1 /* 2 * Copyright (c) 2015, 2019, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 */ 23 24 #include "precompiled.hpp" 25 #include "gc/z/zArray.inline.hpp" 26 #include "gc/z/zBackingFile_linux.hpp" 27 #include "gc/z/zBackingPath_linux.hpp" 28 #include "gc/z/zErrno.hpp" 29 #include "gc/z/zGlobals.hpp" 30 #include "gc/z/zLargePages.inline.hpp" 31 #include "gc/z/zSyscall_linux.hpp" 32 #include "logging/log.hpp" 33 #include "runtime/init.hpp" 34 #include "runtime/os.hpp" 35 #include "utilities/align.hpp" 36 #include "utilities/debug.hpp" 37 38 #include <fcntl.h> 39 #include <sys/mman.h> 40 #include <sys/stat.h> 41 #include <sys/statfs.h> 42 #include <sys/types.h> 43 #include <unistd.h> 44 45 // 46 // Support for building on older Linux systems 47 // 48 49 // memfd_create(2) flags 50 #ifndef MFD_CLOEXEC 51 #define MFD_CLOEXEC 0x0001U 52 #endif 53 #ifndef MFD_HUGETLB 54 #define MFD_HUGETLB 0x0004U 55 #endif 56 57 // open(2) flags 58 #ifndef O_CLOEXEC 59 #define O_CLOEXEC 02000000 60 #endif 61 #ifndef O_TMPFILE 62 #define O_TMPFILE (020000000 | O_DIRECTORY) 63 #endif 64 65 // fallocate(2) flags 66 #ifndef FALLOC_FL_KEEP_SIZE 67 #define FALLOC_FL_KEEP_SIZE 0x01 68 #endif 69 #ifndef FALLOC_FL_PUNCH_HOLE 70 #define FALLOC_FL_PUNCH_HOLE 0x02 71 #endif 72 73 // Filesystem types, see statfs(2) 74 #ifndef TMPFS_MAGIC 75 #define TMPFS_MAGIC 0x01021994 76 #endif 77 #ifndef HUGETLBFS_MAGIC 78 #define HUGETLBFS_MAGIC 0x958458f6 79 #endif 80 81 // Filesystem names 82 #define ZFILESYSTEM_TMPFS "tmpfs" 83 #define ZFILESYSTEM_HUGETLBFS "hugetlbfs" 84 85 // Sysfs file for transparent huge page on tmpfs 86 #define ZFILENAME_SHMEM_ENABLED "/sys/kernel/mm/transparent_hugepage/shmem_enabled" 87 88 // Java heap filename 89 #define ZFILENAME_HEAP "java_heap" 90 91 // Preferred tmpfs mount points, ordered by priority 92 static const char* z_preferred_tmpfs_mountpoints[] = { 93 "/dev/shm", 94 "/run/shm", 95 NULL 96 }; 97 98 // Preferred hugetlbfs mount points, ordered by priority 99 static const char* z_preferred_hugetlbfs_mountpoints[] = { 100 "/dev/hugepages", 101 "/hugepages", 102 NULL 103 }; 104 105 static int z_fallocate_hugetlbfs_attempts = 3; 106 static bool z_fallocate_supported = true; 107 108 ZBackingFile::ZBackingFile() : 109 _fd(-1), 110 _size(0), 111 _filesystem(0), 112 _block_size(0), 113 _available(0), 114 _initialized(false) { 115 116 // Create backing file 117 _fd = create_fd(ZFILENAME_HEAP); 118 if (_fd == -1) { 119 return; 120 } 121 122 // Get filesystem statistics 123 struct statfs buf; 124 if (fstatfs(_fd, &buf) == -1) { 125 ZErrno err; 126 log_error(gc)("Failed to determine filesystem type for backing file (%s)", err.to_string()); 127 return; 128 } 129 130 _filesystem = buf.f_type; 131 _block_size = buf.f_bsize; 132 _available = buf.f_bavail * _block_size; 133 134 // Make sure we're on a supported filesystem 135 if (!is_tmpfs() && !is_hugetlbfs()) { 136 log_error(gc)("Backing file must be located on a %s or a %s filesystem", 137 ZFILESYSTEM_TMPFS, ZFILESYSTEM_HUGETLBFS); 138 return; 139 } 140 141 // Make sure the filesystem type matches requested large page type 142 if (ZLargePages::is_transparent() && !is_tmpfs()) { 143 log_error(gc)("-XX:+UseTransparentHugePages can only be enable when using a %s filesystem", 144 ZFILESYSTEM_TMPFS); 145 return; 146 } 147 148 if (ZLargePages::is_transparent() && !tmpfs_supports_transparent_huge_pages()) { 149 