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src/hotspot/os_cpu/linux_x86/gc/z/zBackingFile_linux_x86.cpp
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*** 24,81 ****
#include "precompiled.hpp"
#include "gc/z/zArray.inline.hpp"
#include "gc/z/zBackingFile_linux_x86.hpp"
#include "gc/z/zBackingPath_linux_x86.hpp"
#include "gc/z/zErrno.hpp"
#include "gc/z/zLargePages.inline.hpp"
#include "logging/log.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>
! // 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"
!
// Support for building on older Linux systems
! #ifndef __NR_memfd_create
! #define __NR_memfd_create 319
#endif
#ifndef MFD_CLOEXEC
#define MFD_CLOEXEC 0x0001U
#endif
#ifndef MFD_HUGETLB
#define MFD_HUGETLB 0x0004U
#endif
#ifndef O_CLOEXEC
#define O_CLOEXEC 02000000
#endif
#ifndef O_TMPFILE
#define O_TMPFILE (020000000 | O_DIRECTORY)
#endif
// Filesystem types, see statfs(2)
#ifndef TMPFS_MAGIC
#define TMPFS_MAGIC 0x01021994
#endif
#ifndef HUGETLBFS_MAGIC
#define HUGETLBFS_MAGIC 0x958458f6
#endif
// Preferred tmpfs mount points, ordered by priority
static const char* z_preferred_tmpfs_mountpoints[] = {
"/dev/shm",
"/run/shm",
NULL
--- 24,103 ----
#include "precompiled.hpp"
#include "gc/z/zArray.inline.hpp"
#include "gc/z/zBackingFile_linux_x86.hpp"
#include "gc/z/zBackingPath_linux_x86.hpp"
#include "gc/z/zErrno.hpp"
+ #include "gc/z/zGlobals.hpp"
#include "gc/z/zLargePages.inline.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/syscall.h>
#include <sys/types.h>
#include <unistd.h>
! //
// Support for building on older Linux systems
! //
!
! // System calls
! #ifndef SYS_fallocate
! #define SYS_fallocate 285
#endif
+ #ifndef SYS_memfd_create
+ #define SYS_memfd_create 319
+ #endif
+
+ // 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
*** 86,154 ****
"/dev/hugepages",
"/hugepages",
NULL
};
! static int z_memfd_create(const char *name, unsigned int flags) {
! return syscall(__NR_memfd_create, name, flags);
}
! bool ZBackingFile::_hugetlbfs_mmap_retry = true;
ZBackingFile::ZBackingFile() :
_fd(-1),
_filesystem(0),
_available(0),
_initialized(false) {
// Create backing file
_fd = create_fd(ZFILENAME_HEAP);
if (_fd == -1) {
return;
}
// Get filesystem statistics
! struct statfs statfs_buf;
! if (fstatfs(_fd, &statfs_buf) == -1) {
ZErrno err;
! log_error(gc, init)("Failed to determine filesystem type for backing file (%s)",
! err.to_string());
return;
}
! _filesystem = statfs_buf.f_type;
! _available = statfs_buf.f_bavail * statfs_buf.f_bsize;
// Make sure we're on a supported filesystem
if (!is_tmpfs() && !is_hugetlbfs()) {
! log_error(gc, init)("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, init)("-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, init)("-XX:+UseTransparentHugePages on a %s filesystem not supported by kernel",
! ZFILESYSTEM_TMPFS);
return;
}
if (ZLargePages::is_explicit() && !is_hugetlbfs()) {
! log_error(gc, init)("-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, init)("-XX:+UseLargePages must be enabled when using a %s filesystem",
! ZFILESYSTEM_HUGETLBFS);
return;
}
// Successfully initialized
_initialized = true;
--- 108,190 ----
"/dev/hugepages",
"/hugepages",
NULL
};
! static int z_fallocate_hugetlbfs_attempts = 3;
! static bool z_fallocate_supported = true;
!
! static int z_fallocate(int fd, int mode, size_t offset, size_t length) {
! return syscall(SYS_fallocate, fd, mode, offset, length);
}
! static int z_memfd_create(const char *name, unsigned int flags) {
! return syscall(SYS_memfd_create, name, flags);
! }
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;
*** 163,173 ****
const int extra_flags = ZLargePages::is_explicit() ? MFD_HUGETLB : 0;
const int fd = z_memfd_create(filename, MFD_CLOEXEC | extra_flags);
if (fd == -1) {
ZErrno err;
log_debug(gc, init)("Failed to create memfd file (%s)",
! ((UseLargePages && err == EINVAL) ? "Hugepages not supported" : err.to_string()));
return -1;
}
log_info(gc, init)("Heap backed by file: /memfd:%s", filename);
--- 199,209 ----
const int extra_flags = ZLargePages::is_explicit() ? MFD_HUGETLB : 0;
const int fd = z_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);
*** 183,193 ****
: z_preferred_tmpfs_mountpoints;
// Find mountpoint
ZBackingPath path(filesystem, preferred_mountpoints);
if (path.get() == NULL) {
! log_error(gc, init)("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.
--- 219,229 ----
: 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.
