hotspot/src/share/vm/gc_implementation/parallelScavenge/psVirtualspace.cpp - edge/openjdk - Git at Google

 /*
  * Copyright (c) 2003, 2014, 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_implementation/parallelScavenge/psVirtualspace.hpp"
 #include "runtime/os.hpp"
 #include "runtime/virtualspace.hpp"
 #ifdef TARGET_OS_FAMILY_linux
 # include "os_linux.inline.hpp"
 #endif
 #ifdef TARGET_OS_FAMILY_solaris
 # include "os_solaris.inline.hpp"
 #endif
 #ifdef TARGET_OS_FAMILY_windows
 # include "os_windows.inline.hpp"
 #endif
 #ifdef TARGET_OS_FAMILY_aix
 # include "os_aix.inline.hpp"
 #endif
 #ifdef TARGET_OS_FAMILY_bsd
 # include "os_bsd.inline.hpp"
 #endif

 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC

 // PSVirtualSpace

 PSVirtualSpace::PSVirtualSpace(ReservedSpace rs, size_t alignment) :
   _alignment(alignment)
 {
   set_reserved(rs);
   set_committed(reserved_low_addr(), reserved_low_addr());
   DEBUG_ONLY(verify());
 }

 PSVirtualSpace::PSVirtualSpace(ReservedSpace rs) :
   _alignment(os::vm_page_size())
 {
   set_reserved(rs);
   set_committed(reserved_low_addr(), reserved_low_addr());
   DEBUG_ONLY(verify());
 }

 // Deprecated.
 PSVirtualSpace::PSVirtualSpace(): _alignment(os::vm_page_size()) {
 }

 // Deprecated.
 bool PSVirtualSpace::initialize(ReservedSpace rs,
                                 size_t commit_size) {
   set_reserved(rs);
   set_committed(reserved_low_addr(), reserved_low_addr());

   // Commit to initial size.
   assert(commit_size <= rs.size(), "commit_size too big");
   bool result = commit_size > 0 ? expand_by(commit_size) : true;
   DEBUG_ONLY(verify());
   return result;
 }

 PSVirtualSpace::~PSVirtualSpace() {
   release();
 }

 bool PSVirtualSpace::contains(void* p) const {
   char* const cp = (char*)p;
   return cp >= committed_low_addr() && cp < committed_high_addr();
 }

 void PSVirtualSpace::release() {
   DEBUG_ONLY(PSVirtualSpaceVerifier this_verifier(this));
   // This may not release memory it didn't reserve.
   // Use rs.release() to release the underlying memory instead.
   _reserved_low_addr = _reserved_high_addr = NULL;
   _committed_low_addr = _committed_high_addr = NULL;
   _special = false;
 }

 bool PSVirtualSpace::expand_by(size_t bytes) {
   assert(is_aligned(bytes), "arg not aligned");
   DEBUG_ONLY(PSVirtualSpaceVerifier this_verifier(this));

   if (uncommitted_size() < bytes) {
     return false;
   }

   char* const base_addr = committed_high_addr();
   bool result = special() ||
          os::commit_memory(base_addr, bytes, alignment(), !ExecMem);
   if (result) {
     _committed_high_addr += bytes;
   }

   return result;
 }

 bool PSVirtualSpace::shrink_by(size_t bytes) {
   assert(is_aligned(bytes), "arg not aligned");
   DEBUG_ONLY(PSVirtualSpaceVerifier this_verifier(this));

   if (committed_size() < bytes) {
     return false;
   }

   char* const base_addr = committed_high_addr() - bytes;
   bool result = special() || os::uncommit_memory(base_addr, bytes);
   if (result) {
     _committed_high_addr -= bytes;
   }

   return result;
 }

 size_t
 PSVirtualSpace::expand_into(PSVirtualSpace* other_space, size_t bytes) {
   assert(is_aligned(bytes), "arg not aligned");
   assert(grows_up(), "this space must grow up");
   assert(other_space->grows_down(), "other space must grow down");
   assert(reserved_high_addr() == other_space->reserved_low_addr(),
          "spaces not contiguous");
   assert(special() == other_space->special(), "one space is special, the other is not");
   DEBUG_ONLY(PSVirtualSpaceVerifier this_verifier(this));
   DEBUG_ONLY(PSVirtualSpaceVerifier other_verifier(other_space));

   size_t bytes_needed = bytes;