log_error(gc)("-XX:+UseTransparentHugePages on a %s filesystem not supported by kernel", 150 ZFILESYSTEM_TMPFS); 151 return; 152 } 153 154 if (ZLargePages::is_explicit() && !is_hugetlbfs()) { 155 log_error(gc)("-XX:+UseLargePages (without -XX:+UseTransparentHugePages) can only be enabled " 156 "when using a %s filesystem", ZFILESYSTEM_HUGETLBFS); 157 return; 158 } 159 160 if (!ZLargePages::is_explicit() && is_hugetlbfs()) { 161 log_error(gc)("-XX:+UseLargePages must be enabled when using a %s filesystem", 162 ZFILESYSTEM_HUGETLBFS); 163 return; 164 } 165 166 const size_t expected_block_size = is_tmpfs() ? os::vm_page_size() : os::large_page_size(); 167 if (expected_block_size != _block_size) { 168 log_error(gc)("%s filesystem has unexpected block size " SIZE_FORMAT " (expected " SIZE_FORMAT ")", 169 is_tmpfs() ? ZFILESYSTEM_TMPFS : ZFILESYSTEM_HUGETLBFS, _block_size, expected_block_size); 170 return; 171 } 172 173 // Successfully initialized 174 _initialized = true; 175 } 176 177 int ZBackingFile::create_mem_fd(const char* name) const { 178 // Create file name 179 char filename[PATH_MAX]; 180 snprintf(filename, sizeof(filename), "%s%s", name, ZLargePages::is_explicit() ? ".hugetlb" : ""); 181 182 // Create file 183 const int extra_flags = ZLargePages::is_explicit() ? MFD_HUGETLB : 0; 184 const int fd = ZSyscall::memfd_create(filename, MFD_CLOEXEC | extra_flags); 185 if (fd == -1) { 186 ZErrno err; 187 log_debug(gc, init)("Failed to create memfd file (%s)", 188 ((ZLargePages::is_explicit() && err == EINVAL) ? "Hugepages not supported" : err.to_string())); 189 return -1; 190 } 191 192 log_info(gc, init)("Heap backed by file: /memfd:%s", filename); 193 194 return fd; 195 } 196 197 int ZBackingFile::create_file_fd(const char* name) const { 198 const char* const filesystem = ZLargePages::is_explicit() 199 ? ZFILESYSTEM_HUGETLBFS 200 : ZFILESYSTEM_TMPFS; 201 const char** const preferred_mountpoints = ZLargePages::is_explicit() 202 ? z_preferred_hugetlbfs_mountpoints 203 : z_preferred_tmpfs_mountpoints; 204 205 // Find mountpoint 206 ZBackingPath path(filesystem, preferred_mountpoints); 207 if (path.get() == NULL) { 208 log_error(gc)("Use -XX:ZPath to specify the path to a %s filesystem", filesystem); 209 return -1; 210 } 211 212 // Try to create an anonymous file using the O_TMPFILE flag. Note that this 213 // flag requires kernel >= 3.11. If this fails we fall back to open/unlink. 214 const int fd_anon = os::open(path.get(), O_TMPFILE|O_EXCL|O_RDWR|O_CLOEXEC, S_IRUSR|S_IWUSR); 215 if (fd_anon == -1) { 216 ZErrno err; 217 log_debug(gc, init)("Failed to create anonymous file in %s (%s)", path.get(), 218 (err == EINVAL ? "Not supported" : err.to_string())); 219 } else { 220 // Get inode number for anonymous file 221 struct stat stat_buf; 222 if (fstat(fd_anon, &stat_buf) == -1) { 223 ZErrno err; 224 log_error(gc)("Failed to determine inode number for anonymous file (%s)", err.to_string()); 225 return -1; 226 } 227 228 log_info(gc, init)("Heap backed by file: %s/#" UINT64_FORMAT, path.get(), (uint64_t)stat_buf.st_ino); 229 230 return fd_anon; 231 } 232 233 log_debug(gc, init)("Falling back to open/unlink"); 234 235 // Create file name 236 char filename[PATH_MAX]; 237 snprintf(filename, sizeof(filename), "%s/%s.