--- a/src/hotspot/os/bsd/gc/z/zBackingFile_bsd.cpp	Thu Jan 16 17:37:09 2020 -0800
+++ b/src/hotspot/os/bsd/gc/z/zBackingFile_bsd.cpp	Fri Jan 17 10:20:37 2020 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2019, 2020, 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
@@ -89,6 +89,10 @@
   return _initialized;
 }
 
+void ZBackingFile::warn_commit_limits(size_t max) const {
+  // Does nothing
+}
+
 size_t ZBackingFile::size() const {
   return _size;
 }

--- a/src/hotspot/os/bsd/gc/z/zBackingFile_bsd.hpp	Thu Jan 16 17:37:09 2020 -0800
+++ b/src/hotspot/os/bsd/gc/z/zBackingFile_bsd.hpp	Fri Jan 17 10:20:37 2020 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2019, 2020, 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
@@ -47,6 +47,8 @@
 
   bool is_initialized() const;
 
+  void warn_commit_limits(size_t max) const;
+
   size_t size() const;
 
   size_t commit(size_t offset, size_t length);

--- a/src/hotspot/os/bsd/gc/z/zPhysicalMemoryBacking_bsd.cpp	Thu Jan 16 17:37:09 2020 -0800
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,219 +0,0 @@
-/*
- * Copyright (c) 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/zAddress.inline.hpp"
-#include "gc/z/zGlobals.hpp"
-#include "gc/z/zLargePages.inline.hpp"
-#include "gc/z/zPhysicalMemory.inline.hpp"
-#include "gc/z/zPhysicalMemoryBacking_bsd.hpp"
-#include "runtime/globals.hpp"
-#include "runtime/init.hpp"
-#include "runtime/os.hpp"
-#include "utilities/align.hpp"
-#include "utilities/debug.hpp"
-
-bool ZPhysicalMemoryBacking::is_initialized() const {
-  return _file.is_initialized();
-}
-
-void ZPhysicalMemoryBacking::warn_commit_limits(size_t max) const {
-  // Does nothing
-}
-
-bool ZPhysicalMemoryBacking::supports_uncommit() {
-  assert(!is_init_completed(), "Invalid state");
-  assert(_file.size() >= ZGranuleSize, "Invalid size");
-
-  // Test if uncommit is supported by uncommitting and then re-committing a granule
-  return commit(uncommit(ZGranuleSize)) == ZGranuleSize;
-}
-
-size_t ZPhysicalMemoryBacking::commit(size_t size) {
-  size_t committed = 0;
-
-  // Fill holes in the backing file
-  while (committed < size) {
-    size_t allocated = 0;
-    const size_t remaining = size - committed;
-    const uintptr_t start = _uncommitted.alloc_from_front_at_most(remaining, &allocated);
-    if (start == UINTPTR_MAX) {
-      // No holes to commit
-      break;
-    }
-
-    // Try commit hole
-    const size_t filled = _file.commit(start, allocated);
-    if (filled > 0) {
-      // Successful or partialy successful
-      _committed.free(start, filled);
-      committed += filled;
-    }
-    if (filled < allocated) {
-      // Failed or partialy failed
-      _uncommitted.free(start + filled, allocated - filled);
-      return committed;
-    }
-  }
-
-  // Expand backing file
-  if (committed < size) {
-    const size_t remaining = size - committed;
-    const uintptr_t start = _file.size();
-    const size_t expanded = _file.commit(start, remaining);
-    if (expanded > 0) {
-      // Successful or partialy successful
-      _committed.free(start, expanded);
-      committed += expanded;
-    }
-  }
-
-  return committed;
-}
-
-size_t ZPhysicalMemoryBacking::uncommit(size_t size) {
-  size_t uncommitted = 0;
-
-  // Punch holes in backing file
-  while (uncommitted < size) {
-    size_t allocated = 0;
-    const size_t remaining = size - uncommitted;
-    const uintptr_t start = _committed.alloc_from_back_at_most(remaining, &allocated);
-    assert(start != UINTPTR_MAX, "Allocation should never fail");
-
-    // Try punch hole
-    const size_t punched = _file.uncommit(start, allocated);
-    if (punched > 0) {
-      // Successful or partialy successful
-      _uncommitted.free(start, punched);
-      uncommitted += punched;
-    }
-    if (punched < allocated) {
-      // Failed or partialy failed
-      _committed.free(start + punched, allocated - punched);
-      return uncommitted;
-    }
-  }
-
-  return uncommitted;
-}
-
-ZPhysicalMemory ZPhysicalMemoryBacking::alloc(size_t size) {
-  assert(is_aligned(size, ZGranuleSize), "Invalid size");
-
-  ZPhysicalMemory pmem;
-
-  // Allocate segments
-  for (size_t allocated = 0; allocated < size; allocated += ZGranuleSize) {
-    const uintptr_t start = _committed.alloc_from_front(ZGranuleSize);
-    assert(start != UINTPTR_MAX, "Allocation should never fail");
-    pmem.add_segment(ZPhysicalMemorySegment(start, ZGranuleSize));
-  }
-
-  return pmem;
-}
-
-void ZPhysicalMemoryBacking::free(const ZPhysicalMemory& pmem) {
-  const size_t nsegments = pmem.nsegments();
-
-  // Free segments
-  for (size_t i = 0; i < nsegments; i++) {
-    const ZPhysicalMemorySegment& segment = pmem.segment(i);
-    _committed.free(segment.start(), segment.size());
-  }
-}
-
-void ZPhysicalMemoryBacking::pretouch_view(uintptr_t addr, size_t size) const {
-  const size_t page_size = ZLargePages::is_explicit() ? ZGranuleSize : os::vm_page_size();
-  os::pretouch_memory((void*)addr, (void*)(addr + size), page_size);
-}
-
-void ZPhysicalMemoryBacking::map_view(const ZPhysicalMemory& pmem, uintptr_t addr) const {
-  const size_t nsegments = pmem.nsegments();
-  size_t size = 0;
-
-  // Map segments
-  for (size_t i = 0; i < nsegments; i++) {
-    const ZPhysicalMemorySegment& segment = pmem.segment(i);
-    const uintptr_t segment_addr = addr + size;
-    _file.map(segment_addr, segment.size(), segment.start());
-    size += segment.size();
-  }
-}
-
-void ZPhysicalMemoryBacking::unmap_view(const ZPhysicalMemory& pmem, uintptr_t addr) const {
-  _file.unmap(addr, pmem.size());
-}
-
-uintptr_t ZPhysicalMemoryBacking::nmt_address(uintptr_t offset) const {
-  // From an NMT point of view we treat the first heap view (marked0) as committed
-  return ZAddress::marked0(offset);
-}
-
-void ZPhysicalMemoryBacking::pretouch(uintptr_t offset, size_t size) const {
-  if (ZVerifyViews) {
-    // Pre-touch good view
-    pretouch_view(ZAddress::good(offset), size);
-  } else {
-    // Pre-touch all views
-    pretouch_view(ZAddress::marked0(offset), size);
-    pretouch_view(ZAddress::marked1(offset), size);
-    pretouch_view(ZAddress::remapped(offset), size);
-  }
-}
-
-void ZPhysicalMemoryBacking::map(const ZPhysicalMemory& pmem, uintptr_t offset) const {
-  if (ZVerifyViews) {
-    // Map good view
-    map_view(pmem, ZAddress::good(offset));
-  } else {
-    // Map all views
-    map_view(pmem, ZAddress::marked0(offset));
-    map_view(pmem, ZAddress::marked1(offset));
-    map_view(pmem, ZAddress::remapped(offset));
-  }
-}
-
-void ZPhysicalMemoryBacking::unmap(const ZPhysicalMemory& pmem, uintptr_t offset) const {
-  if (ZVerifyViews) {
-    // Unmap good view
-    unmap_view(pmem, ZAddress::good(offset));
-  } else {
-    // Unmap all views
-    unmap_view(pmem, ZAddress::marked0(offset));
-    unmap_view(pmem, ZAddress::marked1(offset));
-    unmap_view(pmem, ZAddress::remapped(offset));
-  }
-}
-
-void ZPhysicalMemoryBacking::debug_map(const ZPhysicalMemory& pmem, uintptr_t offset) const {
-  // Map good view
-  assert(ZVerifyViews, "Should be enabled");
-  map_view(pmem, ZAddress::good(offset));
-}
-
-void ZPhysicalMemoryBacking::debug_unmap(const ZPhysicalMemory& pmem, uintptr_t offset) const {
-  // Unmap good view
-  assert(ZVerifyViews, "Should be enabled");
-  unmap_view(pmem, ZAddress::good(offset));
-}

