contrib/jemalloc/src/pages.c

   1 #define JEMALLOC_PAGES_C_
   2 #include "jemalloc/internal/jemalloc_preamble.h"
   3
   4 #include "jemalloc/internal/pages.h"
   5
   6 #include "jemalloc/internal/jemalloc_internal_includes.h"
   7
   8 #include "jemalloc/internal/assert.h"
   9 #include "jemalloc/internal/malloc_io.h"
  10
  11 #ifdef JEMALLOC_SYSCTL_VM_OVERCOMMIT
  12 #include <sys/sysctl.h>
  13 #ifdef __FreeBSD__
  14 #include <vm/vm_param.h>
  15 #endif
  16 #endif
  17
  18 /******************************************************************************/
  19 /* Data. */
  20
  21 /* Actual operating system page size, detected during bootstrap, <= PAGE. */
  22 static size_t   os_page;
  23
  24 #ifndef _WIN32
  25 #  define PAGES_PROT_COMMIT (PROT_READ | PROT_WRITE)
  26 #  define PAGES_PROT_DECOMMIT (PROT_NONE)
  27 static int      mmap_flags;
  28 #endif
  29 static bool     os_overcommits;
  30
  31 const char *thp_mode_names[] = {
  32         "default",
  33         "always",
  34         "never",
  35         "not supported"
  36 };
  37 thp_mode_t opt_thp = THP_MODE_DEFAULT;
  38 thp_mode_t init_system_thp_mode;
  39
  40 /* Runtime support for lazy purge. Irrelevant when !pages_can_purge_lazy. */
  41 static bool pages_can_purge_lazy_runtime = true;
  42
  43 /******************************************************************************/
  44 /*
  45  * Function prototypes for static functions that are referenced prior to
  46  * definition.
  47  */
  48
  49 static void os_pages_unmap(void *addr, size_t size);
  50
  51 /******************************************************************************/
  52
  53 static void *
  54 os_pages_map(void *addr, size_t size, size_t alignment, bool *commit) {
  55         assert(ALIGNMENT_ADDR2BASE(addr, os_page) == addr);
  56         assert(ALIGNMENT_CEILING(size, os_page) == size);
  57         assert(size != 0);
  58
  59         if (os_overcommits) {
  60                 *commit = true;
  61         }
  62
  63         void *ret;
  64 #ifdef _WIN32
  65         /*
  66          * If VirtualAlloc can't allocate at the given address when one is
  67          * given, it fails and returns NULL.
  68          */
  69         ret = VirtualAlloc(addr, size, MEM_RESERVE | (*commit ? MEM_COMMIT : 0),
  70             PAGE_READWRITE);
  71 #else
  72         /*
  73          * We don't use MAP_FIXED here, because it can cause the *replacement*
  74          * of existing mappings, and we only want to create new mappings.
  75          */
  76         {
  77                 int prot = *commit ? PAGES_PROT_COMMIT : PAGES_PROT_DECOMMIT;
  78
  79                 ret = mmap(addr, size, prot, mmap_flags, -1, 0);
  80         }
  81         assert(ret != NULL);
  82
  83         if (ret == MAP_FAILED) {
  84                 ret = NULL;
  85         } else if (addr != NULL && ret != addr) {
  86                 /*
  87                  * We succeeded in mapping memory, but not in the right place.
