = p + bitmap_size;
 378         runtime_mheap.arena_used = runtime_mheap.arena_start;
 379         runtime_mheap.arena_end = runtime_mheap.arena_start + arena_size;
 380
 381         // Initialize the rest of the allocator.
 382         runtime_MHeap_Init(&runtime_mheap, runtime_SysAlloc);
 383         runtime_m()->mcache = runtime_allocmcache();
 384
 385         // See if it works.
 386         runtime_free(runtime_malloc(1));
 387 }
 388
 389 void*
 390 runtime_MHeap_SysAlloc(MHeap *h, uintptr n)
 391 {
 392         byte *p;
 393
 394
 395         if(n > (uintptr)(h->arena_end - h->arena_used)) {
 396                 // We are in 32-bit mode, maybe we didn't use all possible address space yet.
 397                 // Reserve some more space.
 398                 byte *new_end;
 399                 uintptr needed;
 400
 401                 needed = (uintptr)h->arena_used + n - (uintptr)h->arena_end;
 402                 // Round wanted arena size to a multiple of 256MB.
 403                 needed = (needed + (256<<20) - 1) & ~((256<<20)-1);
 404                 new_end = h->arena_end + needed;
 405                 if(new_end <= h->arena_start + MaxArena32) {
 406                         p = runtime_SysReserve(h->arena_end, new_end - h->arena_end);
 407                         if(p == h->arena_end)
 408                                 h->arena_end = new_end;
 409                 }
 410         }
 411         if(n <= (uintptr)(h->arena_end - h->arena_used)) {
 412                 // Keep taking from our reservation.
 413                 p = h->arena_used;
 414                 runtime_SysMap(p, n);
 415                 h->arena_used += n;
 416                 runtime_MHeap_MapBits(h);
 417                 return p;
 418         }
 419
 420         // If using 64-bit, our reservation is all we have.
 421         if(sizeof(void*) == 8 && (uintptr)h->bitmap >= 0xffffffffU)
 422                 return nil;
 423
 424         // On 32-bit, once the reservation is gone we can
 425         // try to get memory at a location chosen by the OS
 426         // and hope that it is in the range we allocated bitmap for.
 427         p = runtime_SysAlloc(n);
 428         if(p == nil)
 429                 return nil;
 430
 431         if(p < h->arena_start || (uintptr)(p+n - h->arena_start) >= MaxArena32) {
 432                 runtime_printf("runtime: memory allocated by OS (%p) not in usable range [%p,%p)\n",
 433                         p, h->arena_start, h->arena_start+MaxArena32);
 434                 runtime_SysFree(p, n);
 435                 return nil;
 436         }
 437
 438         if(p+n > h->arena_used) {
 439                 h->arena_used = p+n;
 440                 if(h->arena_used > h->arena_end)
 441                         h->arena_end = h->arena_used;
 442                 runtime_MHeap_MapBits(h);
 443         }
 444
 445         return p;
 446 }
 447
 448 // Runtime stubs.
 449
 450 void*
 451 runtime_mal(uintptr n)
 452 {
 453         return runtime_mallocgc(n, 0, 1, 1);
 454 }
 455
 456 func new(typ *Type) (ret *uint8) {
 457         uint32 flag = typ->__code&GO_NO_POINTERS ? FlagNoPointers : 0;
 458         ret = runtime_mallocgc(typ->__size, flag, 1, 1);
 459 }
 460
 461 func GC() {
 462         runtime_gc(1);
 463 }
 464
 465 func SetFinalizer(obj Eface, finalizer Eface) {
 466         byte *base;
 467         uintptr size;
 468         const FuncType *ft;
 469
 470         if(obj.__type_descriptor == nil) {
 471                 runtime_printf("runtime.SetFinalizer: first argument is nil interface\n");
 472                 goto throw;
 473         }
 474         if(obj.__type_descriptor->__code != GO_PTR) {
 475                 runtime_printf("runtime.SetFinalizer: first argument is %S, not pointer\n", *obj.__type_descriptor->__reflection);
 476                 goto throw;
 477         }
 478         if(!runtime_mlookup(obj.__object, &base, &size, nil) || obj.__object != base) {
 479                 runtime_printf("runtime.SetFinalizer: pointer not at beginning of allocated block\n");
 480                 goto throw;
 481         }
 482         ft = nil;
 483         if(finalizer.__type_descriptor != nil) {
 484                 if(finalizer.__type_descriptor->__code != GO_FUNC)
 485                         goto badfunc;
 486                 ft = (const FuncType*)finalizer.__type_descriptor;
 487                 if(ft->__dotdotdot || ft->__in.__count != 1 || !__go_type_descriptors_equal(*(Type**)ft->__in.__values, obj.__type_descriptor))
 488                         goto badfunc;
 489         }
 490
 491         if(!runtime_addfinalizer(obj.__object, finalizer.__type_descriptor != nil ? *(void**)finalizer.__object : nil, ft)) {
 492                 runtime_printf("runtime.SetFinalizer: finalizer already set\n");
 493                 goto throw;
 494         }
 495         return;
 496
 497 badfunc:
 498         runtime_printf("runtime.SetFinalizer: second argument is %S, not func(%S)\n", *finalizer.__type_descriptor->__reflection, *obj.__type_descriptor->__reflection);
 499 throw:
 500         runtime_throw("runtime.SetFinalizer");
 501 }