--- a/src/hotspot/os/bsd/gc/z/zPhysicalMemoryBacking_bsd.hpp	Thu Jan 16 17:37:09 2020 -0800
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,65 +0,0 @@
-/*
- * Copyright (c) 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.
- */
-
-#ifndef OS_BSD_GC_Z_ZPHYSICALMEMORYBACKING_BSD_HPP
-#define OS_BSD_GC_Z_ZPHYSICALMEMORYBACKING_BSD_HPP
-
-#include "gc/z/zBackingFile_bsd.hpp"
-#include "gc/z/zMemory.hpp"
-
-class ZPhysicalMemory;
-
-class ZPhysicalMemoryBacking {
-private:
-  ZBackingFile   _file;
-  ZMemoryManager _committed;
-  ZMemoryManager _uncommitted;
-
-  void pretouch_view(uintptr_t addr, size_t size) const;
-  void map_view(const ZPhysicalMemory& pmem, uintptr_t addr) const;
-  void unmap_view(const ZPhysicalMemory& pmem, uintptr_t addr) const;
-
-public:
-  bool is_initialized() const;
-
-  void warn_commit_limits(size_t max) const;
-  bool supports_uncommit();
-
-  size_t commit(size_t size);
-  size_t uncommit(size_t size);
-
-  ZPhysicalMemory alloc(size_t size);
-  void free(const ZPhysicalMemory& pmem);
-
-  uintptr_t nmt_address(uintptr_t offset) const;
-
-  void pretouch(uintptr_t offset, size_t size) const;
-
-  void map(const ZPhysicalMemory& pmem, uintptr_t offset) const;
-  void unmap(const ZPhysicalMemory& pmem, uintptr_t offset) const;
-
-  void debug_map(const ZPhysicalMemory& pmem, uintptr_t offset) const;
-  void debug_unmap(const ZPhysicalMemory& pmem, uintptr_t offset) const;
-};
-
-#endif // OS_BSD_GC_Z_ZPHYSICALMEMORYBACKING_BSD_HPP

--- a/src/hotspot/os/linux/gc/z/zBackingFile_linux.cpp	Thu Jan 16 17:37:09 2020 -0800
+++ b/src/hotspot/os/linux/gc/z/zBackingFile_linux.cpp	Fri Jan 17 10:20:37 2020 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 2020, 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
@@ -36,6 +36,7 @@
 #include "utilities/debug.hpp"
 
 #include <fcntl.h>
+#include <stdio.h>
 #include <sys/mman.h>
 #include <sys/stat.h>
 #include <sys/statfs.h>
@@ -82,6 +83,9 @@
 #define ZFILESYSTEM_TMPFS                "tmpfs"
 #define ZFILESYSTEM_HUGETLBFS            "hugetlbfs"
 
+// Proc file entry for max map mount
+#define ZFILENAME_PROC_MAX_MAP_COUNT     "/proc/sys/vm/max_map_count"
+
 // Sysfs file for transparent huge page on tmpfs
 #define ZFILENAME_SHMEM_ENABLED          "/sys/kernel/mm/transparent_hugepage/shmem_enabled"
 
@@ -278,18 +282,78 @@
   return _initialized;
 }
 
-int ZBackingFile::fd() const {
-  return _fd;
+void ZBackingFile::warn_available_space(size_t max) const {
+  // Note that the available space on a tmpfs or a hugetlbfs filesystem
+  // will be zero if no size limit was specified when it was mounted.
+  if (_available == 0) {
+    // No size limit set, skip check
+    log_info(gc, init)("Available space on backing filesystem: N/A");
+    return;
+  }
+
+  log_info(gc, init)("Available space on backing filesystem: " SIZE_FORMAT "M", _available / M);
+
+  // Warn if the filesystem doesn't currently have enough space available to hold
+  // the max heap size. The max heap size will be capped if we later hit this limit
+  // when trying to expand the heap.
+  if (_available < max) {
+    log_warning(gc)("***** WARNING! INCORRECT SYSTEM CONFIGURATION DETECTED! *****");
+    log_warning(gc)("Not enough space available on the backing filesystem to hold the current max Java heap");
+    log_warning(gc)("size (" SIZE_FORMAT "M). Please adjust the size of the backing filesystem accordingly "
+                    "(available", max / M);
+    log_warning(gc)("space is currently " SIZE_FORMAT "M). Continuing execution with the current filesystem "
+                    "size could", _available / M);
+    log_warning(gc)("lead to a premature OutOfMemoryError being thrown, due to failure to map memory.");
+  }
+}
+
+void ZBackingFile::warn_max_map_count(size_t max) const {
+  const char* const filename = ZFILENAME_PROC_MAX_MAP_COUNT;
+  FILE* const file = fopen(filename, "r");
+  if (file == NULL) {
+    // Failed to open file, skip check
+    log_debug(gc, init)("Failed to open %s", filename);
+    return;
+  }
+
+  size_t actual_max_map_count = 0;
+  const int result = fscanf(file, SIZE_FORMAT, &actual_max_map_count);
+  fclose(file);
+  if (result != 1) {
+    // Failed to read file, skip check
+    log_debug(gc, init)("Failed to read %s", filename);
+    return;
+  }
+
+  // The required max map count is impossible to calculate exactly since subsystems
+  // other than ZGC are also creating memory mappings, and we have no control over that.
+  // However, ZGC tends to create the most mappings and dominate the total count.
+  // In the worst cases, ZGC will map each granule three times, i.e. once per heap view.
+  // We speculate that we need another 20% to allow for non-ZGC subsystems to map memory.
+  const size_t required_max_map_count = (max / ZGranuleSize) * 3 * 1.2;
+  if (actual_max_map_count < required_max_map_count) {
+    log_warning(gc)("***** WARNING! INCORRECT SYSTEM CONFIGURATION DETECTED! *****");
+    log_warning(gc)("The system limit on number of memory mappings per process might be too low for the given");
+    log_warning(gc)("max Java heap size (" SIZE_FORMAT "M). Please adjust %s to allow for at",
+                    max / M, filename);
+    log_warning(gc)("least " SIZE_FORMAT " mappings (current limit is " SIZE_FORMAT "). Continuing execution "
+                    "with the current", required_max_map_count, actual_max_map_count);
+    log_warning(gc)("limit could lead to a fatal error, due to failure to map memory.");
+  }
+}
+
+void ZBackingFile::warn_commit_limits(size_t max) const {
+  // Warn if available space is too low
+  warn_available_space(max);
+
+  // Warn if max map count is too low
+  warn_max_map_count(max);
 }
 
