--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/os/linux/gc/z/zBackingFile_linux.cpp Wed Aug 28 09:50:21 2019 +0200
@@ -0,0 +1,574 @@
+/*
+ * Copyright (c) 2015, 2019, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+#include "precompiled.hpp"
+#include "gc/z/zArray.inline.hpp"
+#include "gc/z/zBackingFile_linux.hpp"
+#include "gc/z/zBackingPath_linux.hpp"
+#include "gc/z/zErrno.hpp"
+#include "gc/z/zGlobals.hpp"
+#include "gc/z/zLargePages.inline.hpp"
+#include "gc/z/zSyscall_linux.hpp"
+#include "logging/log.hpp"
+#include "runtime/init.hpp"
+#include "runtime/os.hpp"
+#include "utilities/align.hpp"
+#include "utilities/debug.hpp"
+
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/statfs.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+//
+// Support for building on older Linux systems
+//
+
+// memfd_create(2) flags
+#ifndef MFD_CLOEXEC
+#define MFD_CLOEXEC 0x0001U
+#endif
+#ifndef MFD_HUGETLB
+#define MFD_HUGETLB 0x0004U
+#endif
+
+// open(2) flags
+#ifndef O_CLOEXEC
+#define O_CLOEXEC 02000000
+#endif
+#ifndef O_TMPFILE
+#define O_TMPFILE (020000000 | O_DIRECTORY)
+#endif
+
+// fallocate(2) flags
+#ifndef FALLOC_FL_KEEP_SIZE
+#define FALLOC_FL_KEEP_SIZE 0x01
+#endif
+#ifndef FALLOC_FL_PUNCH_HOLE
+#define FALLOC_FL_PUNCH_HOLE 0x02
+#endif
+
+// Filesystem types, see statfs(2)
+#ifndef TMPFS_MAGIC
+#define TMPFS_MAGIC 0x01021994
+#endif
+#ifndef HUGETLBFS_MAGIC
+#define HUGETLBFS_MAGIC 0x958458f6
+#endif
+
+// Filesystem names
+#define ZFILESYSTEM_TMPFS "tmpfs"
+#define ZFILESYSTEM_HUGETLBFS "hugetlbfs"
+
+// Sysfs file for transparent huge page on tmpfs
+#define ZFILENAME_SHMEM_ENABLED "/sys/kernel/mm/transparent_hugepage/shmem_enabled"
+
+// Java heap filename
+#define ZFILENAME_HEAP "java_heap"
+
+// Preferred tmpfs mount points, ordered by priority
+static const char* z_preferred_tmpfs_mountpoints[] = {
+ "/dev/shm",
+ "/run/shm",
+ NULL
+};
+
+// Preferred hugetlbfs mount points, ordered by priority
+static const char* z_preferred_hugetlbfs_mountpoints[] = {
+ "/dev/hugepages",
+ "/hugepages",
+ NULL
+};
+
+static int z_fallocate_hugetlbfs_attempts = 3;
+static bool z_fallocate_supported = true;
+
+ZBackingFile::ZBackingFile() :
+ _fd(-1),
+ _size(0),
+ _filesystem(0),
+ _block_size(0),
+ _available(0),
+ _initialized(false) {
+
+ // Create backing file
+ _fd = create_fd(ZFILENAME_HEAP);
+ if (_fd == -1) {
+ return;
+ }
+
+ // Get filesystem statistics
+ struct statfs buf;
+ if (fstatfs(_fd, &buf) == -1) {
+ ZErrno err;
+ log_error(gc)("Failed to determine filesystem type for backing file (%s)", err.to_string());
+ return;
+ }
+
+ _filesystem = buf.f_type;
+ _block_size = buf.f_bsize;
+ _available = buf.f_bavail * _block_size;
+
+ // Make sure we're on a supported filesystem
+ if (!is_tmpfs() && !is_hugetlbfs()) {