*** 199,209 ****
} else {
// Get inode number for anonymous file
struct stat stat_buf;
if (fstat(fd_anon, &stat_buf) == -1) {
ZErrno err;
! log_error(gc, init)("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);
--- 235,245 ----
} 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);
*** 218,235 ****
// 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, init)("Failed to create file %s (%s)", filename, err.to_string());
return -1;
}
// Unlink file
if (unlink(filename) == -1) {
ZErrno err;
! log_error(gc, init)("Failed to unlink file %s (%s)", filename, err.to_string());
return -1;
}
log_info(gc, init)("Heap backed by file: %s", filename);
--- 254,271 ----
// 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);
*** 260,269 ****
--- 296,309 ----
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 {
*** 278,426 ****
// 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;
}
! bool ZBackingFile::try_split_and_expand_tmpfs(size_t offset, size_t length, size_t alignment) const {
! // Try first smaller part.
! const size_t offset0 = offset;
! const size_t length0 = align_up(length / 2, alignment);
! if (!try_expand_tmpfs(offset0, length0, alignment)) {
! return false;
! }
!
! // Try second smaller part.
! const size_t offset1 = offset0 + length0;
! const size_t length1 = length - length0;
! if (!try_expand_tmpfs(offset1, length1, alignment)) {
! return false;
}
! return true;
}
! bool ZBackingFile::try_expand_tmpfs(size_t offset, size_t length, size_t alignment) const {
! assert(length > 0, "Invalid length");
! assert(is_aligned(length, alignment), "Invalid length");
!
! ZErrno err = posix_fallocate(_fd, offset, length);
!
! if (err == EINTR && length > alignment) {
! // Calling posix_fallocate() 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 try_split_and_expand_tmpfs(offset, length, alignment);
}
! if (err) {
! log_error(gc)("Failed to allocate backing file (%s)", err.to_string());
! return false;
}
! return true;
}
! bool ZBackingFile::try_expand_tmpfs(size_t offset, size_t length) const {
! assert(is_tmpfs(), "Wrong filesystem");
! return try_expand_tmpfs(offset, length, os::vm_page_size());
}
! bool ZBackingFile::try_expand_hugetlbfs(size_t offset, size_t length) const {
! assert(is_hugetlbfs(), "Wrong filesystem");
!
! // Prior to kernel 4.3, hugetlbfs did not support posix_fallocate().
! // Instead of posix_fallocate() we can use a well-known workaround,
! // which involves truncating the file to requested size and then try
! // to map it to verify that there are enough huge pages available to
! // back it.
! while (ftruncate(_fd, offset + length) == -1) {
! ZErrno err;
! if (err != EINTR) {
! log_error(gc)("Failed to truncate backing file (%s)", err.to_string());
! return false;
}
}
! // If we fail mapping during initialization, i.e. when we are pre-mapping
! // the heap, 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.
! void* addr = MAP_FAILED;
! const int max_attempts = 5;
! for (int attempt = 1; attempt <= max_attempts; attempt++) {
! addr = mmap(0, length, PROT_READ|PROT_WRITE, MAP_SHARED, _fd, offset);
! if (addr != MAP_FAILED || !_hugetlbfs_mmap_retry) {
! // Mapping was successful or mmap retry is disabled
! break;
}
! ZErrno err;
! log_debug(gc)("Failed to map backing file (%s), attempt %d of %d",
! err.to_string(), attempt, max_attempts);
! // Wait and retry in one second, in the hope that
! // huge pages will be available by then.
! sleep(1);
}
! // Disable mmap retry from now on
! if (_hugetlbfs_mmap_retry) {
! _hugetlbfs_mmap_retry = false;
}
! if (addr == MAP_FAILED) {
! // Not enough huge pages left
! ZErrno err;
! log_error(gc)("Failed to map backing file (%s)", err.to_string());
! return false;
}
! // Successful mapping, unmap again. From now on the pages we mapped
! // will be reserved for this file.
! if (munmap(addr, length) == -1) {
! ZErrno err;
! log_error(gc)("Failed to unmap backing file (%s)", err.to_string());
! return false;
}
! return true;
}
! bool ZBackingFile::try_expand_tmpfs_or_hugetlbfs(size_t offset, size_t length, size_t alignment) const {
! assert(is_aligned(offset, alignment), "Invalid offset");
! assert(is_aligned(length, alignment), "Invalid length");
! log_debug(gc)("Expanding heap from " SIZE_FORMAT "M to " SIZE_FORMAT "M", offset / M, (offset + length) / M);
! return is_hugetlbfs() ? try_expand_hugetlbfs(offset, length) : try_expand_tmpfs(offset, length);
}
! size_t ZBackingFile::try_expand(size_t offset, size_t length, size_t alignment) const {
! size_t start = offset;
! size_t end = offset + length;
! // Try to expand
! if (try_expand_tmpfs_or_hugetlbfs(start, length, alignment)) {
// Success
! return end;
}
! // Failed, try to expand as much as possible
for (;;) {
! length = align_down((end - start) / 2, alignment);
! if (length < alignment) {
! // Done, don't expand more
! return start;
}
! if (try_expand_tmpfs_or_hugetlbfs(start, length, alignment)) {
! // Success, try expand more
start += length;
} else {
! // Failed, try expand less
end -= length;
}
}
}
--- 318,590 ----
// 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 = z_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 (z_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;
+ }
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