 size_t ZBackingFile::size() const {
   return _size;
 }
 
-size_t ZBackingFile::available() const {
-  return _available;
-}
-
 bool ZBackingFile::is_tmpfs() const {
   return _filesystem == TMPFS_MAGIC;
 }
@@ -572,3 +636,22 @@
 
   return length;
 }
+
+void ZBackingFile::map(uintptr_t addr, size_t size, uintptr_t offset) const {
+  const void* const res = mmap((void*)addr, size, PROT_READ|PROT_WRITE, MAP_FIXED|MAP_SHARED, _fd, offset);
+  if (res == MAP_FAILED) {
+    ZErrno err;
+    fatal("Failed to map memory (%s)", err.to_string());
+  }
+}
+
+void ZBackingFile::unmap(uintptr_t addr, size_t size) const {
+  // Note that we must keep the address space reservation intact and just detach
+  // the backing memory. For this reason we map a new anonymous, non-accessible
+  // and non-reserved page over the mapping instead of actually unmapping.
+  const void* const res = mmap((void*)addr, size, PROT_NONE, MAP_FIXED | MAP_ANONYMOUS | MAP_PRIVATE | MAP_NORESERVE, -1, 0);
+  if (res == MAP_FAILED) {
+    ZErrno err;
+    fatal("Failed to map memory (%s)", err.to_string());
+  }
+}

--- a/src/hotspot/os/linux/gc/z/zBackingFile_linux.hpp	Thu Jan 16 17:37:09 2020 -0800
+++ b/src/hotspot/os/linux/gc/z/zBackingFile_linux.hpp	Fri Jan 17 10:20:37 2020 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 2020, 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
@@ -37,6 +37,9 @@
   size_t   _available;
   bool     _initialized;
 
+  void warn_available_space(size_t max) const;
+  void warn_max_map_count(size_t max) const;
+
   int create_mem_fd(const char* name) const;
   int create_file_fd(const char* name) const;
   int create_fd(const char* name) const;
@@ -62,12 +65,15 @@
 
   bool is_initialized() const;
 
-  int fd() const;
+  void warn_commit_limits(size_t max) const;
+
   size_t size() const;
-  size_t available() const;
 
   size_t commit(size_t offset, size_t length);
   size_t uncommit(size_t offset, size_t length);
+
+  void map(uintptr_t addr, size_t size, uintptr_t offset) const;
+  void unmap(uintptr_t addr, size_t size) const;
 };
 