+ log_error(gc)("Backing file must be located on a %s or a %s filesystem",
+ ZFILESYSTEM_TMPFS, ZFILESYSTEM_HUGETLBFS);
+ return;
+ }
+
+ // Make sure the filesystem type matches requested large page type
+ if (ZLargePages::is_transparent() && !is_tmpfs()) {
+ log_error(gc)("-XX:+UseTransparentHugePages can only be enable when using a %s filesystem",
+ ZFILESYSTEM_TMPFS);
+ return;
+ }
+
+ if (ZLargePages::is_transparent() && !tmpfs_supports_transparent_huge_pages()) {
+ log_error(gc)("-XX:+UseTransparentHugePages on a %s filesystem not supported by kernel",
+ ZFILESYSTEM_TMPFS);
+ return;
+ }
+
+ if (ZLargePages::is_explicit() && !is_hugetlbfs()) {
+ log_error(gc)("-XX:+UseLargePages (without -XX:+UseTransparentHugePages) can only be enabled "
+ "when using a %s filesystem", ZFILESYSTEM_HUGETLBFS);
+ return;
+ }
+
+ if (!ZLargePages::is_explicit() && is_hugetlbfs()) {
+ log_error(gc)("-XX:+UseLargePages must be enabled when using a %s filesystem",
+ ZFILESYSTEM_HUGETLBFS);
+ return;
+ }
+
+ const size_t expected_block_size = is_tmpfs() ? os::vm_page_size() : os::large_page_size();
+ if (expected_block_size != _block_size) {
+ log_error(gc)("%s filesystem has unexpected block size " SIZE_FORMAT " (expected " SIZE_FORMAT ")",
+ is_tmpfs() ? ZFILESYSTEM_TMPFS : ZFILESYSTEM_HUGETLBFS, _block_size, expected_block_size);
+ return;
+ }
+
+ // Successfully initialized
+ _initialized = true;
+}
+
+int ZBackingFile::create_mem_fd(const char* name) const {
+ // Create file name
+ char filename[PATH_MAX];
+ snprintf(filename, sizeof(filename), "%s%s", name, ZLargePages::is_explicit() ? ".hugetlb" : "");
+
+ // Create file
+ const int extra_flags = ZLargePages::is_explicit() ? MFD_HUGETLB : 0;
+ const int fd = ZSyscall::memfd_create(filename, MFD_CLOEXEC | extra_flags);
+ if (fd == -1) {
+ ZErrno err;
+ log_debug(gc, init)("Failed to create memfd file (%s)",
+ ((ZLargePages::is_explicit() && err == EINVAL) ? "Hugepages not supported" : err.to_string()));
+ return -1;
+ }
+
+ log_info(gc, init)("Heap backed by file: /memfd:%s", filename);
+
+ return fd;
+}
+
+int ZBackingFile::create_file_fd(const char* name) const {
+ const char* const filesystem = ZLargePages::is_explicit()
+ ? ZFILESYSTEM_HUGETLBFS
+ : ZFILESYSTEM_TMPFS;
+ const char** const preferred_mountpoints = ZLargePages::is_explicit()
+ ? z_preferred_hugetlbfs_mountpoints
+ : z_preferred_tmpfs_mountpoints;
+
+ // Find mountpoint
+ ZBackingPath path(filesystem, preferred_mountpoints);
+ if (path.get() == NULL) {
+ log_error(gc)("Use -XX:ZPath to specify the path to a %s filesystem", filesystem);
+ return -1;
+ }
+
+ // Try to create an anonymous file using the O_TMPFILE flag. Note that this
+ // flag requires kernel >= 3.11. If this fails we fall back to open/unlink.