  88                  */
  89                 os_pages_unmap(ret, size);
  90                 ret = NULL;
  91         }
  92 #endif
  93         assert(ret == NULL || (addr == NULL && ret != addr) || (addr != NULL &&
  94             ret == addr));
  95         return ret;
  96 }
  97
  98 static void *
  99 os_pages_trim(void *addr, size_t alloc_size, size_t leadsize, size_t size,
 100     bool *commit) {
 101         void *ret = (void *)((uintptr_t)addr + leadsize);
 102
 103         assert(alloc_size >= leadsize + size);
 104 #ifdef _WIN32
 105         os_pages_unmap(addr, alloc_size);
 106         void *new_addr = os_pages_map(ret, size, PAGE, commit);
 107         if (new_addr == ret) {
 108                 return ret;
 109         }
 110         if (new_addr != NULL) {
 111                 os_pages_unmap(new_addr, size);
 112         }
 113         return NULL;
 114 #else
 115         size_t trailsize = alloc_size - leadsize - size;
 116
 117         if (leadsize != 0) {
 118                 os_pages_unmap(addr, leadsize);
 119         }
 120         if (trailsize != 0) {
 121                 os_pages_unmap((void *)((uintptr_t)ret + size), trailsize);
 122         }
 123         return ret;
 124 #endif
 125 }
 126
 127 static void
 128 os_pages_unmap(void *addr, size_t size) {
 129         assert(ALIGNMENT_ADDR2BASE(addr, os_page) == addr);
 130         assert(ALIGNMENT_CEILING(size, os_page) == size);
 131
 132 #ifdef _WIN32
 133         if (VirtualFree(addr, 0, MEM_RELEASE) == 0)
 134 #else
 135         if (munmap(addr, size) == -1)
 136 #endif
 137         {
 138                 char buf[BUFERROR_BUF];
 139
 140                 buferror(get_errno(), buf, sizeof(buf));
 141                 malloc_printf("<jemalloc>: Error in "
 142 #ifdef _WIN32
 143                     "VirtualFree"
 144 #else
 145                     "munmap"
 146 #endif
 147                     "(): %s\n", buf);
 148                 if (opt_abort) {
 149                         abort();
 150                 }
 151         }
 152 }
 153
 154 static void *
 155 pages_map_slow(size_t size, size_t alignment, bool *commit) {
 156         size_t alloc_size = size + alignment - os_page;
 157         /* Beware size_t wrap-around. */
 158         if (alloc_size < size) {
 159                 return NULL;
 160         }
 161
 162         void *ret;
 163         do {
 164                 void *pages = os_pages_map(NULL, alloc_size, alignment, commit);
 165                 if (pages == NULL) {
 166                         return NULL;
 167                 }
 168                 size_t leadsize = ALIGNMENT_CEILING((uintptr_t)pages, alignment)
 169                     - (uintptr_t)pages;
 170                 ret = os_pages_trim(pages, alloc_size, leadsize, size, commit);
 171         } while (ret == NULL);
 172
 173         assert(ret != NULL);
 174         assert(PAGE_ADDR2BASE(ret) == ret);
 175         return ret;
 176 }
 177
 178 void *
 179 pages_map(void *addr, size_t size, size_t alignment, bool *commit) {
 180         assert(alignment >= PAGE);
 181         assert(ALIGNMENT_ADDR2BASE(addr, alignment) == addr);
 182
 183 #if defined(__FreeBSD__) && defined(MAP_EXCL)
 184         /*
 185          * FreeBSD has mechanisms both to mmap at specific address without
 186          * touching existing mappings, and to mmap with specific alignment.
 187          */
 188         {
 189                 if (os_overcommits) {
 190                         *commit = true;
 191                 }
 192
 193                 int prot = *commit ? PAGES_PROT_COMMIT : PAGES_PROT_DECOMMIT;
 194                 int flags = mmap_flags;
 195
 196                 if (addr != NULL) {
 197                         flags |= MAP_FIXED | MAP_EXCL;
 198                 } else {
 199                         unsigned alignment_bits = ffs_zu(alignment);
 200                         assert(alignment_bits > 1);
 201                         flags |= MAP_ALIGNED(alignment_bits - 1);
 202                 }
 203
 204                 void *ret = mmap(addr, size, prot, flags, -1, 0);
 205                 if (ret == MAP_FAILED) {
 206                         ret = NULL;
 207                 }
 208
 209                 return ret;
 210         }
 211 #endif
 212         /*
 213          * Ideally, there would be a way to specify alignment to mmap() (like
 214          * NetBSD has), but in the absence of such a feature, we have to work
 215          * hard to efficiently create aligned mappings.  The reliable, but
 216          * slow method is to create a mapping that is over-sized, then trim the
 217          * excess.  However, that always results in one or two calls to
 218          * os_pages_unmap(), and it can leave holes in the process's virtual
 219          * memory map if memory grows downward.