   // First use the uncommitted region in this space.
   size_t tmp_bytes = MIN2(uncommitted_size(), bytes_needed);
   if (tmp_bytes > 0) {
     if (expand_by(tmp_bytes)) {
       bytes_needed -= tmp_bytes;
     } else {
       return 0;
     }
   }

   // Next take from the uncommitted region in the other space, and commit it.
   tmp_bytes = MIN2(other_space->uncommitted_size(), bytes_needed);
   if (tmp_bytes > 0) {
     char* const commit_base = committed_high_addr();
     if (other_space->special() ||
         os::commit_memory(commit_base, tmp_bytes, alignment(), !ExecMem)) {
       // Reduce the reserved region in the other space.
       other_space->set_reserved(other_space->reserved_low_addr() + tmp_bytes,
                                 other_space->reserved_high_addr(),
                                 other_space->special());

       // Grow both reserved and committed in this space.
       _reserved_high_addr += tmp_bytes;
       _committed_high_addr += tmp_bytes;
       bytes_needed -= tmp_bytes;
     } else {
       return bytes - bytes_needed;
     }
   }

   // Finally take from the already committed region in the other space.
   tmp_bytes = bytes_needed;
   if (tmp_bytes > 0) {
     // Reduce both committed and reserved in the other space.
     other_space->set_committed(other_space->committed_low_addr() + tmp_bytes,
                                other_space->committed_high_addr());
     other_space->set_reserved(other_space->reserved_low_addr() + tmp_bytes,
                               other_space->reserved_high_addr(),
                               other_space->special());

     // Grow both reserved and committed in this space.
     _reserved_high_addr += tmp_bytes;
     _committed_high_addr += tmp_bytes;
   }

   return bytes;
 }

 #ifndef PRODUCT
 bool PSVirtualSpace::is_aligned(size_t value, size_t align) {
   const size_t tmp_value = value + align - 1;
   const size_t mask = ~(align - 1);
   return (tmp_value & mask) == value;
 }

 bool PSVirtualSpace::is_aligned(size_t value) const {
   return is_aligned(value, alignment());
 }

 bool PSVirtualSpace::is_aligned(char* value) const {
   return is_aligned((size_t)value);
 }

 void PSVirtualSpace::verify() const {
   assert(is_aligned(alignment(), os::vm_page_size()), "bad alignment");
   assert(is_aligned(reserved_low_addr()), "bad reserved_low_addr");
   assert(is_aligned(reserved_high_addr()), "bad reserved_high_addr");
   assert(is_aligned(committed_low_addr()), "bad committed_low_addr");
   assert(is_aligned(committed_high_addr()), "bad committed_high_addr");

   // Reserved region must be non-empty or both addrs must be 0.
   assert(reserved_low_addr() < reserved_high_addr() ||
          reserved_low_addr() == NULL && reserved_high_addr() == NULL,
          "bad reserved addrs");
   assert(committed_low_addr() <= committed_high_addr(), "bad committed addrs");

   if (grows_up()) {
     assert(reserved_low_addr() == committed_low_addr(), "bad low addrs");
     assert(reserved_high_addr() >= committed_high_addr(), "bad high addrs");
   } else {
     assert(reserved_high_addr() == committed_high_addr(), "bad high addrs");
     assert(reserved_low_addr() <= committed_low_addr(), "bad low addrs");
   }
 }

 void PSVirtualSpace::print() const {
   gclog_or_tty->print_cr("virtual space [" PTR_FORMAT "]:  alignment="
                          SIZE_FORMAT "K grows %s%s",
                          this, alignment() / K, grows_up() ? "up" : "down",
                          special() ? " (pinned in memory)" : "");
   gclog_or_tty->print_cr("    reserved=" SIZE_FORMAT "K"
                          " [" PTR_FORMAT "," PTR_FORMAT "]"
                          " committed=" SIZE_FORMAT "K"
                          " [" PTR_FORMAT "," PTR_FORMAT "]",
                          reserved_size() / K,
                          reserved_low_addr(), reserved_high_addr(),
                          committed_size() / K,
                          committed_low_addr(), committed_high_addr());
 }
 #endif // #ifndef PRODUCT

 void PSVirtualSpace::print_space_boundaries_on(outputStream* st) const {
   st->print_cr(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")",
                low_boundary(), high(), high_boundary());
 }