 #endif // OS_LINUX_GC_Z_ZBACKINGFILE_LINUX_HPP

--- a/src/hotspot/os/linux/gc/z/zPhysicalMemoryBacking_linux.cpp	Thu Jan 16 17:37:09 2020 -0800
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,340 +0,0 @@
-/*
- * 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/zAddress.inline.hpp"
-#include "gc/z/zErrno.hpp"
-#include "gc/z/zGlobals.hpp"
-#include "gc/z/zLargePages.inline.hpp"
-#include "gc/z/zMemory.hpp"
-#include "gc/z/zNUMA.hpp"
-#include "gc/z/zPhysicalMemory.inline.hpp"
-#include "gc/z/zPhysicalMemoryBacking_linux.hpp"
-#include "logging/log.hpp"
-#include "runtime/globals.hpp"
-#include "runtime/init.hpp"
-#include "runtime/os.hpp"
-#include "utilities/align.hpp"
-#include "utilities/debug.hpp"
-
-#include <stdio.h>
-#include <sys/mman.h>
-#include <sys/types.h>
-
-//
-// Support for building on older Linux systems
-//
-
-// madvise(2) flags
-#ifndef MADV_HUGEPAGE
-#define MADV_HUGEPAGE                        14
-#endif
-
-// Proc file entry for max map mount
-#define ZFILENAME_PROC_MAX_MAP_COUNT         "/proc/sys/vm/max_map_count"
-
-bool ZPhysicalMemoryBacking::is_initialized() const {
-  return _file.is_initialized();
-}
-
-void ZPhysicalMemoryBacking::warn_available_space(size_t max) const {
-  // Note that the available space on a tmpfs or a hugetlbfs filesystem
-  // will be zero if no size limit was specified when it was mounted.
-  const size_t available = _file.available();
-  if (available == 0) {
-    // No size limit set, skip check
-    log_info(gc, init)("Available space on backing filesystem: N/A");
-    return;
-  }
-
-  log_info(gc, init)("Available space on backing filesystem: " SIZE_FORMAT "M", available / M);
-
-  // Warn if the filesystem doesn't currently have enough space available to hold
-  // the max heap size. The max heap size will be capped if we later hit this limit
-  // when trying to expand the heap.
-  if (available < max) {
-    log_warning(gc)("***** WARNING! INCORRECT SYSTEM CONFIGURATION DETECTED! *****");
-    log_warning(gc)("Not enough space available on the backing filesystem to hold the current max Java heap");
-    log_warning(gc)("size (" SIZE_FORMAT "M). Please adjust the size of the backing filesystem accordingly "
-                    "(available", max / M);
-    log_warning(gc)("space is currently " SIZE_FORMAT "M). Continuing execution with the current filesystem "
-                    "size could", available / M);
-    log_warning(gc)("lead to a premature OutOfMemoryError being thrown, due to failure to map memory.");
-  }
-}
-
-void ZPhysicalMemoryBacking::warn_max_map_count(size_t max) const {
-  const char* const filename = ZFILENAME_PROC_MAX_MAP_COUNT;
-  FILE* const file = fopen(filename, "r");
-  if (file == NULL) {
-    // Failed to open file, skip check
-    log_debug(gc, init)("Failed to open %s", filename);
-    return;
-  }
-
-  size_t actual_max_map_count = 0;
-  const int result = fscanf(file, SIZE_FORMAT, &actual_max_map_count);
-  fclose(file);
-  if (result != 1) {
-    // Failed to read file, skip check
-    log_debug(gc, init)("Failed to read %s", filename);
-    return;
-  }
-
-  // The required max map count is impossible to calculate exactly since subsystems
-  // other than ZGC are also creating memory mappings, and we have no control over that.
-  // However, ZGC tends to create the most mappings and dominate the total count.
-  // In the worst cases, ZGC will map each granule three times, i.e. once per heap view.
-  // We speculate that we need another 20% to allow for non-ZGC subsystems to map memory.
-  const size_t required_max_map_count = (max / ZGranuleSize) * 3 * 1.2;
-  if (actual_max_map_count < required_max_map_count) {
-    log_warning(gc)("***** WARNING! INCORRECT SYSTEM CONFIGURATION DETECTED! *****");
-    log_warning(gc)("The system limit on number of memory mappings per process might be too low for the given");
-    log_warning(gc)("max Java heap size (" SIZE_FORMAT "M). Please adjust %s to allow for at",
-                    max / M, filename);
-    log_warning(gc)("least " SIZE_FORMAT " mappings (current limit is " SIZE_FORMAT "). Continuing execution "
-                    "with the current", required_max_map_count, actual_max_map_count);
-    log_warning(gc)("limit could lead to a fatal error, due to failure to map memory.");
-  }
-}
-
-void ZPhysicalMemoryBacking::warn_commit_limits(size_t max) const {
-  // Warn if available space is too low
-  warn_available_space(max);
-
-  // Warn if max map count is too low
-  warn_max_map_count(max);
-}
-
-bool ZPhysicalMemoryBacking::supports_uncommit() {
-  assert(!is_init_completed(), "Invalid state");
-  assert(_file.size() >= ZGranuleSize, "Invalid size");
-
-  // Test if uncommit is supported by uncommitting and then re-committing a granule
-  return commit(uncommit(ZGranuleSize)) == ZGranuleSize;
-}
-
-size_t ZPhysicalMemoryBacking::commit(size_t size) {
-  size_t committed = 0;
-
-  // Fill holes in the backing file
-  while (committed < size) {
-    size_t allocated = 0;
-    const size_t remaining = size - committed;
-    const uintptr_t start = _uncommitted.alloc_from_front_at_most(remaining, &allocated);
-    if (start == UINTPTR_MAX) {
-      // No holes to commit
-      break;
-    }
-
-    // Try commit hole
-    const size_t filled = _file.commit(start, allocated);
-    if (filled > 0) {
-      // Successful or partialy successful
-      _committed.free(start, filled);
-      committed += filled;
-    }
-    if (filled < allocated) {
-      // Failed or partialy failed
-      _uncommitted.free(start + filled, allocated - filled);
-      return committed;
-    }
-  }
-
-  // Expand backing file
-  if (committed < size) {
-    const size_t remaining = size - committed;
-    const uintptr_t start = _file.size();
-    const size_t expanded = _file.commit(start, remaining);
-    if (expanded > 0) {
-      // Successful or partialy successful
-      _committed.free(start, expanded);
-      committed += expanded;
-    }
-  }
-
-  return committed;
-}
-
-size_t ZPhysicalMemoryBacking::uncommit(size_t size) {
-  size_t uncommitted = 0;
-
-  // Punch holes in backing file
-  while (uncommitted < size) {
-    size_t allocated = 0;
-    const size_t remaining = size - uncommitted;
-    const uintptr_t start = _committed.alloc_from_back_at_most(remaining, &allocated);
-    assert(start != UINTPTR_MAX, "Allocation should never fail");
-
-    // Try punch hole
-    const size_t punched = _file.uncommit(start, allocated);
-    if (punched > 0) {
-      // Successful or partialy successful
-      _uncommitted.free(start, punched);
-      uncommitted += punched;
-    }
-    if (punched < allocated) {
-      // Failed or partialy failed
-      _committed.free(start + punched, allocated - punched);
-      return uncommitted;
-    }
-  }
-
-  return uncommitted;
-}
-
-ZPhysicalMemory ZPhysicalMemoryBacking::alloc(size_t size) {
-  assert(is_aligned(size, ZGranuleSize), "Invalid size");
-
-  ZPhysicalMemory pmem;
-
-  // Allocate segments
-  for (size_t allocated = 0; allocated < size; allocated += ZGranuleSize) {
-    const uintptr_t start = _committed.alloc_from_front(ZGranuleSize);
-    assert(start != UINTPTR_MAX, "Allocation should never fail");
-    pmem.add_segment(ZPhysicalMemorySegment(start, ZGranuleSize));
-  }
-
-  return pmem;
-}
-
-void ZPhysicalMemoryBacking::free(const ZPhysicalMemory& pmem) {
-  const size_t nsegments = pmem.nsegments();
-
-  // Free segments
-  for (size_t i = 0; i < nsegments; i++) {
-    const ZPhysicalMemorySegment& segment = pmem.segment(i);
-    _committed.free(segment.start(), segment.size());
-  }
-}
-
-void ZPhysicalMemoryBacking::map_failed(ZErrno err) const {
-  if (err == ENOMEM) {
-    fatal("Failed to map memory. Please check the system limit on number of "
-          "memory mappings allowed per process (see %s)", ZFILENAME_PROC_MAX_MAP_COUNT);
-  } else {
-    fatal("Failed to map memory (%s)", err.to_string());
-  }
-}
-
-void ZPhysicalMemoryBacking::advise_view(uintptr_t addr, size_t size, int advice) const {
-  if (madvise((void*)addr, size, advice) == -1) {
-    ZErrno err;
-    log_error(gc)("Failed to advise on memory (advice %d, %s)", advice, err.to_string());
-  }
-}
-
-void ZPhysicalMemoryBacking::pretouch_view(uintptr_t addr, size_t size) const {
-  const size_t page_size = ZLargePages::is_explicit() ? os::large_page_size() : os::vm_page_size();
-  os::pretouch_memory((void*)addr, (void*)(addr + size), page_size);
-}
-
-void ZPhysicalMemoryBacking::map_view(const ZPhysicalMemory& pmem, uintptr_t addr) const {
-  const size_t nsegments = pmem.nsegments();
-  size_t size = 0;
-
-  // Map segments
-  for (size_t i = 0; i < nsegments; i++) {
-    const ZPhysicalMemorySegment& segment = pmem.segment(i);
-    const uintptr_t segment_addr = addr + size;
-    const void* const res = mmap((void*)segment_addr, segment.size(), PROT_READ|PROT_WRITE, MAP_FIXED|MAP_SHARED, _file.fd(), segment.start());
-    if (res == MAP_FAILED) {
-      ZErrno err;
-      map_failed(err);
-    }
-
-    size += segment.size();
-  }
-
-  // Advise on use of transparent huge pages before touching it
-  if (ZLargePages::is_transparent()) {
-    advise_view(addr, size, MADV_HUGEPAGE);
-  }
-
-  // NUMA interleave memory before touching it
-  ZNUMA::memory_interleave(addr, size);
-}
-
-void ZPhysicalMemoryBacking::unmap_view(const ZPhysicalMemory& pmem, uintptr_t addr) const {
-  // Note that we must keep the address space reservation intact and just detach
-  // the backing memory. For this reason we map a new anonymous, non-accessible
-  // and non-reserved page over the mapping instead of actually unmapping.
-  const void* const res = mmap((void*)addr, pmem.size(), PROT_NONE, MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE|MAP_NORESERVE, -1, 0);
-  if (res == MAP_FAILED) {
-    ZErrno err;
-    map_failed(err);
-  }
-}
-
-uintptr_t ZPhysicalMemoryBacking::nmt_address(uintptr_t offset) const {
-  // From an NMT point of view we treat the first heap view (marked0) as committed
-  return ZAddress::marked0(offset);
-}
-
-void ZPhysicalMemoryBacking::pretouch(uintptr_t offset, size_t size) const {
-  if (ZVerifyViews) {
-    // Pre-touch good view
-    pretouch_view(ZAddress::good(offset), size);
-  } else {
-    // Pre-touch all views
-    pretouch_view(ZAddress::marked0(offset), size);
-    pretouch_view(ZAddress::marked1(offset), size);
-    pretouch_view(ZAddress::remapped(offset), size);
-  }
-}
-
-void ZPhysicalMemoryBacking::map(const ZPhysicalMemory& pmem, uintptr_t offset) const {
-  if (ZVerifyViews) {
-    // Map good view
-    map_view(pmem, ZAddress::good(offset));
-  } else {
-    // Map all views
-    map_view(pmem, ZAddress::marked0(offset));
-    map_view(pmem, ZAddress::marked1(offset));
-    map_view(pmem, ZAddress::remapped(offset));
-  }
-}
-
-void ZPhysicalMemoryBacking::unmap(const ZPhysicalMemory& pmem, uintptr_t offset) const {
-  if (ZVerifyViews) {
-    // Unmap good view
-    unmap_view(pmem, ZAddress::good(offset));
-  } else {
-    // Unmap all views
-    unmap_view(pmem, ZAddress::marked0(offset));
-    unmap_view(pmem, ZAddress::marked1(offset));
-    unmap_view(pmem, ZAddress::remapped(offset));
-  }
-}
-
-void ZPhysicalMemoryBacking::debug_map(const ZPhysicalMemory& pmem, uintptr_t offset) const {
-  // Map good view
-  assert(ZVerifyViews, "Should be enabled");
-  map_view(pmem, ZAddress::good(offset));
-}
-
-void ZPhysicalMemoryBacking::debug_unmap(const ZPhysicalMemory& pmem, uintptr_t offset) const {
-  // Unmap good view
-  assert(ZVerifyViews, "Should be enabled");
-  unmap_view(pmem, ZAddress::good(offset));
-}

