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 /*

  * Copyright (c) 2001, 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

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  */

 #include "precompiled.hpp"

 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.hpp"

 #include "gc_implementation/parallelScavenge/psMarkSweepDecorator.hpp"

 #include "gc_implementation/parallelScavenge/psScavenge.hpp"

 #include "gc_implementation/parallelScavenge/psYoungGen.hpp"

 #include "gc_implementation/shared/gcUtil.hpp"

 #include "gc_implementation/shared/mutableNUMASpace.hpp"

 #include "gc_implementation/shared/spaceDecorator.hpp"

 #include "oops/oop.inline.hpp"

 #include "runtime/java.hpp"

 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC

 PSYoungGen::PSYoungGen(size_t        initial_size,

                        size_t        min_size,

                        size_t        max_size) :

   _init_gen_size(initial_size),

   _min_gen_size(min_size),

   _max_gen_size(max_size)

 {}

 void PSYoungGen::initialize_virtual_space(ReservedSpace rs, size_t alignment) {

   assert(_init_gen_size != 0, "Should have a finite size");

   _virtual_space = new PSVirtualSpace(rs, alignment);

   if (!virtual_space()->expand_by(_init_gen_size)) {

     vm_exit_during_initialization("Could not reserve enough space for "

                                   "object heap");

   }

 }

 void PSYoungGen::initialize(ReservedSpace rs, size_t alignment) {

   initialize_virtual_space(rs, alignment);

   initialize_work();

 }

 void PSYoungGen::initialize_work() {

   _reserved = MemRegion((HeapWord*)virtual_space()->low_boundary(),

                         (HeapWord*)virtual_space()->high_boundary());

   MemRegion cmr((HeapWord*)virtual_space()->low(),

                 (HeapWord*)virtual_space()->high());

   Universe::heap()->barrier_set()->resize_covered_region(cmr);

   if (ZapUnusedHeapArea) {

     // Mangle newly committed space immediately because it

     // can be done here more simply that after the new

     // spaces have been computed.

     SpaceMangler::mangle_region(cmr);

   }

   if (UseNUMA) {

     _eden_space = new MutableNUMASpace(virtual_space()->alignment());

   } else {

     _eden_space = new MutableSpace(virtual_space()->alignment());

   }

   _from_space = new MutableSpace(virtual_space()->alignment());

   _to_space   = new MutableSpace(virtual_space()->alignment());

   if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) {

     vm_exit_during_initialization("Could not allocate a young gen space");

   }

   // Allocate the mark sweep views of spaces

   _eden_mark_sweep =

       new PSMarkSweepDecorator(_eden_space, NULL, MarkSweepDeadRatio);

   _from_mark_sweep =

       new PSMarkSweepDecorator(_from_space, NULL, MarkSweepDeadRatio);

   _to_mark_sweep =

       new PSMarkSweepDecorator(_to_space, NULL, MarkSweepDeadRatio);

   if (_eden_mark_sweep == NULL ||

       _from_mark_sweep == NULL ||

       _to_mark_sweep == NULL) {

     vm_exit_during_initialization("Could not complete allocation"

                                   " of the young generation");

   }

   // Generation Counters - generation 0, 3 subspaces

   _gen_counters = new PSGenerationCounters("new", 0, 3, _virtual_space);

   // Compute maximum space sizes for performance counters

   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();

   size_t alignment = heap->space_alignment();

   size_t size = virtual_space()->reserved_size();

   size_t max_survivor_size;

   size_t max_eden_size;

   if (UseAdaptiveSizePolicy) {

     max_survivor_size = size / MinSurvivorRatio;

     // round the survivor space size down to the nearest alignment

     // and make sure its size is greater than 0.

     max_survivor_size = align_size_down(max_survivor_size, alignment);

     max_survivor_size = MAX2(max_survivor_size, alignment);

     // set the maximum size of eden to be the size of the young gen

     // less two times the minimum survivor size. The minimum survivor

     // size for UseAdaptiveSizePolicy is one alignment.

     max_eden_size = size - 2 * alignment;

   } else {

     max_survivor_size = size / InitialSurvivorRatio;

     // round the survivor space size down to the nearest alignment

     // and make sure its size is greater than 0.

     max_survivor_size = align_size_down(max_survivor_size, alignment);

     max_survivor_size = MAX2(max_survivor_size, alignment);