 PSVirtualSpaceHighToLow::PSVirtualSpaceHighToLow(ReservedSpace rs,
                                                  size_t alignment) :
   PSVirtualSpace(alignment)
 {
   set_reserved(rs);
   set_committed(reserved_high_addr(), reserved_high_addr());
   DEBUG_ONLY(verify());
 }

 PSVirtualSpaceHighToLow::PSVirtualSpaceHighToLow(ReservedSpace rs) {
   set_reserved(rs);
   set_committed(reserved_high_addr(), reserved_high_addr());
   DEBUG_ONLY(verify());
 }

 bool PSVirtualSpaceHighToLow::expand_by(size_t bytes) {
   assert(is_aligned(bytes), "arg not aligned");
   DEBUG_ONLY(PSVirtualSpaceVerifier this_verifier(this));

   if (uncommitted_size() < bytes) {
     return false;
   }

   char* const base_addr = committed_low_addr() - bytes;
   bool result = special() ||
          os::commit_memory(base_addr, bytes, alignment(), !ExecMem);
   if (result) {
     _committed_low_addr -= bytes;
   }

   return result;
 }

 bool PSVirtualSpaceHighToLow::shrink_by(size_t bytes) {
   assert(is_aligned(bytes), "arg not aligned");
   DEBUG_ONLY(PSVirtualSpaceVerifier this_verifier(this));

   if (committed_size() < bytes) {
     return false;
   }

   char* const base_addr = committed_low_addr();
   bool result = special() || os::uncommit_memory(base_addr, bytes);
   if (result) {
     _committed_low_addr += bytes;
   }

   return result;
 }

 size_t PSVirtualSpaceHighToLow::expand_into(PSVirtualSpace* other_space,
                                             size_t bytes) {
   assert(is_aligned(bytes), "arg not aligned");
   assert(grows_down(), "this space must grow down");
   assert(other_space->grows_up(), "other space must grow up");
   assert(reserved_low_addr() == other_space->reserved_high_addr(),
          "spaces not contiguous");
   assert(special() == other_space->special(), "one space is special in memory, the other is not");
   DEBUG_ONLY(PSVirtualSpaceVerifier this_verifier(this));
   DEBUG_ONLY(PSVirtualSpaceVerifier other_verifier(other_space));

   size_t bytes_needed = bytes;

   // First use the uncommitted region in this space.
   size_t tmp_bytes = MIN2(uncommitted_size(), bytes_needed);
   if (tmp_bytes > 0) {
     if (expand_by(tmp_bytes)) {
       bytes_needed -= tmp_bytes;
     } else {
       return 0;
     }
   }

   // Next take from the uncommitted region in the other space, and commit it.
   tmp_bytes = MIN2(other_space->uncommitted_size(), bytes_needed);
   if (tmp_bytes > 0) {
     char* const commit_base = committed_low_addr() - tmp_bytes;
     if (other_space->special() ||
         os::commit_memory(commit_base, tmp_bytes, alignment(), !ExecMem)) {
       // Reduce the reserved region in the other space.
       other_space->set_reserved(other_space->reserved_low_addr(),
                                 other_space->reserved_high_addr() - tmp_bytes,
                                 other_space->special());

       // Grow both reserved and committed in this space.
       _reserved_low_addr -= tmp_bytes;
       _committed_low_addr -= tmp_bytes;
       bytes_needed -= tmp_bytes;
     } else {
       return bytes - bytes_needed;
     }
   }

   // Finally take from the already committed region in the other space.
   tmp_bytes = bytes_needed;
   if (tmp_bytes > 0) {
     // Reduce both committed and reserved in the other space.
     other_space->set_committed(other_space->committed_low_addr(),
                                other_space->committed_high_addr() - tmp_bytes);
     other_space->set_reserved(other_space->reserved_low_addr(),
                               other_space->reserved_high_addr() - tmp_bytes,
                               other_space->special());