 220          *
 221          * Optimistically try mapping precisely the right amount before falling
 222          * back to the slow method, with the expectation that the optimistic
 223          * approach works most of the time.
 224          */
 225
 226         void *ret = os_pages_map(addr, size, os_page, commit);
 227         if (ret == NULL || ret == addr) {
 228                 return ret;
 229         }
 230         assert(addr == NULL);
 231         if (ALIGNMENT_ADDR2OFFSET(ret, alignment) != 0) {
 232                 os_pages_unmap(ret, size);
 233                 return pages_map_slow(size, alignment, commit);
 234         }
 235
 236         assert(PAGE_ADDR2BASE(ret) == ret);
 237         return ret;
 238 }
 239
 240 void
 241 pages_unmap(void *addr, size_t size) {
 242         assert(PAGE_ADDR2BASE(addr) == addr);
 243         assert(PAGE_CEILING(size) == size);
 244
 245         os_pages_unmap(addr, size);
 246 }
 247
 248 static bool
 249 pages_commit_impl(void *addr, size_t size, bool commit) {
 250         assert(PAGE_ADDR2BASE(addr) == addr);
 251         assert(PAGE_CEILING(size) == size);
 252
 253         if (os_overcommits) {
 254                 return true;
 255         }
 256
 257 #ifdef _WIN32
 258         return (commit ? (addr != VirtualAlloc(addr, size, MEM_COMMIT,
 259             PAGE_READWRITE)) : (!VirtualFree(addr, size, MEM_DECOMMIT)));
 260 #else
 261         {
 262                 int prot = commit ? PAGES_PROT_COMMIT : PAGES_PROT_DECOMMIT;
 263                 void *result = mmap(addr, size, prot, mmap_flags | MAP_FIXED,
 264                     -1, 0);
 265                 if (result == MAP_FAILED) {
 266                         return true;
 267                 }
 268                 if (result != addr) {
 269                         /*
 270                          * We succeeded in mapping memory, but not in the right
 271                          * place.
 272                          */
 273                         os_pages_unmap(result, size);
 274                         return true;
 275                 }
 276                 return false;
 277         }
 278 #endif
 279 }
 280
 281 bool
 282 pages_commit(void *addr, size_t size) {
 283         return pages_commit_impl(addr, size, true);
 284 }
 285
 286 bool
 287 pages_decommit(void *addr, size_t size) {
 288         return pages_commit_impl(addr, size, false);
 289 }
 290
 291 bool
 292 pages_purge_lazy(void *addr, size_t size) {
 293         assert(PAGE_ADDR2BASE(addr) == addr);
 294         assert(PAGE_CEILING(size) == size);
 295
 296         if (!pages_can_purge_lazy) {
 297                 return true;
 298         }
 299         if (!pages_can_purge_lazy_runtime) {
 300                 /*
 301                  * Built with lazy purge enabled, but detected it was not
 302                  * supported on the current system.