     // set the maximum size of eden to be the size of the young gen

     // less two times the survivor size when the generation is 100%

     // committed. The minimum survivor size for -UseAdaptiveSizePolicy

     // is dependent on the committed portion (current capacity) of the

     // generation - the less space committed, the smaller the survivor

     // space, possibly as small as an alignment. However, we are interested

     // in the case where the young generation is 100% committed, as this

     // is the point where eden reachs its maximum size. At this point,

     // the size of a survivor space is max_survivor_size.

     max_eden_size = size - 2 * max_survivor_size;

   }

   _eden_counters = new SpaceCounters("eden", 0, max_eden_size, _eden_space,

                                      _gen_counters);

   _from_counters = new SpaceCounters("s0", 1, max_survivor_size, _from_space,

                                      _gen_counters);

   _to_counters = new SpaceCounters("s1", 2, max_survivor_size, _to_space,

                                    _gen_counters);

   compute_initial_space_boundaries();

 }

 void PSYoungGen::compute_initial_space_boundaries() {

   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();

   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");

   // Compute sizes

   size_t alignment = heap->space_alignment();

   size_t size = virtual_space()->committed_size();

   assert(size >= 3 * alignment, "Young space is not large enough for eden + 2 survivors");

   size_t survivor_size = size / InitialSurvivorRatio;

   survivor_size = align_size_down(survivor_size, alignment);

   // ... but never less than an alignment

   survivor_size = MAX2(survivor_size, alignment);

   // Young generation is eden + 2 survivor spaces

   size_t eden_size = size - (2 * survivor_size);

   // Now go ahead and set 'em.

   set_space_boundaries(eden_size, survivor_size);

   space_invariants();

   if (UsePerfData) {

     _eden_counters->update_capacity();

     _from_counters->update_capacity();

     _to_counters->update_capacity();

   }

 }

 void PSYoungGen::set_space_boundaries(size_t eden_size, size_t survivor_size) {

   assert(eden_size < virtual_space()->committed_size(), "just checking");

   assert(eden_size > 0  && survivor_size > 0, "just checking");

   // Initial layout is Eden, to, from. After swapping survivor spaces,

   // that leaves us with Eden, from, to, which is step one in our two

   // step resize-with-live-data procedure.

   char *eden_start = virtual_space()->low();

   char *to_start   = eden_start + eden_size;

   char *from_start = to_start   + survivor_size;

   char *from_end   = from_start + survivor_size;

   assert(from_end == virtual_space()->high(), "just checking");

   assert(is_object_aligned((intptr_t)eden_start), "checking alignment");

   assert(is_object_aligned((intptr_t)to_start),   "checking alignment");

   assert(is_object_aligned((intptr_t)from_start), "checking alignment");

   MemRegion eden_mr((HeapWord*)eden_start, (HeapWord*)to_start);

   MemRegion to_mr  ((HeapWord*)to_start, (HeapWord*)from_start);

   MemRegion from_mr((HeapWord*)from_start, (HeapWord*)from_end);

   eden_space()->initialize(eden_mr, true, ZapUnusedHeapArea);

     to_space()->initialize(to_mr  , true, ZapUnusedHeapArea);

   from_space()->initialize(from_mr, true, ZapUnusedHeapArea);

 }

 #ifndef PRODUCT

 void PSYoungGen::space_invariants() {

   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();

   const size_t alignment = heap->space_alignment();

   // Currently, our eden size cannot shrink to zero

   guarantee(eden_space()->capacity_in_bytes() >= alignment, "eden too small");

   guarantee(from_space()->capacity_in_bytes() >= alignment, "from too small");

   guarantee(to_space()->capacity_in_bytes() >= alignment, "to too small");

   // Relationship of spaces to each other

   char* eden_start = (char*)eden_space()->bottom();

   char* eden_end   = (char*)eden_space()->end();

   char* from_start = (char*)from_space()->bottom();

   char* from_end   = (char*)from_space()->end();

   char* to_start   = (char*)to_space()->bottom();

   char* to_end     = (char*)to_space()->end();

   guarantee(eden_start >= virtual_space()->low(), "eden bottom");

   guarantee(eden_start < eden_end, "eden space consistency");

   guarantee(from_start < from_end, "from space consistency");

   guarantee(to_start < to_end, "to space consistency");

   // Check whether from space is below to space

   if (from_start < to_start) {

     // Eden, from, to

     guarantee(eden_end <= from_start, "eden/from boundary");

     guarantee(from_end <= to_start,   "from/to boundary");

     guarantee(to_end <= virtual_space()->high(), "to end");