     // Grow both reserved and committed in this space.
     _reserved_low_addr -= tmp_bytes;
     _committed_low_addr -= tmp_bytes;
   }

   return bytes;
 }

 void
 PSVirtualSpaceHighToLow::print_space_boundaries_on(outputStream* st) const {
   st->print_cr(" (" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT "]",
                high_boundary(), low(), low_boundary());
 }
	/*
	* Copyright (c) 2003, 2014, 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_implementation/parallelScavenge/psVirtualspace.hpp"
	#include "runtime/os.hpp"
	#include "runtime/virtualspace.hpp"
	#ifdef TARGET_OS_FAMILY_linux
	# include "os_linux.inline.hpp"
	#endif
	#ifdef TARGET_OS_FAMILY_solaris
	# include "os_solaris.inline.hpp"
	#endif
	#ifdef TARGET_OS_FAMILY_windows
	# include "os_windows.inline.hpp"
	#endif
	#ifdef TARGET_OS_FAMILY_aix
	# include "os_aix.inline.hpp"
	#endif
	#ifdef TARGET_OS_FAMILY_bsd
	# include "os_bsd.inline.hpp"
	#endif

	PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC

	// PSVirtualSpace

	PSVirtualSpace::PSVirtualSpace(ReservedSpace rs, size_t alignment) :
	_alignment(alignment)
	{
	set_reserved(rs);
	set_committed(reserved_low_addr(), reserved_low_addr());
	DEBUG_ONLY(verify());
	}

	PSVirtualSpace::PSVirtualSpace(ReservedSpace rs) :
	_alignment(os::vm_page_size())
	{
	set_reserved(rs);
	set_committed(reserved_low_addr(), reserved_low_addr());
	DEBUG_ONLY(verify());
	}

	// Deprecated.
	PSVirtualSpace::PSVirtualSpace(): _alignment(os::vm_page_size()) {
	}

	// Deprecated.
	bool PSVirtualSpace::initialize(ReservedSpace rs,
	size_t commit_size) {
	set_reserved(rs);
	set_committed(reserved_low_addr(), reserved_low_addr());

	// Commit to initial size.
	assert(commit_size <= rs.size(), "commit_size too big");
	bool result = commit_size > 0 ? expand_by(commit_size) : true;
	DEBUG_ONLY(verify());
	return result;
	}

	PSVirtualSpace::~PSVirtualSpace() {
	release();
	}

	bool PSVirtualSpace::contains(void* p) const {
	char* const cp = (char*)p;
	return cp >= committed_low_addr() && cp < committed_high_addr();
	}

	void PSVirtualSpace::release() {
	DEBUG_ONLY(PSVirtualSpaceVerifier this_verifier(this));
	// This may not release memory it didn't reserve.
	// Use rs.release() to release the underlying memory instead.
	_reserved_low_addr = _reserved_high_addr = NULL;
	_committed_low_addr = _committed_high_addr = NULL;
	_special = false;
	}

	bool PSVirtualSpace::expand_by(size_t bytes) {
	assert(is_aligned(bytes), "arg not aligned");
	DEBUG_ONLY(PSVirtualSpaceVerifier this_verifier(this));

	if (uncommitted_size() < bytes) {
	return false;
	}

	char* const base_addr = committed_high_addr();
	bool result = special() \|\|
	os::commit_memory(base_addr, bytes, alignment(), !ExecMem);
	if (result) {
	_committed_high_addr += bytes;
	}

	return result;
	}

	bool PSVirtualSpace::shrink_by(size_t bytes) {
	assert(is_aligned(bytes), "arg not aligned");
	DEBUG_ONLY(PSVirtualSpaceVerifier this_verifier(this));

	if (committed_size() < bytes) {
	return false;
	}

	char* const base_addr = committed_high_addr() - bytes;
	bool result = special() \|\| os::uncommit_memory(base_addr, bytes);
	if (result) {
	_committed_high_addr -= bytes;
	}

	return result;
	}

	size_t
	PSVirtualSpace::expand_into(PSVirtualSpace* other_space, size_t bytes) {
	assert(is_aligned(bytes), "arg not aligned");
	assert(grows_up(), "this space must grow up");
	assert(other_space->grows_down(), "other space must grow down");
	assert(reserved_high_addr() == other_space->reserved_low_addr(),
	"spaces not contiguous");
	assert(special() == other_space->special(), "one space is special, the other is not");
	DEBUG_ONLY(PSVirtualSpaceVerifier this_verifier(this));
	DEBUG_ONLY(PSVirtualSpaceVerifier other_verifier(other_space));

	size_t bytes_needed = bytes;