 303                  */
 304                 return true;
 305         }
 306
 307 #ifdef _WIN32
 308         VirtualAlloc(addr, size, MEM_RESET, PAGE_READWRITE);
 309         return false;
 310 #elif defined(JEMALLOC_PURGE_MADVISE_FREE)
 311         return (madvise(addr, size,
 312 #  ifdef MADV_FREE
 313             MADV_FREE
 314 #  else
 315             JEMALLOC_MADV_FREE
 316 #  endif
 317             ) != 0);
 318 #elif defined(JEMALLOC_PURGE_MADVISE_DONTNEED) && \
 319     !defined(JEMALLOC_PURGE_MADVISE_DONTNEED_ZEROS)
 320         return (madvise(addr, size, MADV_DONTNEED) != 0);
 321 #else
 322         not_reached();
 323 #endif
 324 }
 325
 326 bool
 327 pages_purge_forced(void *addr, size_t size) {
 328         assert(PAGE_ADDR2BASE(addr) == addr);
 329         assert(PAGE_CEILING(size) == size);
 330
 331         if (!pages_can_purge_forced) {
 332                 return true;
 333         }
 334
 335 #if defined(JEMALLOC_PURGE_MADVISE_DONTNEED) && \
 336     defined(JEMALLOC_PURGE_MADVISE_DONTNEED_ZEROS)
 337         return (madvise(addr, size, MADV_DONTNEED) != 0);
 338 #elif defined(JEMALLOC_MAPS_COALESCE)
 339         /* Try to overlay a new demand-zeroed mapping. */
 340         return pages_commit(addr, size);
 341 #else
 342         not_reached();
 343 #endif
 344 }
 345
 346 static bool
 347 pages_huge_impl(void *addr, size_t size, bool aligned) {
 348         if (aligned) {
 349                 assert(HUGEPAGE_ADDR2BASE(addr) == addr);
 350                 assert(HUGEPAGE_CEILING(size) == size);
 351         }
 352 #ifdef JEMALLOC_HAVE_MADVISE_HUGE
 353         return (madvise(addr, size, MADV_HUGEPAGE) != 0);
 354 #else
 355         return true;
 356 #endif
 357 }
 358
 359 bool
 360 pages_huge(void *addr, size_t size) {
 361         return pages_huge_impl(addr, size, true);
 362 }
 363
 364 static bool
 365 pages_huge_unaligned(void *addr, size_t size) {
 366         return pages_huge_impl(addr, size, false);
 367 }
 368
 369 static bool
 370 pages_nohuge_impl(void *addr, size_t size, bool aligned) {
 371         if (aligned) {
 372                 assert(HUGEPAGE_ADDR2BASE(addr) == addr);
 373                 assert(HUGEPAGE_CEILING(size) == size);
 374         }
 375
 376 #ifdef JEMALLOC_HAVE_MADVISE_HUGE
 377         return (madvise(addr, size, MADV_NOHUGEPAGE) != 0);
 378 #else
 379         return false;
 380 #endif
 381 }
 382
 383 bool
 384 pages_nohuge(void *addr, size_t size) {
 385         return pages_nohuge_impl(addr, size, true);
 386 }
 387
 388 static bool
 389 pages_nohuge_unaligned(void *addr, size_t size) {
 390         return pages_nohuge_impl(addr, size, false);
 391 }
 392
 393 bool
 394 pages_dontdump(void *addr, size_t size) {
 395         assert(PAGE_ADDR2BASE(addr) == addr);
 396         assert(PAGE_CEILING(size) == size);
 397 #ifdef JEMALLOC_MADVISE_DONTDUMP
 398         return madvise(addr, size, MADV_DONTDUMP) != 0;
 399 #else
 400         return false;
 401 #endif
 402 }
 403
 404 bool
 405 pages_dodump(void *addr, size_t size) {
 406         assert(PAGE_ADDR2BASE(addr) == addr);
 407         assert(PAGE_CEILING(size) == size);
 408 #ifdef JEMALLOC_MADVISE_DONTDUMP
 409         return madvise(addr, size, MADV_DODUMP) != 0;
 410 #else
 411         return false;
 412 #endif
 413 }
 414
 415
 416 static size_t
 417 os_page_detect(void) {
 418 #ifdef _WIN32
 419         SYSTEM_INFO si;
 420         GetSystemInfo(&si);
 421         return si.dwPageSize;
 422 #elif defined(__FreeBSD__)
 423         return getpagesize();
 424 #else
 425         long result = sysconf(_SC_PAGESIZE);
 426         if (result == -1) {
 427                 return LG_PAGE;
 428         }
 429         return (size_t)result;
 430 #endif
 431 }
 432
 433 #ifdef JEMALLOC_SYSCTL_VM_OVERCOMMIT
 434 static bool
 435 os_overcommits_sysctl(void) {
 436         int vm_overcommit;
 437         size_t sz;
 438
 439         sz = sizeof(vm_overcommit);
 440 #if defined(__FreeBSD__) && defined(VM_OVERCOMMIT)
 441         int mib[2];
 442
 443         mib[0] = CTL_VM;
 444         mib[1] = VM_OVERCOMMIT;
 445         if (sysctl(mib, 2, &vm_overcommit, &sz, NULL, 0) != 0) {
 446                 return false; /* Error. */
 447         }
 448 #else
 449         if (sysctlbyname("vm.overcommit", &vm_overcommit, &sz, NULL, 0) != 0) {
 450                 return false; /* Error. */
 451         }
 452 #endif
 453
 454         return ((vm_overcommit & 0x3) == 0);
 455 }
 456 #endif
 457
 458 #ifdef JEMALLOC_PROC_SYS_VM_OVERCOMMIT_MEMORY
 459 /*
 460  * Use syscall(2) rather than {open,read,close}(2) when possible to avoid
 461  * reentry during bootstrapping if another library has interposed system call
 462  * wrappers.