--- a/src/hotspot/os/linux/gc/z/zPhysicalMemoryBacking_linux.hpp	Thu Jan 16 17:37:09 2020 -0800
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,72 +0,0 @@
-/*
- * 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.
- */
-
-#ifndef OS_LINUX_GC_Z_ZPHYSICALMEMORYBACKING_LINUX_HPP
-#define OS_LINUX_GC_Z_ZPHYSICALMEMORYBACKING_LINUX_HPP
-
-#include "gc/z/zBackingFile_linux.hpp"
-#include "gc/z/zMemory.hpp"
-
-class ZErrno;
-class ZPhysicalMemory;
-
-class ZPhysicalMemoryBacking {
-private:
-  ZBackingFile   _file;
-  ZMemoryManager _committed;
-  ZMemoryManager _uncommitted;
-
-  void warn_available_space(size_t max) const;
-  void warn_max_map_count(size_t max) const;
-
-  void map_failed(ZErrno err) const;
-
-  void advise_view(uintptr_t addr, size_t size, int advice) const;
-  void pretouch_view(uintptr_t addr, size_t size) const;
-  void map_view(const ZPhysicalMemory& pmem, uintptr_t addr) const;
-  void unmap_view(const ZPhysicalMemory& pmem, uintptr_t addr) const;
-
-public:
-  bool is_initialized() const;
-
-  void warn_commit_limits(size_t max) const;
-  bool supports_uncommit();
-
-  size_t commit(size_t size);
-  size_t uncommit(size_t size);
-
-  ZPhysicalMemory alloc(size_t size);
-  void free(const ZPhysicalMemory& pmem);
-
-  uintptr_t nmt_address(uintptr_t offset) const;
-
-  void pretouch(uintptr_t offset, size_t size) const;
-
-  void map(const ZPhysicalMemory& pmem, uintptr_t offset) const;
-  void unmap(const ZPhysicalMemory& pmem, uintptr_t offset) const;
-
-  void debug_map(const ZPhysicalMemory& pmem, uintptr_t offset) const;
-  void debug_unmap(const ZPhysicalMemory& pmem, uintptr_t offset) const;
-};
-
-#endif // OS_LINUX_GC_Z_ZPHYSICALMEMORYBACKING_LINUX_HPP

--- a/src/hotspot/os/windows/gc/z/zBackingFile_windows.cpp	Thu Jan 16 17:37:09 2020 -0800
+++ b/src/hotspot/os/windows/gc/z/zBackingFile_windows.cpp	Fri Jan 17 10:20:37 2020 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2019, 2020, 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
@@ -39,6 +39,14 @@
     _handles(MaxHeapSize),
     _size(0) {}
 
+bool ZBackingFile::is_initialized() const {
+  return true;
+}
+
+void ZBackingFile::warn_commit_limits(size_t max) const {
+  // Does nothing
+}
+
 size_t ZBackingFile::size() const {
   return _size;
 }

--- a/src/hotspot/os/windows/gc/z/zBackingFile_windows.hpp	Thu Jan 16 17:37:09 2020 -0800
+++ b/src/hotspot/os/windows/gc/z/zBackingFile_windows.hpp	Fri Jan 17 10:20:37 2020 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2019, 2020, 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
@@ -44,6 +44,10 @@
 public:
   ZBackingFile();
 
+  bool is_initialized() const;
+
+  void warn_commit_limits(size_t max) const;
+
   size_t size() const;
 
   size_t commit(size_t offset, size_t length);