%d", path.get(), name, os::current_process_id()); 238 239 // Create file 240 const int fd = os::open(filename, O_CREAT|O_EXCL|O_RDWR|O_CLOEXEC, S_IRUSR|S_IWUSR); 241 if (fd == -1) { 242 ZErrno err; 243 log_error(gc)("Failed to create file %s (%s)", filename, err.to_string()); 244 return -1; 245 } 246 247 // Unlink file 248 if (unlink(filename) == -1) { 249 ZErrno err; 250 log_error(gc)("Failed to unlink file %s (%s)", filename, err.to_string()); 251 return -1; 252 } 253 254 log_info(gc, init)("Heap backed by file: %s", filename); 255 256 return fd; 257 } 258 259 int ZBackingFile::create_fd(const char* name) const { 260 if (ZPath == NULL) { 261 // If the path is not explicitly specified, then we first try to create a memfd file 262 // instead of looking for a tmpfd/hugetlbfs mount point. Note that memfd_create() might 263 // not be supported at all (requires kernel >= 3.17), or it might not support large 264 // pages (requires kernel >= 4.14). If memfd_create() fails, then we try to create a 265 // file on an accessible tmpfs or hugetlbfs mount point. 266 const int fd = create_mem_fd(name); 267 if (fd != -1) { 268 return fd; 269 } 270 271 log_debug(gc, init)("Falling back to searching for an accessible mount point"); 272 } 273 274 return create_file_fd(name); 275 } 276 277 bool ZBackingFile::is_initialized() const { 278 return _initialized; 279 } 280 281 int ZBackingFile::fd() const { 282 return _fd; 283 } 284 285 size_t ZBackingFile::size() const { 286 return _size; 287 } 288 289 size_t ZBackingFile::available() const { 290 return _available; 291 } 292 293 bool ZBackingFile::is_tmpfs() const { 294 return _filesystem == TMPFS_MAGIC; 295 } 296 297 bool ZBackingFile::is_hugetlbfs() const { 298 return _filesystem == HUGETLBFS_MAGIC; 299 } 300 301 bool ZBackingFile::tmpfs_supports_transparent_huge_pages() const { 302 // If the shmem_enabled file exists and is readable then we 303 // know the kernel supports transparent huge pages for tmpfs. 304 return access(ZFILENAME_SHMEM_ENABLED, R_OK) == 0; 305 } 306 307 ZErrno ZBackingFile::fallocate_compat_ftruncate(size_t size) const { 308 while (ftruncate(_fd, size) == -1) { 309 if (errno != EINTR) { 310 // Failed 311 return errno; 312 } 313 } 314 315 // Success 316 return 0; 317 } 318 319 ZErrno ZBackingFile::fallocate_compat_mmap(size_t offset, size_t length, bool touch) const { 320 // On hugetlbfs, mapping a file segment will fail immediately, without 321 // the need to touch the mapped pages first, if there aren't enough huge 322 // pages available to back the mapping. 323 void* const addr = mmap(0, length, PROT_READ|PROT_WRITE, MAP_SHARED, _fd, offset); 324 if (addr == MAP_FAILED) { 325 // Failed 326 return errno; 327 } 328 329 // Once mapped, the huge pages are only reserved. We need to touch them 330 // to associate them with the file segment. Note that we can not punch 331 // hole in file segments which only have reserved pages. 332 if (touch) { 333 char* const start = (char*)addr; 334 char* const end = start + length; 335 os::pretouch_memory(start, end, _block_size); 336 } 337 338 // Unmap again. From now on, the huge pages that were mapped are allocated 339 // to this file. There's no risk in getting SIGBUS when touching them. 340 if (munmap(addr, length) == -1) { 341 // Failed 342 return errno; 343 } 344 345 // Success 346 return 0; 347 } 348 349 ZErrno ZBackingFile::fallocate_compat_pwrite(size_t offset, size_t length) const { 350 uint8_t data = 0; 351 352 // Allocate backing memory by writing to each block 353 for (size_t pos = offset; pos < offset + length; pos += _block_size) { 354 if (pwrite(_fd, &data, sizeof(data), pos) == -1) { 355 // Failed 356 return errno; 357 } 358 } 359 360 // Success 361 return 0; 362 } 363 364 ZErrno ZBackingFile::fallocate_fill_hole_compat(size_t offset, size_t length) { 365 // fallocate(2) is only supported by tmpfs since Linux 3.5, and by hugetlbfs 366 // since Linux 4.3. When fallocate(2) is not supported we emulate it using 367 // ftruncate/pwrite (for tmpfs) or ftruncate/mmap/munmap (for hugetlbfs). 368 369 const size_t end = offset + length; 370 if (end > _size) { 371 // Increase file size 372 const ZErrno err = fallocate_compat_ftruncate(end); 373 if (err) { 374 // Failed 375 return err; 376 } 377 } 378 379 // Allocate backing memory 380 const ZErrno err = is_hugetlbfs() ? fallocate_compat_mmap(offset, length, false /* touch */) 381 : fallocate_compat_pwrite(offset, length); 382 if (err) { 383 if (end > _size) { 384 // Restore file size 385 fallocate_compat_ftruncate(_size); 386 } 387 388 // Failed 389 return err; 390 } 391 392 if (end > _size) { 393 // Record new file size 394 _size = end; 395 } 396 397 // Success 398 return 0; 399 } 400 401 ZErrno ZBackingFile::fallocate_fill_hole_syscall(size_t offset, size_t length) { 402 const int mode = 0; // Allocate 403 const int res = ZSyscall::fallocate(_fd, mode, offset, length); 404 if (res == -1) { 405 // Failed 406 return errno; 407 } 408 409 const size_t end = offset + length; 410 if (end > _size) { 411 // Record new file size 412 _size = end; 413 } 414 415 // Success 416 return 0; 417 } 418 419 ZErrno ZBackingFile::fallocate_fill_hole(size_t offset, size_t length) { 420 // Using compat mode is more efficient when allocating space on hugetlbfs. 421 // Note that allocating huge pages this way will only reserve them, and not 422 // associate them with segments of the file. We must guarantee that we at 423 // some point touch these segments, otherwise we can not punch hole in them. 424 if (z_fallocate_supported && !is_hugetlbfs()) { 425 const ZErrno err = fallocate_fill_hole_syscall(offset, length); 426 if (!err) { 427 // Success 428 return 0; 429 } 430 431 if (err != ENOSYS && err != EOPNOTSUPP) { 432 // Failed 433 return err; 434 } 435 436 // Not supported 437 log_debug(gc)("Falling back to fallocate() compatibility mode"); 438 z_fallocate_supported = false; 439 } 440 441 return fallocate_fill_hole_compat(offset, length); 442 } 443 444 ZErrno ZBackingFile::fallocate_punch_hole(size_t offset, size_t length) { 445 if (is_hugetlbfs()) { 446 // We can only punch hole in pages that have been touched. Non-touched 447 // pages are only reserved, and not associated with any specific file 448 // segment. We don't know which pages have been previously touched, so 449 // we always touch them here to guarantee that we can punch hole. 450 const ZErrno err = fallocate_compat_mmap(offset, length, true /* touch */); 451 if (err) { 452 // Failed 453 return err; 454 } 455 } 456 457 const int mode = FALLOC_FL_PUNCH_HOLE|FALLOC_FL_KEEP_SIZE; 458 if (ZSyscall::fallocate(_fd, mode, offset, length) == -1) { 459 // Failed 460 return errno; 461 } 462 463 // Success 464 return 0; 465 } 466 467 ZErrno ZBackingFile::split_and_fallocate(bool punch_hole, size_t offset, size_t length) { 468 // Try first half 469 const size_t offset0 = offset; 470 const size_t length0 = align_up(length / 2, _block_size); 471 const