 463  */
 464 static bool
 465 os_overcommits_proc(void) {
 466         int fd;
 467         char buf[1];
 468
 469 #if defined(JEMALLOC_USE_SYSCALL) && defined(SYS_open)
 470         #if defined(O_CLOEXEC)
 471                 fd = (int)syscall(SYS_open, "/proc/sys/vm/overcommit_memory", O_RDONLY |
 472                         O_CLOEXEC);
 473         #else
 474                 fd = (int)syscall(SYS_open, "/proc/sys/vm/overcommit_memory", O_RDONLY);
 475                 if (fd != -1) {
 476                         fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
 477                 }
 478         #endif
 479 #elif defined(JEMALLOC_USE_SYSCALL) && defined(SYS_openat)
 480         #if defined(O_CLOEXEC)
 481                 fd = (int)syscall(SYS_openat,
 482                         AT_FDCWD, "/proc/sys/vm/overcommit_memory", O_RDONLY | O_CLOEXEC);
 483         #else
 484                 fd = (int)syscall(SYS_openat,
 485                         AT_FDCWD, "/proc/sys/vm/overcommit_memory", O_RDONLY);
 486                 if (fd != -1) {
 487                         fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
 488                 }
 489         #endif
 490 #else
 491         #if defined(O_CLOEXEC)
 492                 fd = open("/proc/sys/vm/overcommit_memory", O_RDONLY | O_CLOEXEC);
 493         #else
 494                 fd = open("/proc/sys/vm/overcommit_memory", O_RDONLY);
 495                 if (fd != -1) {
 496                         fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
 497                 }
 498         #endif
 499 #endif
 500
 501         if (fd == -1) {
 502                 return false; /* Error. */
 503         }
 504
 505         ssize_t nread = malloc_read_fd(fd, &buf, sizeof(buf));
 506 #if defined(JEMALLOC_USE_SYSCALL) && defined(SYS_close)
 507         syscall(SYS_close, fd);
 508 #else
 509         close(fd);
 510 #endif
 511
 512         if (nread < 1) {
 513                 return false; /* Error. */
 514         }
 515         /*
 516          * /proc/sys/vm/overcommit_memory meanings:
 517          * 0: Heuristic overcommit.
 518          * 1: Always overcommit.
 519          * 2: Never overcommit.