--- a/src/hotspot/os/windows/gc/z/zPhysicalMemoryBacking_windows.cpp	Thu Jan 16 17:37:09 2020 -0800
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,219 +0,0 @@
-/*
- * Copyright (c) 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/zAddress.inline.hpp"
-#include "gc/z/zGlobals.hpp"
-#include "gc/z/zLargePages.inline.hpp"
-#include "gc/z/zMapper_windows.hpp"
-#include "gc/z/zPhysicalMemory.inline.hpp"
-#include "gc/z/zPhysicalMemoryBacking_windows.hpp"
-#include "runtime/globals.hpp"
-#include "runtime/init.hpp"
-#include "runtime/os.hpp"
-#include "utilities/align.hpp"
-#include "utilities/debug.hpp"
-
-bool ZPhysicalMemoryBacking::is_initialized() const {
-  return true;
-}
-
-void ZPhysicalMemoryBacking::warn_commit_limits(size_t max) const {
-  // Does nothing
-}
-
-bool ZPhysicalMemoryBacking::supports_uncommit() {
-  assert(!is_init_completed(), "Invalid state");
-  assert(_file.size() >= ZGranuleSize, "Invalid size");
-
-  // Test if uncommit is supported by uncommitting and then re-committing a granule
-  return commit(uncommit(ZGranuleSize)) == ZGranuleSize;
-}
-
-size_t ZPhysicalMemoryBacking::commit(size_t size) {
-  size_t committed = 0;
-
-  // Fill holes in the backing file
-  while (committed < size) {
-    size_t allocated = 0;
-    const size_t remaining = size - committed;
-    const uintptr_t start = _uncommitted.alloc_from_front_at_most(remaining, &allocated);
-    if (start == UINTPTR_MAX) {
-      // No holes to commit
-      break;
-    }
-
-    // Try commit hole
-    const size_t filled = _file.commit(start, allocated);
-    if (filled > 0) {
-      // Successful or partialy successful
-      _committed.free(start, filled);
-      committed += filled;
-    }
-    if (filled < allocated) {
-      // Failed or partialy failed
-      _uncommitted.free(start + filled, allocated - filled);
-      return committed;
-    }
-  }
-
-  // Expand backing file
-  if (committed < size) {
-    const size_t remaining = size - committed;
-    const uintptr_t start = _file.size();
-    const size_t expanded = _file.commit(start, remaining);
-    if (expanded > 0) {
-      // Successful or partialy successful
-      _committed.free(start, expanded);
-      committed += expanded;
-    }
-  }
-
-  return committed;
-}
-
-size_t ZPhysicalMemoryBacking::uncommit(size_t size) {
-  size_t uncommitted = 0;
-
-  // Punch holes in backing file
-  while (uncommitted < size) {
-    size_t allocated = 0;
-    const size_t remaining = size - uncommitted;
-    const uintptr_t start = _committed.alloc_from_back_at_most(remaining, &allocated);
-    assert(start != UINTPTR_MAX, "Allocation should never fail");
-
-    // Try punch hole
-    const size_t punched = _file.uncommit(start, allocated);
-    if (punched > 0) {
-      // Successful or partialy successful
-      _uncommitted.free(start, punched);
-      uncommitted += punched;
-    }
-    if (punched < allocated) {
-      // Failed or partialy failed
-      _committed.free(start + punched, allocated - punched);
-      return uncommitted;
-    }
-  }
-
-  return uncommitted;
-}
-
-ZPhysicalMemory ZPhysicalMemoryBacking::alloc(size_t size) {
-  assert(is_aligned(size, ZGranuleSize), "Invalid size");
-
-  ZPhysicalMemory pmem;
-
-  // Allocate segments
-  for (size_t allocated = 0; allocated < size; allocated += ZGranuleSize) {
-    const uintptr_t start = _committed.alloc_from_front(ZGranuleSize);
-    assert(start != UINTPTR_MAX, "Allocation should never fail");
-    pmem.add_segment(ZPhysicalMemorySegment(start, ZGranuleSize));
-  }
-
-  return pmem;
-}
-
-void ZPhysicalMemoryBacking::free(const ZPhysicalMemory& pmem) {
-  const size_t nsegments = pmem.nsegments();
-
-  // Free segments
-  for (size_t i = 0; i < nsegments; i++) {
-    const ZPhysicalMemorySegment& segment = pmem.segment(i);
-    _committed.free(segment.start(), segment.size());
-  }
-}
-
-void ZPhysicalMemoryBacking::pretouch_view(uintptr_t addr, size_t size) const {
-  const size_t page_size = ZLargePages::is_explicit() ? os::large_page_size() : os::vm_page_size();
-  os::pretouch_memory((void*)addr, (void*)(addr + size), page_size);
-}
-
-void ZPhysicalMemoryBacking::map_view(const ZPhysicalMemory& pmem, uintptr_t addr) const {
-  const size_t nsegments = pmem.nsegments();
-  size_t size = 0;
-
-  // Map segments
-  for (size_t i = 0; i < nsegments; i++) {
-    const ZPhysicalMemorySegment& segment = pmem.segment(i);
-    _file.map(addr + size, segment.size(), segment.start());
-    size += segment.size();
-  }
-}
-
-void ZPhysicalMemoryBacking::unmap_view(const ZPhysicalMemory& pmem, uintptr_t addr) const {
-  _file.unmap(addr, pmem.size());
-}
-
-uintptr_t ZPhysicalMemoryBacking::nmt_address(uintptr_t offset) const {
-  // From an NMT point of view we treat the first heap view (marked0) as committed
-  return ZAddress::marked0(offset);
-}
-
-void ZPhysicalMemoryBacking::pretouch(uintptr_t offset, size_t size) const {
-  if (ZVerifyViews) {
-    // Pre-touch good view
-    pretouch_view(ZAddress::good(offset), size);
-  } else {
-    // Pre-touch all views
-    pretouch_view(ZAddress::marked0(offset), size);
-    pretouch_view(ZAddress::marked1(offset), size);
-    pretouch_view(ZAddress::remapped(offset), size);
-  }
-}
-
-void ZPhysicalMemoryBacking::map(const ZPhysicalMemory& pmem, uintptr_t offset) const {
-  if (ZVerifyViews) {
-    // Map good view
-    map_view(pmem, ZAddress::good(offset));
-  } else {
-    // Map all views
-    map_view(pmem, ZAddress::marked0(offset));
-    map_view(pmem, ZAddress::marked1(offset));
-    map_view(pmem, ZAddress::remapped(offset));
-  }
-}
-
-void ZPhysicalMemoryBacking::unmap(const ZPhysicalMemory& pmem, uintptr_t offset) const {
-  if (ZVerifyViews) {
-    // Unmap good view
-    unmap_view(pmem, ZAddress::good(offset));
-  } else {
-    // Unmap all views
-    unmap_view(pmem, ZAddress::marked0(offset));
-    unmap_view(pmem, ZAddress::marked1(offset));
-    unmap_view(pmem, ZAddress::remapped(offset));
-  }
-}
-
-void ZPhysicalMemoryBacking::debug_map(const ZPhysicalMemory& pmem, uintptr_t offset) const {
-  // Map good view
-  assert(ZVerifyViews, "Should be enabled");
-  map_view(pmem, ZAddress::good(offset));
-}
-
-void ZPhysicalMemoryBacking::debug_unmap(const ZPhysicalMemory& pmem, uintptr_t offset) const {
-  // Unmap good view
-  assert(ZVerifyViews, "Should be enabled");
-  unmap_view(pmem, ZAddress::good(offset));
-}