+ const int fd_anon = os::open(path.get(), O_TMPFILE|O_EXCL|O_RDWR|O_CLOEXEC, S_IRUSR|S_IWUSR);
+ if (fd_anon == -1) {
+ ZErrno err;
+ log_debug(gc, init)("Failed to create anonymous file in %s (%s)", path.get(),
+ (err == EINVAL ? "Not supported" : err.to_string()));
+ } else {
+ // Get inode number for anonymous file
+ struct stat stat_buf;
+ if (fstat(fd_anon, &stat_buf) == -1) {
+ ZErrno err;
+ log_error(gc)("Failed to determine inode number for anonymous file (%s)", err.to_string());
+ return -1;
+ }
+
+ log_info(gc, init)("Heap backed by file: %s/#" UINT64_FORMAT, path.get(), (uint64_t)stat_buf.st_ino);
+
+ return fd_anon;
+ }
+
+ log_debug(gc, init)("Falling back to open/unlink");
+
+ // Create file name
+ char filename[PATH_MAX];
+ snprintf(filename, sizeof(filename), "%s/%s.%d", path.get(), name, os::current_process_id());
+
+ // Create file
+ const int fd = os::open(filename, O_CREAT|O_EXCL|O_RDWR|O_CLOEXEC, S_IRUSR|S_IWUSR);
+ if (fd == -1) {
+ ZErrno err;
+ log_error(gc)("Failed to create file %s (%s)", filename, err.to_string());
+ return -1;
+ }
+
+ // Unlink file
+ if (unlink(filename) == -1) {
+ ZErrno err;
+ log_error(gc)("Failed to unlink file %s (%s)", filename, err.to_string());
+ return -1;
+ }
+
+ log_info(gc, init)("Heap backed by file: %s", filename);
+
+ return fd;
+}
+
+int ZBackingFile::create_fd(const char* name) const {
+ if (ZPath == NULL) {
+ // If the path is not explicitly specified, then we first try to create a memfd file
+ // instead of looking for a tmpfd/hugetlbfs mount point. Note that memfd_create() might
+ // not be supported at all (requires kernel >= 3.17), or it might not support large
+ // pages (requires kernel >= 4.14). If memfd_create() fails, then we try to create a
+ // file on an accessible tmpfs or hugetlbfs mount point.
+ const int fd = create_mem_fd(name);
+ if (fd != -1) {
+ return fd;
+ }
+
+ log_debug(gc, init)("Falling back to searching for an accessible mount point");
+ }
+
+ return create_file_fd(name);
+}
+
+bool ZBackingFile::is_initialized() const {
+ return _initialized;
+}
+
+int ZBackingFile::fd() const {
+ return _fd;
+}
+
+size_t ZBackingFile::size() const {
+ return _size;
+}
+
+size_t ZBackingFile::available() const {
+ return _available;
+}
+
+bool ZBackingFile::is_tmpfs() const {
+ return _filesystem == TMPFS_MAGIC;
+}
+
+bool ZBackingFile::is_hugetlbfs() const {
+ return _filesystem == HUGETLBFS_MAGIC;
+}
+
+bool ZBackingFile::tmpfs_supports_transparent_huge_pages() const {
+ // If the shmem_enabled file exists and is readable then we
+ // know the kernel supports transparent huge pages for tmpfs.
+ return access(ZFILENAME_SHMEM_ENABLED, R_OK) == 0;
+}
+
+ZErrno ZBackingFile::fallocate_compat_ftruncate(size_t size) const {
+ while (ftruncate(_fd, size) == -1) {
+ if (errno != EINTR) {
+ // Failed
+ return errno;
+ }
+ }
+
+ // Success
+ return 0;
+}
+
+ZErrno ZBackingFile::fallocate_compat_mmap(size_t offset, size_t length, bool touch) const {
+ // On hugetlbfs, mapping a file segment will fail immediately, without
+ // the need to touch the mapped pages first, if there aren't enough huge
+ // pages available to back the mapping.
+ void* const addr = mmap(0, length, PROT_READ|PROT_WRITE, MAP_SHARED, _fd, offset);
+ if (addr == MAP_FAILED) {
+ // Failed
+ return errno;
+ }
+
+ // Once mapped, the huge pages are only reserved. We need to touch them
+ // to associate them with the file segment. Note that we can not punch
+ // hole in file segments which only have reserved pages.
+ if (touch) {
+ char* const start = (char*)addr;
+ char* const end = start + length;
+ os::pretouch_memory(start, end, _block_size);
+ }
+
+ // Unmap again. From now on, the huge pages that were mapped are allocated
+ // to this file. There's no risk in getting SIGBUS when touching them.
