| /* |
| * 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 |