--- a/src/hotspot/os/windows/gc/z/zPhysicalMemoryBacking_windows.hpp	Thu Jan 16 17:37:09 2020 -0800
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,65 +0,0 @@
-/*
- * Copyright (c) 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.
- */
-
-#ifndef OS_WINDOWS_GC_Z_ZPHYSICALMEMORYBACKING_WINDOWS_HPP
-#define OS_WINDOWS_GC_Z_ZPHYSICALMEMORYBACKING_WINDOWS_HPP
-
-#include "gc/z/zBackingFile_windows.hpp"
-#include "gc/z/zMemory.hpp"
-
-class ZPhysicalMemory;
-
-class ZPhysicalMemoryBacking {
-private:
-  ZBackingFile   _file;
-  ZMemoryManager _committed;
-  ZMemoryManager _uncommitted;
-
-  void pretouch_view(uintptr_t addr, size_t size) const;
-  void map_view(const ZPhysicalMemory& pmem, uintptr_t addr) const;
-  void unmap_view(const ZPhysicalMemory& pmem, uintptr_t addr) const;
-
-public:
-  bool is_initialized() const;
-
-  void warn_commit_limits(size_t max) const;
-  bool supports_uncommit();
-
-  size_t commit(size_t size);
-  size_t uncommit(size_t size);
-
-  ZPhysicalMemory alloc(size_t size);
-  void free(const ZPhysicalMemory& pmem);
-
-  uintptr_t nmt_address(uintptr_t offset) const;
-
-  void pretouch(uintptr_t offset, size_t size) const;
-
-  void map(const ZPhysicalMemory& pmem, uintptr_t offset) const;
-  void unmap(const ZPhysicalMemory& pmem, uintptr_t offset) const;
-
-  void debug_map(const ZPhysicalMemory& pmem, uintptr_t offset) const;
-  void debug_unmap(const ZPhysicalMemory& pmem, uintptr_t offset) const;
-};
-
-#endif // OS_WINDOWS_GC_Z_ZPHYSICALMEMORYBACKING_WINDOWS_HPP

--- a/src/hotspot/share/gc/z/zNUMA.cpp	Thu Jan 16 17:37:09 2020 -0800
+++ b/src/hotspot/share/gc/z/zNUMA.cpp	Fri Jan 17 10:20:37 2020 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016, 2017, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2016, 2020, 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
@@ -32,24 +32,11 @@
   initialize_platform();
 
   log_info(gc, init)("NUMA Support: %s", to_string());
-  if (is_enabled()) {
+  if (_enabled) {
     log_info(gc, init)("NUMA Nodes: %u", count());
   }
 }
 
-bool ZNUMA::is_enabled() {
-  return _enabled;
-}
-
-void ZNUMA::memory_interleave(uintptr_t addr, size_t size) {
-  if (!_enabled) {
-    // NUMA support not enabled
-    return;
-  }
-
-  os::numa_make_global((char*)addr, size);
-}
-
 const char* ZNUMA::to_string() {
   return _enabled ? "Enabled" : "Disabled";
 }

--- a/src/hotspot/share/gc/z/zNUMA.hpp	Thu Jan 16 17:37:09 2020 -0800
+++ b/src/hotspot/share/gc/z/zNUMA.hpp	Fri Jan 17 10:20:37 2020 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016, 2017, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2016, 2020, 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
@@ -40,7 +40,6 @@
   static uint32_t id();
 
   static uint32_t memory_id(uintptr_t addr);
-  static void memory_interleave(uintptr_t addr, size_t size);
 
   static const char* to_string();
 };

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/z/zNUMA.inline.hpp	Fri Jan 17 10:20:37 2020 +0100
@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2019, 2020, 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.
+ */
+
+#ifndef SHARE_GC_Z_ZNUMA_INLINE_HPP
+#define SHARE_GC_Z_ZNUMA_INLINE_HPP
+
+#include "gc/z/zNUMA.hpp"
+
+inline bool ZNUMA::is_enabled() {
+  return _enabled;
+}
+
+#endif // SHARE_GC_Z_ZNUMA_INLINE_HPP

--- a/src/hotspot/share/gc/z/zPhysicalMemory.cpp	Thu Jan 16 17:37:09 2020 -0800
+++ b/src/hotspot/share/gc/z/zPhysicalMemory.cpp	Fri Jan 17 10:20:37 2020 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 2020, 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
@@ -22,10 +22,15 @@
  */
 
 #include "precompiled.hpp"
+#include "gc/z/zAddress.inline.hpp"
+#include "gc/z/zGlobals.hpp"
+#include "gc/z/zLargePages.inline.hpp"
+#include "gc/z/zNUMA.inline.hpp"
 #include "gc/z/zPhysicalMemory.inline.hpp"
-#include "logging/log.hpp"
-#include "memory/allocation.inline.hpp"
+#include "runtime/init.hpp"
+#include "runtime/os.hpp"
 #include "services/memTracker.hpp"
+#include "utilities/align.hpp"
 #include "utilities/debug.hpp"
 #include "utilities/globalDefinitions.hpp"
 
@@ -139,18 +144,23 @@
 }
 
 bool ZPhysicalMemoryManager::supports_uncommit() {
-  return _backing.supports_uncommit();
+  assert(!is_init_completed(), "Invalid state");
+  assert(_backing.size() >= ZGranuleSize, "Invalid size");
+
+  // Test if uncommit is supported by uncommitting and then re-committing a granule
+  return commit(uncommit(ZGranuleSize)) == ZGranuleSize;
 }
 
 void ZPhysicalMemoryManager::nmt_commit(const ZPhysicalMemory& pmem, uintptr_t offset) const {
-  const uintptr_t addr = _backing.nmt_address(offset);
+  // From an NMT point of view we treat the first heap view (marked0) as committed
+  const uintptr_t addr = ZAddress::marked0(offset);
   const size_t size = pmem.size();
   MemTracker::record_virtual_memory_commit((void*)addr, size, CALLER_PC);
 }
 
 void ZPhysicalMemoryManager::nmt_uncommit(const ZPhysicalMemory& pmem, uintptr_t offset) const {
   if (MemTracker::tracking_level() > NMT_minimal) {
-    const uintptr_t addr = _backing.nmt_address(offset);
+    const uintptr_t addr = ZAddress::marked0(offset);
     const size_t size = pmem.size();
     Tracker tracker(Tracker::uncommit);
     tracker.record((address)addr, size);
@@ -158,39 +168,178 @@
 }
 
 size_t ZPhysicalMemoryManager::commit(size_t size) {
-  return _backing.commit(size);
+  size_t committed = 0;
+
+  // Fill holes in the backing memory
+  while (committed < size) {
+    size_t allocated = 0;
+    const size_t remaining = size - committed;
+    const uintptr_t start = _uncommitted.alloc_from_front_at_most(remaining, &allocated);
+    if (start == UINTPTR_MAX) {
+      // No holes to commit
+      break;
+    }
+
+    // Try commit hole
+    const size_t filled = _backing.commit(start, allocated);
+    if (filled > 0) {
+      // Successful or partialy successful
+      _committed.free(start, filled);
+      committed += filled;
+    }
+    if (filled < allocated) {
+      // Failed or partialy failed
+      _uncommitted.free(start + filled, allocated - filled);
+      return committed;
+    }
+  }
+
+  // Expand backing memory
+  if (committed < size) {
+    const size_t remaining = size - committed;
+    const uintptr_t start = _backing.size();
+    const size_t expanded = _backing.commit(start, remaining);
+    if (expanded > 0) {
+      // Successful or partialy successful
+      _committed.free(start, expanded);
+      committed += expanded;
+    }
+  }
+
+  return committed;
 }
 
 size_t ZPhysicalMemoryManager::uncommit(size_t size) {
-  return _backing.uncommit(size);
+  size_t uncommitted = 0;
+
+  // Punch holes in backing memory
+  while (uncommitted < size) {
+    size_t allocated = 0;
+    const size_t remaining = size - uncommitted;
+    const uintptr_t start = _committed.alloc_from_back_at_most(remaining, &allocated);
+    assert(start != UINTPTR_MAX, "Allocation should never fail");
+
+    // Try punch hole
+    const size_t punched = _backing.uncommit(start, allocated);
+    if (punched > 0) {
+      // Successful or partialy successful
+      _uncommitted.free(start, punched);
+      uncommitted += punched;
+    }
+    if (punched < allocated) {
+      // Failed or partialy failed
+      _committed.free(start + punched, allocated - punched);
+      return uncommitted;
+    }
+  }
+
+  return uncommitted;
 }
 
