jmasa@698: /*
xdono@772:  * Copyright 2002-2008 Sun Microsystems, Inc.  All Rights Reserved.
jmasa@698:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
jmasa@698:  *
jmasa@698:  * This code is free software; you can redistribute it and/or modify it
jmasa@698:  * under the terms of the GNU General Public License version 2 only, as
jmasa@698:  * published by the Free Software Foundation.
jmasa@698:  *
jmasa@698:  * This code is distributed in the hope that it will be useful, but WITHOUT
jmasa@698:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
jmasa@698:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
jmasa@698:  * version 2 for more details (a copy is included in the LICENSE file that
jmasa@698:  * accompanied this code).
jmasa@698:  *
jmasa@698:  * You should have received a copy of the GNU General Public License version
jmasa@698:  * 2 along with this work; if not, write to the Free Software Foundation,
jmasa@698:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
jmasa@698:  *
jmasa@698:  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
jmasa@698:  * CA 95054 USA or visit www.sun.com if you need additional information or
jmasa@698:  * have any questions.
jmasa@698:  *
jmasa@698:  */
jmasa@698: 
jmasa@698: # include "incls/_precompiled.incl"
jmasa@698: # include "incls/_spaceDecorator.cpp.incl"
jmasa@698: 
jmasa@698: // Catch-all file for utility classes
jmasa@698: 
jmasa@698: #ifndef PRODUCT
jmasa@698: 
jmasa@698: // Returns true is the location q matches the mangling
jmasa@698: // pattern.
jmasa@698: bool SpaceMangler::is_mangled(HeapWord* q) {
jmasa@698:   // This test loses precision but is good enough
jmasa@698:   return badHeapWord == (max_juint & (uintptr_t) q->value());
jmasa@698: }
jmasa@698: 
jmasa@698: 
jmasa@698: void SpaceMangler::set_top_for_allocations(HeapWord* v)  {
jmasa@698:   if (v < end()) {
jmasa@706:     assert(!CheckZapUnusedHeapArea || is_mangled(v),
jmasa@706:       "The high water mark is not mangled");
jmasa@698:   }
jmasa@698:   _top_for_allocations = v;
jmasa@698: }
jmasa@698: 
jmasa@698: // Mangle only the unused space that has not previously
jmasa@698: // been mangled and that has not been allocated since being
jmasa@698: // mangled.
jmasa@698: void SpaceMangler::mangle_unused_area() {
jmasa@698:   assert(ZapUnusedHeapArea, "Mangling should not be in use");
jmasa@698:   // Mangle between top and the high water mark.  Safeguard
jmasa@698:   // against the space changing since top_for_allocations was
jmasa@698:   // set.
jmasa@698:   HeapWord* mangled_end = MIN2(top_for_allocations(), end());
jmasa@698:   if (top() < mangled_end) {
jmasa@698:     MemRegion mangle_mr(top(), mangled_end);
jmasa@698:     SpaceMangler::mangle_region(mangle_mr);
jmasa@698:     // Light weight check of mangling.
jmasa@698:     check_mangled_unused_area(end());
jmasa@698:   }
jmasa@698:   // Complete check of unused area which is functional when
jmasa@698:   // DEBUG_MANGLING is defined.
jmasa@698:   check_mangled_unused_area_complete();
jmasa@698: }
jmasa@698: 
jmasa@698: // A complete mangle is expected in the
jmasa@698: // exceptional case where top_for_allocations is not
jmasa@698: // properly tracking the high water mark for mangling.
jmasa@698: // This can be the case when to-space is being used for
jmasa@698: // scratch space during a mark-sweep-compact.  See
jmasa@698: // contribute_scratch() and PSMarkSweep::allocate_stacks().
jmasa@698: void SpaceMangler::mangle_unused_area_complete() {
jmasa@698:   assert(ZapUnusedHeapArea, "Mangling should not be in use");
jmasa@698:   MemRegion mangle_mr(top(), end());
jmasa@698:   SpaceMangler::mangle_region(mangle_mr);
jmasa@698: }
jmasa@698: 
jmasa@698: // Simply mangle the MemRegion mr.
jmasa@698: void SpaceMangler::mangle_region(MemRegion mr) {
jmasa@698:   assert(ZapUnusedHeapArea, "Mangling should not be in use");
jmasa@698: #ifdef ASSERT
jmasa@698:   if(TraceZapUnusedHeapArea) {
jmasa@698:     gclog_or_tty->print("Mangling [0x%x to 0x%x)", mr.start(), mr.end());
jmasa@698:   }
jmasa@698:   Copy::fill_to_words(mr.start(), mr.word_size(), badHeapWord);
jmasa@698:   if(TraceZapUnusedHeapArea) {
jmasa@698:     gclog_or_tty->print_cr(" done");
jmasa@698:   }
jmasa@698: #endif
jmasa@698: }
jmasa@698: 
jmasa@698: // Check that top, top_for_allocations and the last
jmasa@698: // word of the space are mangled.  In a tight memory
jmasa@698: // situation even this light weight mangling could
jmasa@698: // cause paging by touching the end of the space.
jmasa@698: void  SpaceMangler::check_mangled_unused_area(HeapWord* limit) {
jmasa@698:   if (CheckZapUnusedHeapArea) {
jmasa@698:     // This method can be called while the spaces are
jmasa@698:     // being reshaped so skip the test if the end of the
jmasa@698:     // space is beyond the specified limit;
jmasa@698:     if (end() > limit) return;
jmasa@698: 
jmasa@698:     assert(top() == end() ||
jmasa@698:            (is_mangled(top())), "Top not mangled");
jmasa@698:     assert((top_for_allocations() < top()) ||
jmasa@698:            (top_for_allocations() >= end()) ||
jmasa@698:            (is_mangled(top_for_allocations())),
jmasa@698:            "Older unused not mangled");
jmasa@698:     assert(top() == end() ||
jmasa@698:            (is_mangled(end() - 1)), "End not properly mangled");
jmasa@698:     // Only does checking when DEBUG_MANGLING is defined.
jmasa@698:     check_mangled_unused_area_complete();
jmasa@698:   }
jmasa@698: }
jmasa@698: 
jmasa@698: #undef DEBUG_MANGLING
jmasa@698: // This should only be used while debugging the mangling
jmasa@698: // because of the high cost of checking the completeness.
jmasa@698: void  SpaceMangler::check_mangled_unused_area_complete() {
jmasa@698:   if (CheckZapUnusedHeapArea) {
jmasa@698:     assert(ZapUnusedHeapArea, "Not mangling unused area");
jmasa@698: #ifdef DEBUG_MANGLING
jmasa@698:     HeapWord* q = top();
jmasa@698:     HeapWord* limit = end();
jmasa@698: 
jmasa@698:     bool passed = true;
jmasa@698:     while (q < limit) {
jmasa@698:       if (!is_mangled(q)) {
jmasa@698:         passed = false;
jmasa@698:         break;
jmasa@698:       }
jmasa@698:       q++;
jmasa@698:     }
jmasa@698:     assert(passed, "Mangling is not complete");
jmasa@698: #endif
jmasa@698:   }
jmasa@698: }
jmasa@698: #undef DEBUG_MANGLING
jmasa@698: #endif // not PRODUCT