   } else {

     // Eden, to, from

     guarantee(eden_end <= to_start, "eden/to boundary");

     guarantee(to_end <= from_start, "to/from boundary");

     guarantee(from_end <= virtual_space()->high(), "from end");

   }

   // More checks that the virtual space is consistent with the spaces

   assert(virtual_space()->committed_size() >=

     (eden_space()->capacity_in_bytes() +

      to_space()->capacity_in_bytes() +

      from_space()->capacity_in_bytes()), "Committed size is inconsistent");

   assert(virtual_space()->committed_size() <= virtual_space()->reserved_size(),

     "Space invariant");

   char* eden_top = (char*)eden_space()->top();

   char* from_top = (char*)from_space()->top();

   char* to_top = (char*)to_space()->top();

   assert(eden_top <= virtual_space()->high(), "eden top");

   assert(from_top <= virtual_space()->high(), "from top");

   assert(to_top <= virtual_space()->high(), "to top");

   virtual_space()->verify();

 }

 #endif

 void PSYoungGen::resize(size_t eden_size, size_t survivor_size) {

   // Resize the generation if needed. If the generation resize

   // reports false, do not attempt to resize the spaces.

   if (resize_generation(eden_size, survivor_size)) {

     // Then we lay out the spaces inside the generation

     resize_spaces(eden_size, survivor_size);

     space_invariants();

     if (PrintAdaptiveSizePolicy && Verbose) {

       gclog_or_tty->print_cr("Young generation size: "

         "desired eden: " SIZE_FORMAT " survivor: " SIZE_FORMAT

         " used: " SIZE_FORMAT " capacity: " SIZE_FORMAT

         " gen limits: " SIZE_FORMAT " / " SIZE_FORMAT,

         eden_size, survivor_size, used_in_bytes(), capacity_in_bytes(),

         _max_gen_size, min_gen_size());

     }

   }

 }

 bool PSYoungGen::resize_generation(size_t eden_size, size_t survivor_size) {

   const size_t alignment = virtual_space()->alignment();

   size_t orig_size = virtual_space()->committed_size();

   bool size_changed = false;

   // There used to be this guarantee there.

   // guarantee ((eden_size + 2*survivor_size)  <= _max_gen_size, "incorrect input arguments");

   // Code below forces this requirement.  In addition the desired eden

   // size and disired survivor sizes are desired goals and may

   // exceed the total generation size.

   assert(min_gen_size() <= orig_size && orig_size <= max_size(), "just checking");

   // Adjust new generation size

   const size_t eden_plus_survivors =

           align_size_up(eden_size + 2 * survivor_size, alignment);

   size_t desired_size = MAX2(MIN2(eden_plus_survivors, max_size()),

                              min_gen_size());

   assert(desired_size <= max_size(), "just checking");

   if (desired_size > orig_size) {

     // Grow the generation

     size_t change = desired_size - orig_size;

     assert(change % alignment == 0, "just checking");

     HeapWord* prev_high = (HeapWord*) virtual_space()->high();

     if (!virtual_space()->expand_by(change)) {

       return false; // Error if we fail to resize!

     }

     if (ZapUnusedHeapArea) {

       // Mangle newly committed space immediately because it

       // can be done here more simply that after the new

       // spaces have been computed.

       HeapWord* new_high = (HeapWord*) virtual_space()->high();

       MemRegion mangle_region(prev_high, new_high);

       SpaceMangler::mangle_region(mangle_region);

     }

     size_changed = true;

   } else if (desired_size < orig_size) {

     size_t desired_change = orig_size - desired_size;

     assert(desired_change % alignment == 0, "just checking");

     desired_change = limit_gen_shrink(desired_change);

     if (desired_change > 0) {

       virtual_space()->shrink_by(desired_change);

       reset_survivors_after_shrink();

       size_changed = true;

     }

   } else {

     if (Verbose && PrintGC) {

       if (orig_size == gen_size_limit()) {

         gclog_or_tty->print_cr("PSYoung generation size at maximum: "

           SIZE_FORMAT "K", orig_size/K);

       } else if (orig_size == min_gen_size()) {

         gclog_or_tty->print_cr("PSYoung generation size at minium: "

           SIZE_FORMAT "K", orig_size/K);

       }

     }

   }

   if (size_changed) {

     post_resize();

     if (Verbose && PrintGC) {

       size_t current_size  = virtual_space()->committed_size();

       gclog_or_tty->print_cr("PSYoung generation size changed: "

