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/*
* Copyright (c) 2002, 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/shared/spaceDecorator.hpp"
#include "memory/space.inline.hpp"
#include "utilities/copy.hpp"
PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
// Catch-all file for utility classes
#ifndef PRODUCT
// Returns true is the location q matches the mangling
// pattern.
bool SpaceMangler::is_mangled(HeapWord* q) {
// This test loses precision but is good enough
return badHeapWord == (max_juint & (uintptr_t) q->value());
}
void SpaceMangler::set_top_for_allocations(HeapWord* v) {
if (v < end()) {
assert(!CheckZapUnusedHeapArea || is_mangled(v),
"The high water mark is not mangled");
}
_top_for_allocations = v;
}
// Mangle only the unused space that has not previously
// been mangled and that has not been allocated since being
// mangled.
void SpaceMangler::mangle_unused_area() {
assert(ZapUnusedHeapArea, "Mangling should not be in use");
// Mangle between top and the high water mark. Safeguard
// against the space changing since top_for_allocations was
// set.
HeapWord* mangled_end = MIN2(top_for_allocations(), end());
if (top() < mangled_end) {
MemRegion mangle_mr(top(), mangled_end);
SpaceMangler::mangle_region(mangle_mr);
// Light weight check of mangling.
check_mangled_unused_area(end());
}
// Complete check of unused area which is functional when
// DEBUG_MANGLING is defined.
check_mangled_unused_area_complete();
}
// A complete mangle is expected in the
// exceptional case where top_for_allocations is not
// properly tracking the high water mark for mangling.
// This can be the case when to-space is being used for
// scratch space during a mark-sweep-compact. See
// contribute_scratch() and PSMarkSweep::allocate_stacks().
void SpaceMangler::mangle_unused_area_complete() {
assert(ZapUnusedHeapArea, "Mangling should not be in use");
MemRegion mangle_mr(top(), end());
SpaceMangler::mangle_region(mangle_mr);
}
// Simply mangle the MemRegion mr.
void SpaceMangler::mangle_region(MemRegion mr) {
assert(ZapUnusedHeapArea, "Mangling should not be in use");
#ifdef ASSERT
if(TraceZapUnusedHeapArea) {
gclog_or_tty->print("Mangling [0x%x to 0x%x)", mr.start(), mr.end());
}
Copy::fill_to_words(mr.start(), mr.word_size(), badHeapWord);
if(TraceZapUnusedHeapArea) {
gclog_or_tty->print_cr(" done");
}
#endif
}
// Check that top, top_for_allocations and the last
// word of the space are mangled. In a tight memory
// situation even this light weight mangling could
// cause paging by touching the end of the space.
void SpaceMangler::check_mangled_unused_area(HeapWord* limit) {
if (CheckZapUnusedHeapArea) {
// This method can be called while the spaces are
// being reshaped so skip the test if the end of the
// space is beyond the specified limit;
if (end() > limit) return;
assert(top() == end() ||
(is_mangled(top())), "Top not mangled");
assert((top_for_allocations() < top()) ||
(top_for_allocations() >= end()) ||
(is_mangled(top_for_allocations())),
"Older unused not mangled");
assert(top() == end() ||
(is_mangled(end() - 1)), "End not properly mangled");
// Only does checking when DEBUG_MANGLING is defined.
check_mangled_unused_area_complete();
}
}
#undef DEBUG_MANGLING
// This should only be used while debugging the mangling
// because of the high cost of checking the completeness.
void SpaceMangler::check_mangled_unused_area_complete() {
if (CheckZapUnusedHeapArea) {
assert(ZapUnusedHeapArea, "Not mangling unused area");
#ifdef DEBUG_MANGLING
HeapWord* q = top();
HeapWord* limit = end();
bool passed = true;
while (q < limit) {
if (!is_mangled(q)) {
passed = false;
break;
}
q++;
}
assert(passed, "Mangling is not complete");
#endif
}
}
#undef DEBUG_MANGLING
#endif // not PRODUCT
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