 ZPhysicalMemory ZPhysicalMemoryManager::alloc(size_t size) {
-  return _backing.alloc(size);
+  assert(is_aligned(size, ZGranuleSize), "Invalid size");
+
+  ZPhysicalMemory pmem;
+
+  // Allocate segments
+  for (size_t allocated = 0; allocated < size; allocated += ZGranuleSize) {
+    const uintptr_t start = _committed.alloc_from_front(ZGranuleSize);
+    assert(start != UINTPTR_MAX, "Allocation should never fail");
+    pmem.add_segment(ZPhysicalMemorySegment(start, ZGranuleSize));
+  }
+
+  return pmem;
 }
 
 void ZPhysicalMemoryManager::free(const ZPhysicalMemory& pmem) {
-  _backing.free(pmem);
+  const size_t nsegments = pmem.nsegments();
+
+  // Free segments
+  for (size_t i = 0; i < nsegments; i++) {
+    const ZPhysicalMemorySegment& segment = pmem.segment(i);
+    _committed.free(segment.start(), segment.size());
+  }
+}
+
+void ZPhysicalMemoryManager::pretouch_view(uintptr_t addr, size_t size) const {
+  const size_t page_size = ZLargePages::is_explicit() ? ZGranuleSize : os::vm_page_size();
+  os::pretouch_memory((void*)addr, (void*)(addr + size), page_size);
+}
+
+void ZPhysicalMemoryManager::map_view(const ZPhysicalMemory& pmem, uintptr_t addr) const {
+  const size_t nsegments = pmem.nsegments();
+  size_t size = 0;
+
+  // Map segments
+  for (size_t i = 0; i < nsegments; i++) {
+    const ZPhysicalMemorySegment& segment = pmem.segment(i);
+    _backing.map(addr + size, segment.size(), segment.start());
+    size += segment.size();
+  }
+
+  // Setup NUMA interleaving
+  if (ZNUMA::is_enabled()) {
+    os::numa_make_global((char*)addr, size);
+  }
+
+  // Setup transparent large pages
+  if (ZLargePages::is_transparent()) {
+    os::realign_memory((char*)addr, size, os::large_page_size());
+  }
+}
+
+void ZPhysicalMemoryManager::unmap_view(const ZPhysicalMemory& pmem, uintptr_t addr) const {
+  _backing.unmap(addr, pmem.size());
 }
 
 void ZPhysicalMemoryManager::pretouch(uintptr_t offset, size_t size) const {
-  _backing.pretouch(offset, size);
+  if (ZVerifyViews) {
+    // Pre-touch good view
+    pretouch_view(ZAddress::good(offset), size);
+  } else {
+    // Pre-touch all views
+    pretouch_view(ZAddress::marked0(offset), size);
+    pretouch_view(ZAddress::marked1(offset), size);
+    pretouch_view(ZAddress::remapped(offset), size);
+  }
 }
 
 void ZPhysicalMemoryManager::map(const ZPhysicalMemory& pmem, uintptr_t offset) const {
-  _backing.map(pmem, offset);
+  if (ZVerifyViews) {
+    // Map good view
+    map_view(pmem, ZAddress::good(offset));
+  } else {
+    // Map all views
+    map_view(pmem, ZAddress::marked0(offset));
+    map_view(pmem, ZAddress::marked1(offset));
+    map_view(pmem, ZAddress::remapped(offset));
+  }
+
   nmt_commit(pmem, offset);
 }
 
 void ZPhysicalMemoryManager::unmap(const ZPhysicalMemory& pmem, uintptr_t offset) const {
   nmt_uncommit(pmem, offset);
-  _backing.unmap(pmem, offset);
+
+  if (ZVerifyViews) {
+    // Unmap good view
+    unmap_view(pmem, ZAddress::good(offset));
+  } else {
+    // Unmap all views
+    unmap_view(pmem, ZAddress::marked0(offset));
+    unmap_view(pmem, ZAddress::marked1(offset));
+    unmap_view(pmem, ZAddress::remapped(offset));
+  }
 }
 
 void ZPhysicalMemoryManager::debug_map(const ZPhysicalMemory& pmem, uintptr_t offset) const {
-  _backing.debug_map(pmem, offset);
+  // Map good view
+  assert(ZVerifyViews, "Should be enabled");
+  map_view(pmem, ZAddress::good(offset));
 }
 
 void ZPhysicalMemoryManager::debug_unmap(const ZPhysicalMemory& pmem, uintptr_t offset) const {
-  _backing.debug_unmap(pmem, offset);
+  // Unmap good view
+  assert(ZVerifyViews, "Should be enabled");
+  unmap_view(pmem, ZAddress::good(offset));
 }

--- a/src/hotspot/share/gc/z/zPhysicalMemory.hpp	Thu Jan 16 17:37:09 2020 -0800
+++ b/src/hotspot/share/gc/z/zPhysicalMemory.hpp	Fri Jan 17 10:20:37 2020 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 2020, 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
@@ -24,8 +24,9 @@
 #ifndef SHARE_GC_Z_ZPHYSICALMEMORY_HPP
 #define SHARE_GC_Z_ZPHYSICALMEMORY_HPP
 
+#include "gc/z/zMemory.hpp"
 #include "memory/allocation.hpp"
-#include OS_HEADER(gc/z/zPhysicalMemoryBacking)
+#include OS_HEADER(gc/z/zBackingFile)
 
 class ZPhysicalMemorySegment : public CHeapObj<mtGC> {
 private:
@@ -65,11 +66,17 @@
 
 class ZPhysicalMemoryManager {
 private:
-  ZPhysicalMemoryBacking _backing;
+  ZBackingFile   _backing;
+  ZMemoryManager _committed;
+  ZMemoryManager _uncommitted;
 
   void nmt_commit(const ZPhysicalMemory& pmem, uintptr_t offset) const;
   void nmt_uncommit(const ZPhysicalMemory& pmem, uintptr_t offset) const;
 
+  void pretouch_view(uintptr_t addr, size_t size) const;
+  void map_view(const ZPhysicalMemory& pmem, uintptr_t addr) const;
+  void unmap_view(const ZPhysicalMemory& pmem, uintptr_t addr) const;
+
 public:
   bool is_initialized() const;