                              SIZE_FORMAT "K->" SIZE_FORMAT "K",

                              orig_size/K, current_size/K);

     }

   }

   guarantee(eden_plus_survivors <= virtual_space()->committed_size() ||

             virtual_space()->committed_size() == max_size(), "Sanity");

   return true;

 }

 #ifndef PRODUCT

 // In the numa case eden is not mangled so a survivor space

 // moving into a region previously occupied by a survivor

 // may find an unmangled region.  Also in the PS case eden

 // to-space and from-space may not touch (i.e., there may be

 // gaps between them due to movement while resizing the

 // spaces).  Those gaps must be mangled.

 void PSYoungGen::mangle_survivors(MutableSpace* s1,

                                   MemRegion s1MR,

                                   MutableSpace* s2,

                                   MemRegion s2MR) {

   // Check eden and gap between eden and from-space, in deciding

   // what to mangle in from-space.  Check the gap between from-space

   // and to-space when deciding what to mangle.

   //

   //      +--------+   +----+    +---+

   //      | eden   |   |s1  |    |s2 |

   //      +--------+   +----+    +---+

   //                 +-------+ +-----+

   //                 |s1MR   | |s2MR |

   //                 +-------+ +-----+

   // All of survivor-space is properly mangled so find the

   // upper bound on the mangling for any portion above current s1.

   HeapWord* delta_end = MIN2(s1->bottom(), s1MR.end());

   MemRegion delta1_left;

   if (s1MR.start() < delta_end) {

     delta1_left = MemRegion(s1MR.start(), delta_end);

     s1->mangle_region(delta1_left);

   }

   // Find any portion to the right of the current s1.

   HeapWord* delta_start = MAX2(s1->end(), s1MR.start());

   MemRegion delta1_right;

   if (delta_start < s1MR.end()) {

     delta1_right = MemRegion(delta_start, s1MR.end());

     s1->mangle_region(delta1_right);

   }

   // Similarly for the second survivor space except that

   // any of the new region that overlaps with the current

   // region of the first survivor space has already been

   // mangled.

   delta_end = MIN2(s2->bottom(), s2MR.end());

   delta_start = MAX2(s2MR.start(), s1->end());

   MemRegion delta2_left;

   if (s2MR.start() < delta_end) {

     delta2_left = MemRegion(s2MR.start(), delta_end);

     s2->mangle_region(delta2_left);

   }

   delta_start = MAX2(s2->end(), s2MR.start());

   MemRegion delta2_right;

   if (delta_start < s2MR.end()) {

     s2->mangle_region(delta2_right);

   }

   if (TraceZapUnusedHeapArea) {

     // s1

     gclog_or_tty->print_cr("Current region: [" PTR_FORMAT ", " PTR_FORMAT ") "

       "New region: [" PTR_FORMAT ", " PTR_FORMAT ")",

       s1->bottom(), s1->end(), s1MR.start(), s1MR.end());

     gclog_or_tty->print_cr("    Mangle before: [" PTR_FORMAT ", "

       PTR_FORMAT ")  Mangle after: [" PTR_FORMAT ", " PTR_FORMAT ")",

       delta1_left.start(), delta1_left.end(), delta1_right.start(),

       delta1_right.end());

     // s2

     gclog_or_tty->print_cr("Current region: [" PTR_FORMAT ", " PTR_FORMAT ") "

       "New region: [" PTR_FORMAT ", " PTR_FORMAT ")",

       s2->bottom(), s2->end(), s2MR.start(), s2MR.end());

     gclog_or_tty->print_cr("    Mangle before: [" PTR_FORMAT ", "

       PTR_FORMAT ")  Mangle after: [" PTR_FORMAT ", " PTR_FORMAT ")",

       delta2_left.start(), delta2_left.end(), delta2_right.start(),

       delta2_right.end());

   }

 }

 #endif // NOT PRODUCT

 void PSYoungGen::resize_spaces(size_t requested_eden_size,

                                size_t requested_survivor_size) {

   assert(UseAdaptiveSizePolicy, "sanity check");

   assert(requested_eden_size > 0  && requested_survivor_size > 0,

          "just checking");

   // We require eden and to space to be empty

   if ((!eden_space()->is_empty()) || (!to_space()->is_empty())) {

     return;

   }

   if (PrintAdaptiveSizePolicy && Verbose) {

     gclog_or_tty->print_cr("PSYoungGen::resize_spaces(requested_eden_size: "