+ if (munmap(addr, length) == -1) {
+ // Failed
+ return errno;
+ }
+
+ // Success
+ return 0;
+}
+
+ZErrno ZBackingFile::fallocate_compat_pwrite(size_t offset, size_t length) const {
+ uint8_t data = 0;
+
+ // Allocate backing memory by writing to each block
+ for (size_t pos = offset; pos < offset + length; pos += _block_size) {
+ if (pwrite(_fd, &data, sizeof(data), pos) == -1) {
+ // Failed
+ return errno;
+ }
+ }
+
+ // Success
+ return 0;
+}
+
+ZErrno ZBackingFile::fallocate_fill_hole_compat(size_t offset, size_t length) {
+ // fallocate(2) is only supported by tmpfs since Linux 3.5, and by hugetlbfs
+ // since Linux 4.3. When fallocate(2) is not supported we emulate it using
+ // ftruncate/pwrite (for tmpfs) or ftruncate/mmap/munmap (for hugetlbfs).
+
+ const size_t end = offset + length;
+ if (end > _size) {
+ // Increase file size
+ const ZErrno err = fallocate_compat_ftruncate(end);
+ if (err) {
+ // Failed
+ return err;
+ }
+ }
+
+ // Allocate backing memory
+ const ZErrno err = is_hugetlbfs() ? fallocate_compat_mmap(offset, length, false /* touch */)
+ : fallocate_compat_pwrite(offset, length);
+ if (err) {
+ if (end > _size) {
+ // Restore file size
+ fallocate_compat_ftruncate(_size);
+ }
+
+ // Failed
+ return err;
+ }
+
+ if (end > _size) {
+ // Record new file size
+ _size = end;
+ }
+
+ // Success
+ return 0;
+}
+
+ZErrno ZBackingFile::fallocate_fill_hole_syscall(size_t offset, size_t length) {
+ const int mode = 0; // Allocate
+ const int res = ZSyscall::fallocate(_fd, mode, offset, length);
+ if (res == -1) {
+ // Failed
+ return errno;
+ }
+
+ const size_t end = offset + length;
+ if (end > _size) {
+ // Record new file size
+ _size = end;
+ }
+
+ // Success
+ return 0;
+}
+
+ZErrno ZBackingFile::fallocate_fill_hole(size_t offset, size_t length) {
+ // Using compat mode is more efficient when allocating space on hugetlbfs.
+ // Note that allocating huge pages this way will only reserve them, and not
+ // associate them with segments of the file. We must guarantee that we at
+ // some point touch these segments, otherwise we can not punch hole in them.
+ if (z_fallocate_supported && !is_hugetlbfs()) {
+ const ZErrno err = fallocate_fill_hole_syscall(offset, length);
+ if (!err) {
+ // Success
+ return 0;
+ }
+
+ if (err != ENOSYS && err != EOPNOTSUPP) {
+ // Failed
+ return err;
+ }
+
+ // Not supported
+ log_debug(gc)("Falling back to fallocate() compatibility mode");
+ z_fallocate_supported = false;
+ }
+
+ return fallocate_fill_hole_compat(offset, length);
+}
+
+ZErrno ZBackingFile::fallocate_punch_hole(size_t offset, size_t length) {
+ if (is_hugetlbfs()) {
+ // We can only punch hole in pages that have been touched. Non-touched
+ // pages are only reserved, and not associated with any specific file
+ // segment. We don't know which pages have been previously touched, so
+ // we always touch them here to guarantee that we can punch hole.