 520          */
 521         return (buf[0] == '0' || buf[0] == '1');
 522 }
 523 #endif
 524
 525 void
 526 pages_set_thp_state (void *ptr, size_t size) {
 527         if (opt_thp == thp_mode_default || opt_thp == init_system_thp_mode) {
 528                 return;
 529         }
 530         assert(opt_thp != thp_mode_not_supported &&
 531             init_system_thp_mode != thp_mode_not_supported);
 532
 533         if (opt_thp == thp_mode_always
 534             && init_system_thp_mode != thp_mode_never) {
 535                 assert(init_system_thp_mode == thp_mode_default);
 536                 pages_huge_unaligned(ptr, size);
 537         } else if (opt_thp == thp_mode_never) {
 538                 assert(init_system_thp_mode == thp_mode_default ||
 539                     init_system_thp_mode == thp_mode_always);
 540                 pages_nohuge_unaligned(ptr, size);
 541         }
 542 }
 543
 544 static void
 545 init_thp_state(void) {
 546         if (!have_madvise_huge) {
 547                 if (metadata_thp_enabled() && opt_abort) {
 548                         malloc_write("<jemalloc>: no MADV_HUGEPAGE support\n");
 549                         abort();
 550                 }
 551                 goto label_error;
 552         }
 553
 554         static const char sys_state_madvise[] = "always [madvise] never\n";
 555         static const char sys_state_always[] = "[always] madvise never\n";
 556         static const char sys_state_never[] = "always madvise [never]\n";
 557         char buf[sizeof(sys_state_madvise)];
 558
 559 #if defined(JEMALLOC_USE_SYSCALL) && defined(SYS_open)
 560         int fd = (int)syscall(SYS_open,
 561             "/sys/kernel/mm/transparent_hugepage/enabled", O_RDONLY);
 562 #else
 563         int fd = open("/sys/kernel/mm/transparent_hugepage/enabled", O_RDONLY);
 564 #endif
 565         if (fd == -1) {
 566                 goto label_error;
 567         }
 568
 569         ssize_t nread = malloc_read_fd(fd, &buf, sizeof(buf));
 570 #if defined(JEMALLOC_USE_SYSCALL) && defined(SYS_close)
 571         syscall(SYS_close, fd);
 572 #else
 573         close(fd);
 574 #endif
 575
 576         if (strncmp(buf, sys_state_madvise, (size_t)nread) == 0) {
 577                 init_system_thp_mode = thp_mode_default;
 578         } else if (strncmp(buf, sys_state_always, (size_t)nread) == 0) {
 579                 init_system_thp_mode = thp_mode_always;
 580         } else if (strncmp(buf, sys_state_never, (size_t)nread) == 0) {
 581                 init_system_thp_mode = thp_mode_never;
 582         } else {
 583                 goto label_error;
 584         }
 585         return;
 586 label_error:
 587         opt_thp = init_system_thp_mode = thp_mode_not_supported;
 588 }
 589
 590 bool
 591 pages_boot(void) {
 592         os_page = os_page_detect();
 593         if (os_page > PAGE) {
 594                 malloc_write("<jemalloc>: Unsupported system page size\n");
 595                 if (opt_abort) {
 596                         abort();
 597                 }
 598                 return true;
 599         }
 600
 601 #ifndef _WIN32
 602         mmap_flags = MAP_PRIVATE | MAP_ANON;
 603 #endif
 604
 605 #ifdef JEMALLOC_SYSCTL_VM_OVERCOMMIT
 606         os_overcommits = os_overcommits_sysctl();
 607 #elif defined(JEMALLOC_PROC_SYS_VM_OVERCOMMIT_MEMORY)
 608         os_overcommits = os_overcommits_proc();
 609 #  ifdef MAP_NORESERVE
 610         if (os_overcommits) {
 611                 mmap_flags |= MAP_NORESERVE;
 612         }
 613 #  endif
 614 #else
 615         os_overcommits = false;
 616 #endif
 617
 618         init_thp_state();
 619
 620 #ifdef __FreeBSD__
 621         /*
 622          * FreeBSD doesn't need the check; madvise(2) is known to work.
 623          */
 624 #else
 625         /* Detect lazy purge runtime support. */
 626         if (pages_can_purge_lazy) {
 627                 bool committed = false;
 628                 void *madv_free_page = os_pages_map(NULL, PAGE, PAGE, &committed);
 629                 if (madv_free_page == NULL) {
 630                         return true;
 631                 }
 632                 assert(pages_can_purge_lazy_runtime);
 633                 if (pages_purge_lazy(madv_free_page, PAGE)) {
 634                         pages_can_purge_lazy_runtime = false;
 635                 }
 636                 os_pages_unmap(madv_free_page, PAGE);
 637         }
 638 #endif
 639
 640         return false;
 641 }