                   SIZE_FORMAT

                   ", requested_survivor_size: " SIZE_FORMAT ")",

                   requested_eden_size, requested_survivor_size);

     gclog_or_tty->print_cr("    eden: [" PTR_FORMAT ".." PTR_FORMAT ") "

                   SIZE_FORMAT,

                   eden_space()->bottom(),

                   eden_space()->end(),

                   pointer_delta(eden_space()->end(),

                                 eden_space()->bottom(),

                                 sizeof(char)));

     gclog_or_tty->print_cr("    from: [" PTR_FORMAT ".." PTR_FORMAT ") "

                   SIZE_FORMAT,

                   from_space()->bottom(),

                   from_space()->end(),

                   pointer_delta(from_space()->end(),

                                 from_space()->bottom(),

                                 sizeof(char)));

     gclog_or_tty->print_cr("      to: [" PTR_FORMAT ".." PTR_FORMAT ") "

                   SIZE_FORMAT,

                   to_space()->bottom(),

                   to_space()->end(),

                   pointer_delta(  to_space()->end(),

                                   to_space()->bottom(),

                                   sizeof(char)));

   }

   // There's nothing to do if the new sizes are the same as the current

   if (requested_survivor_size == to_space()->capacity_in_bytes() &&

       requested_survivor_size == from_space()->capacity_in_bytes() &&

       requested_eden_size == eden_space()->capacity_in_bytes()) {

     if (PrintAdaptiveSizePolicy && Verbose) {

       gclog_or_tty->print_cr("    capacities are the right sizes, returning");

     }

     return;

   }

   char* eden_start = (char*)eden_space()->bottom();

   char* eden_end   = (char*)eden_space()->end();

   char* from_start = (char*)from_space()->bottom();

   char* from_end   = (char*)from_space()->end();

   char* to_start   = (char*)to_space()->bottom();

   char* to_end     = (char*)to_space()->end();

   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();

   const size_t alignment = heap->space_alignment();

   const bool maintain_minimum =

     (requested_eden_size + 2 * requested_survivor_size) <= min_gen_size();

   bool eden_from_to_order = from_start < to_start;

   // Check whether from space is below to space

   if (eden_from_to_order) {

     // Eden, from, to

     eden_from_to_order = true;

     if (PrintAdaptiveSizePolicy && Verbose) {

       gclog_or_tty->print_cr("  Eden, from, to:");

     }

     // Set eden

     // "requested_eden_size" is a goal for the size of eden

     // and may not be attainable.  "eden_size" below is

     // calculated based on the location of from-space and

     // the goal for the size of eden.  from-space is

     // fixed in place because it contains live data.

     // The calculation is done this way to avoid 32bit

     // overflow (i.e., eden_start + requested_eden_size

     // may too large for representation in 32bits).

     size_t eden_size;

     if (maintain_minimum) {

       // Only make eden larger than the requested size if

       // the minimum size of the generation has to be maintained.

       // This could be done in general but policy at a higher

       // level is determining a requested size for eden and that

       // should be honored unless there is a fundamental reason.

       eden_size = pointer_delta(from_start,

                                 eden_start,

                                 sizeof(char));

     } else {

       eden_size = MIN2(requested_eden_size,

                        pointer_delta(from_start, eden_start, sizeof(char)));

     }

     eden_end = eden_start + eden_size;

     assert(eden_end >= eden_start, "addition overflowed");

     // To may resize into from space as long as it is clear of live data.

     // From space must remain page aligned, though, so we need to do some

     // extra calculations.

     // First calculate an optimal to-space

     to_end   = (char*)virtual_space()->high();

     to_start = (char*)pointer_delta(to_end, (char*)requested_survivor_size,

                                     sizeof(char));

     // Does the optimal to-space overlap from-space?

     if (to_start < (char*)from_space()->end()) {

       assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");

       // Calculate the minimum offset possible for from_end

       size_t from_size = pointer_delta(from_space()->top(), from_start, sizeof(char));

       // Should we be in this method if from_space is empty? Why not the set_space method? FIX ME!

       if (from_size == 0) {

         from_size = alignment;

       } else {

         from_size = align_size_up(from_size, alignment);

       }

       from_end = from_start + from_size;

       assert(from_end > from_start, "addition overflow or from_size problem");

       guarantee(from_end <= (char*)from_space()->end(), "from_end moved to the right");

       // Now update to_start with the new from_end

       to_start = MAX2(from_end, to_start);