	// First use the uncommitted region in this space.
	size_t tmp_bytes = MIN2(uncommitted_size(), bytes_needed);
	if (tmp_bytes > 0) {
	if (expand_by(tmp_bytes)) {
	bytes_needed -= tmp_bytes;
	} else {
	return 0;
	}
	}

	// Next take from the uncommitted region in the other space, and commit it.
	tmp_bytes = MIN2(other_space->uncommitted_size(), bytes_needed);
	if (tmp_bytes > 0) {
	char* const commit_base = committed_high_addr();
	if (other_space->special() \|\|
	os::commit_memory(commit_base, tmp_bytes, alignment(), !ExecMem)) {
	// Reduce the reserved region in the other space.
	other_space->set_reserved(other_space->reserved_low_addr() + tmp_bytes,
	other_space->reserved_high_addr(),
	other_space->special());

	// Grow both reserved and committed in this space.
	_reserved_high_addr += tmp_bytes;
	_committed_high_addr += tmp_bytes;
	bytes_needed -= tmp_bytes;
	} else {
	return bytes - bytes_needed;
	}
	}

	// Finally take from the already committed region in the other space.
	tmp_bytes = bytes_needed;
	if (tmp_bytes > 0) {
	// Reduce both committed and reserved in the other space.
	other_space->set_committed(other_space->committed_low_addr() + tmp_bytes,
	other_space->committed_high_addr());
	other_space->set_reserved(other_space->reserved_low_addr() + tmp_bytes,
	other_space->reserved_high_addr(),
	other_space->special());

	// Grow both reserved and committed in this space.
	_reserved_high_addr += tmp_bytes;
	_committed_high_addr += tmp_bytes;
	}

	return bytes;
	}

	#ifndef PRODUCT
	bool PSVirtualSpace::is_aligned(size_t value, size_t align) {
	const size_t tmp_value = value + align - 1;
	const size_t mask = ~(align - 1);
	return (tmp_value & mask) == value;
	}

	bool PSVirtualSpace::is_aligned(size_t value) const {
	return is_aligned(value, alignment());
	}

	bool PSVirtualSpace::is_aligned(char* value) const {
	return is_aligned((size_t)value);
	}

	void PSVirtualSpace::verify() const {
	assert(is_aligned(alignment(), os::vm_page_size()), "bad alignment");
	assert(is_aligned(reserved_low_addr()), "bad reserved_low_addr");
	assert(is_aligned(reserved_high_addr()), "bad reserved_high_addr");
	assert(is_aligned(committed_low_addr()), "bad committed_low_addr");
	assert(is_aligned(committed_high_addr()), "bad committed_high_addr");

	// Reserved region must be non-empty or both addrs must be 0.
	assert(reserved_low_addr() < reserved_high_addr() \|\|
	reserved_low_addr() == NULL && reserved_high_addr() == NULL,
	"bad reserved addrs");
	assert(committed_low_addr() <= committed_high_addr(), "bad committed addrs");

	if (grows_up()) {
	assert(reserved_low_addr() == committed_low_addr(), "bad low addrs");
	assert(reserved_high_addr() >= committed_high_addr(), "bad high addrs");
	} else {
	assert(reserved_high_addr() == committed_high_addr(), "bad high addrs");
	assert(reserved_low_addr() <= committed_low_addr(), "bad low addrs");
	}
	}

	void PSVirtualSpace::print() const {
	gclog_or_tty->print_cr("virtual space [" PTR_FORMAT "]: alignment="
	SIZE_FORMAT "K grows %s%s",
	this, alignment() / K, grows_up() ? "up" : "down",
	special() ? " (pinned in memory)" : "");
	gclog_or_tty->print_cr(" reserved=" SIZE_FORMAT "K"
	" [" PTR_FORMAT "," PTR_FORMAT "]"
	" committed=" SIZE_FORMAT "K"
	" [" PTR_FORMAT "," PTR_FORMAT "]",
	reserved_size() / K,
	reserved_low_addr(), reserved_high_addr(),
	committed_size() / K,
	committed_low_addr(), committed_high_addr());
	}
	#endif // #ifndef PRODUCT

	void PSVirtualSpace::print_space_boundaries_on(outputStream* st) const {
	st->print_cr(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")",
	low_boundary(), high(), high_boundary());
	}