ZErrno err0 = fallocate(punch_hole, offset0, length0); 472 if (err0) { 473 return err0; 474 } 475 476 // Try second half 477 const size_t offset1 = offset0 + length0; 478 const size_t length1 = length - length0; 479 const ZErrno err1 = fallocate(punch_hole, offset1, length1); 480 if (err1) { 481 return err1; 482 } 483 484 // Success 485 return 0; 486 } 487 488 ZErrno ZBackingFile::fallocate(bool punch_hole, size_t offset, size_t length) { 489 assert(is_aligned(offset, _block_size), "Invalid offset"); 490 assert(is_aligned(length, _block_size), "Invalid length"); 491 492 const ZErrno err = punch_hole ? fallocate_punch_hole(offset, length) : fallocate_fill_hole(offset, length); 493 if (err == EINTR && length > _block_size) { 494 // Calling fallocate(2) with a large length can take a long time to 495 // complete. When running profilers, such as VTune, this syscall will 496 // be constantly interrupted by signals. Expanding the file in smaller 497 // steps avoids this problem. 498 return split_and_fallocate(punch_hole, offset, length); 499 } 500 501 return err; 502 } 503 504 bool ZBackingFile::commit_inner(size_t offset, size_t length) { 505 log_trace(gc, heap)("Committing memory: " SIZE_FORMAT "M-" SIZE_FORMAT "M (" SIZE_FORMAT "M)", 506 offset / M, (offset + length) / M, length / M); 507 508 retry: 509 const ZErrno err = fallocate(false /* punch_hole */, offset, length); 510 if (err) { 511 if (err == ENOSPC && !is_init_completed() && is_hugetlbfs() && z_fallocate_hugetlbfs_attempts-- > 0) { 512 // If we fail to allocate during initialization, due to lack of space on 513 // the hugetlbfs filesystem, then we wait and retry a few times before 514 // giving up. Otherwise there is a risk that running JVMs back-to-back 515 // will fail, since there is a delay between process termination and the 516 // huge pages owned by that process being returned to the huge page pool 517 // and made available for new allocations. 518 log_debug(gc, init)("Failed to commit memory (%s), retrying", err.to_string()); 519 520 // Wait and retry in one second, in the hope that huge pages will be 521 // available by then. 522 sleep(1); 523 goto retry; 524 } 525 526 // Failed 527 log_error(gc)("Failed to commit memory (%s)", err.to_string()); 528 return false; 529 } 530 531 // Success 532 return true; 533 } 534 535 size_t ZBackingFile::commit(size_t offset, size_t length) { 536 // Try to commit the whole region 537 if (commit_inner(offset, length)) { 538 // Success 539 return length; 540 } 541 542 // Failed, try to commit as much as possible 543 size_t start = offset; 544 size_t end = offset + length; 545 546 for (;;) { 547 length = align_down((end - start) / 2, ZGranuleSize); 548 if (length < ZGranuleSize) { 549 // Done, don't commit more 550 return start - offset; 551 } 552 553 if (commit_inner(start, length)) { 554 // Success, try commit more 555 start += length; 556 } else { 557 // Failed, try commit less 558 end -= length; 559 } 560 } 561 } 562 563 size_t ZBackingFile::uncommit(size_t offset, size_t length) { 564 log_trace(gc, heap)("Uncommitting memory: " SIZE_FORMAT "M-" SIZE_FORMAT "M (" SIZE_FORMAT "M)", 565 offset / M, (offset + length) / M, length / M); 566 567 const ZErrno err = fallocate(true /* punch_hole */, offset, length); 568 if (err) { 569 log_error(gc)("Failed to uncommit memory (%s)", err.to_string()); 570 return 0; 571 } 572 573 return length; 574 }