Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright (c) 2002, 2010, 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"

 // 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