	PSVirtualSpaceHighToLow::PSVirtualSpaceHighToLow(ReservedSpace rs,
	size_t alignment) :
	PSVirtualSpace(alignment)
	{
	set_reserved(rs);
	set_committed(reserved_high_addr(), reserved_high_addr());
	DEBUG_ONLY(verify());
	}

	PSVirtualSpaceHighToLow::PSVirtualSpaceHighToLow(ReservedSpace rs) {
	set_reserved(rs);
	set_committed(reserved_high_addr(), reserved_high_addr());
	DEBUG_ONLY(verify());
	}

	bool PSVirtualSpaceHighToLow::expand_by(size_t bytes) {
	assert(is_aligned(bytes), "arg not aligned");
	DEBUG_ONLY(PSVirtualSpaceVerifier this_verifier(this));

	if (uncommitted_size() < bytes) {
	return false;
	}

	char* const base_addr = committed_low_addr() - bytes;
	bool result = special() \|\|
	os::commit_memory(base_addr, bytes, alignment(), !ExecMem);
	if (result) {
	_committed_low_addr -= bytes;
	}

	return result;
	}

	bool PSVirtualSpaceHighToLow::shrink_by(size_t bytes) {
	assert(is_aligned(bytes), "arg not aligned");
	DEBUG_ONLY(PSVirtualSpaceVerifier this_verifier(this));

	if (committed_size() < bytes) {
	return false;
	}

	char* const base_addr = committed_low_addr();
	bool result = special() \|\| os::uncommit_memory(base_addr, bytes);
	if (result) {
	_committed_low_addr += bytes;
	}

	return result;
	}

	size_t PSVirtualSpaceHighToLow::expand_into(PSVirtualSpace* other_space,
	size_t bytes) {
	assert(is_aligned(bytes), "arg not aligned");
	assert(grows_down(), "this space must grow down");
	assert(other_space->grows_up(), "other space must grow up");
	assert(reserved_low_addr() == other_space->reserved_high_addr(),
	"spaces not contiguous");
	assert(special() == other_space->special(), "one space is special in memory, the other is not");
	DEBUG_ONLY(PSVirtualSpaceVerifier this_verifier(this));
	DEBUG_ONLY(PSVirtualSpaceVerifier other_verifier(other_space));

	size_t bytes_needed = bytes;

	// First use the uncommitted region in this space.
	size_t tmp_bytes = MIN2(uncommitted_size(), bytes_needed);
	if (tmp_bytes > 0) {
	if (expand_by(tmp_bytes)) {
	bytes_needed -= tmp_bytes;
	} else {
	return 0;
	}
	}

	// Next take from the uncommitted region in the other space, and commit it.
	tmp_bytes = MIN2(other_space->uncommitted_size(), bytes_needed);
	if (tmp_bytes > 0) {
	char* const commit_base = committed_low_addr() - tmp_bytes;
	if (other_space->special() \|\|
	os::commit_memory(commit_base, tmp_bytes, alignment(), !ExecMem)) {
	// Reduce the reserved region in the other space.
	other_space->set_reserved(other_space->reserved_low_addr(),
	other_space->reserved_high_addr() - tmp_bytes,
	other_space->special());

	// Grow both reserved and committed in this space.
	_reserved_low_addr -= tmp_bytes;
	_committed_low_addr -= tmp_bytes;
	bytes_needed -= tmp_bytes;
	} else {
	return bytes - bytes_needed;
	}
	}

	// Finally take from the already committed region in the other space.
	tmp_bytes = bytes_needed;
	if (tmp_bytes > 0) {
	// Reduce both committed and reserved in the other space.
	other_space->set_committed(other_space->committed_low_addr(),
	other_space->committed_high_addr() - tmp_bytes);
	other_space->set_reserved(other_space->reserved_low_addr(),
	other_space->reserved_high_addr() - tmp_bytes,
	other_space->special());

	// Grow both reserved and committed in this space.
	_reserved_low_addr -= tmp_bytes;
	_committed_low_addr -= tmp_bytes;
	}

	return bytes;
	}

	void
	PSVirtualSpaceHighToLow::print_space_boundaries_on(outputStream* st) const {
	st->print_cr(" (" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT "]",
	high_boundary(), low(), low_boundary());
	}