+ const ZErrno err = fallocate_compat_mmap(offset, length, true /* touch */);
+ if (err) {
+ // Failed
+ return err;
+ }
+ }
+
+ const int mode = FALLOC_FL_PUNCH_HOLE|FALLOC_FL_KEEP_SIZE;
+ if (ZSyscall::fallocate(_fd, mode, offset, length) == -1) {
+ // Failed
+ return errno;
+ }
+
+ // Success
+ return 0;
+}
+
+ZErrno ZBackingFile::split_and_fallocate(bool punch_hole, size_t offset, size_t length) {
+ // Try first half
+ const size_t offset0 = offset;
+ const size_t length0 = align_up(length / 2, _block_size);
+ const ZErrno err0 = fallocate(punch_hole, offset0, length0);
+ if (err0) {
+ return err0;
+ }
+
+ // Try second half
+ const size_t offset1 = offset0 + length0;
+ const size_t length1 = length - length0;
+ const ZErrno err1 = fallocate(punch_hole, offset1, length1);
+ if (err1) {
+ return err1;
+ }
+
+ // Success
+ return 0;
+}
+
+ZErrno ZBackingFile::fallocate(bool punch_hole, size_t offset, size_t length) {
+ assert(is_aligned(offset, _block_size), "Invalid offset");
+ assert(is_aligned(length, _block_size), "Invalid length");
+
+ const ZErrno err = punch_hole ? fallocate_punch_hole(offset, length) : fallocate_fill_hole(offset, length);
+ if (err == EINTR && length > _block_size) {
+ // Calling fallocate(2) with a large length can take a long time to
+ // complete. When running profilers, such as VTune, this syscall will
+ // be constantly interrupted by signals. Expanding the file in smaller
+ // steps avoids this problem.
+ return split_and_fallocate(punch_hole, offset, length);
+ }
+
+ return err;
+}
+
+bool ZBackingFile::commit_inner(size_t offset, size_t length) {
+ log_trace(gc, heap)("Committing memory: " SIZE_FORMAT "M-" SIZE_FORMAT "M (" SIZE_FORMAT "M)",
+ offset / M, (offset + length) / M, length / M);
+
+retry:
+ const ZErrno err = fallocate(false /* punch_hole */, offset, length);
+ if (err) {
+ if (err == ENOSPC && !is_init_completed() && is_hugetlbfs() && z_fallocate_hugetlbfs_attempts-- > 0) {
+ // If we fail to allocate during initialization, due to lack of space on
+ // the hugetlbfs filesystem, then we wait and retry a few times before
+ // giving up. Otherwise there is a risk that running JVMs back-to-back
+ // will fail, since there is a delay between process termination and the
+ // huge pages owned by that process being returned to the huge page pool
+ // and made available for new allocations.
+ log_debug(gc, init)("Failed to commit memory (%s), retrying", err.to_string());
+
+ // Wait and retry in one second, in the hope that huge pages will be
+ // available by then.
+ sleep(1);
+ goto retry;
+ }
+
+ // Failed
+ log_error(gc)("Failed to commit memory (%s)", err.to_string());
+ return false;
+ }
+
+ // Success
+ return true;
+}
+
+size_t ZBackingFile::commit(size_t offset, size_t length) {
+ // Try to commit the whole region
+ if (commit_inner(offset, length)) {
+ // Success
+ return length;
+ }
+
+ // Failed, try to commit as much as possible
+ size_t start = offset;
+ size_t end = offset + length;
+
+ for (;;) {
+ length = align_down((end - start) / 2, ZGranuleSize);
+ if (length < ZGranuleSize) {
+ // Done, don't commit more
+ return start - offset;
+ }
+
+ if (commit_inner(start, length)) {
+ // Success, try commit more
+ start += length;
+ } else {
+ // Failed, try commit less
+ end -= length;
+ }
+ }
+}
+
+size_t ZBackingFile::uncommit(size_t offset, size_t length) {
+ log_trace(gc, heap)("Uncommitting memory: " SIZE_FORMAT "M-" SIZE_FORMAT "M (" SIZE_FORMAT "M)",
+ offset / M, (offset + length) / M, length / M);
+
+ const ZErrno err = fallocate(true /* punch_hole */, offset, length);
+ if (err) {
+ log_error(gc)("Failed to uncommit memory (%s)", err.to_string());
+ return 0;
+ }
+
+ return length;
+}