     }

     guarantee(to_start != to_end, "to space is zero sized");

     if (PrintAdaptiveSizePolicy && Verbose) {

       gclog_or_tty->print_cr("    [eden_start .. eden_end): "

                     "[" PTR_FORMAT " .. " PTR_FORMAT ") " SIZE_FORMAT,

                     eden_start,

                     eden_end,

                     pointer_delta(eden_end, eden_start, sizeof(char)));

       gclog_or_tty->print_cr("    [from_start .. from_end): "

                     "[" PTR_FORMAT " .. " PTR_FORMAT ") " SIZE_FORMAT,

                     from_start,

                     from_end,

                     pointer_delta(from_end, from_start, sizeof(char)));

       gclog_or_tty->print_cr("    [  to_start ..   to_end): "

                     "[" PTR_FORMAT " .. " PTR_FORMAT ") " SIZE_FORMAT,

                     to_start,

                     to_end,

                     pointer_delta(  to_end,   to_start, sizeof(char)));

     }

   } else {

     // Eden, to, from

     if (PrintAdaptiveSizePolicy && Verbose) {

       gclog_or_tty->print_cr("  Eden, to, from:");

     }

     // To space gets priority over eden resizing. Note that we position

     // to space as if we were able to resize from space, even though from

     // space is not modified.

     // Giving eden priority was tried and gave poorer performance.

     to_end   = (char*)pointer_delta(virtual_space()->high(),

                                     (char*)requested_survivor_size,

                                     sizeof(char));

     to_end   = MIN2(to_end, from_start);

     to_start = (char*)pointer_delta(to_end, (char*)requested_survivor_size,

                                     sizeof(char));

     // if the space sizes are to be increased by several times then

     // 'to_start' will point beyond the young generation. In this case

     // 'to_start' should be adjusted.

     to_start = MAX2(to_start, eden_start + alignment);

     // Compute how big eden can be, then adjust end.

     // See  comments above on calculating eden_end.

     size_t eden_size;

     if (maintain_minimum) {

       eden_size = pointer_delta(to_start, eden_start, sizeof(char));

     } else {

       eden_size = MIN2(requested_eden_size,

                        pointer_delta(to_start, eden_start, sizeof(char)));

     }

     eden_end = eden_start + eden_size;

     assert(eden_end >= eden_start, "addition overflowed");

     // Could choose to not let eden shrink

     // to_start = MAX2(to_start, eden_end);

     // Don't let eden shrink down to 0 or less.

     eden_end = MAX2(eden_end, eden_start + alignment);

     to_start = MAX2(to_start, eden_end);

     if (PrintAdaptiveSizePolicy && Verbose) {

       gclog_or_tty->print_cr("    [eden_start .. eden_end): "

                     "[" PTR_FORMAT " .. " PTR_FORMAT ") " SIZE_FORMAT,

                     eden_start,

                     eden_end,

                     pointer_delta(eden_end, eden_start, sizeof(char)));

       gclog_or_tty->print_cr("    [  to_start ..   to_end): "

                     "[" PTR_FORMAT " .. " PTR_FORMAT ") " SIZE_FORMAT,

                     to_start,

                     to_end,

                     pointer_delta(  to_end,   to_start, sizeof(char)));

       gclog_or_tty->print_cr("    [from_start .. from_end): "

                     "[" PTR_FORMAT " .. " PTR_FORMAT ") " SIZE_FORMAT,

                     from_start,

                     from_end,

                     pointer_delta(from_end, from_start, sizeof(char)));

     }

   }

   guarantee((HeapWord*)from_start <= from_space()->bottom(),

             "from start moved to the right");

   guarantee((HeapWord*)from_end >= from_space()->top(),

             "from end moved into live data");

   assert(is_object_aligned((intptr_t)eden_start), "checking alignment");

   assert(is_object_aligned((intptr_t)from_start), "checking alignment");

   assert(is_object_aligned((intptr_t)to_start), "checking alignment");

   MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)eden_end);

   MemRegion toMR  ((HeapWord*)to_start,   (HeapWord*)to_end);

   MemRegion fromMR((HeapWord*)from_start, (HeapWord*)from_end);

   // Let's make sure the call to initialize doesn't reset "top"!

   HeapWord* old_from_top = from_space()->top();

   // For PrintAdaptiveSizePolicy block  below

   size_t old_from = from_space()->capacity_in_bytes();

   size_t old_to   = to_space()->capacity_in_bytes();

   if (ZapUnusedHeapArea) {

     // NUMA is a special case because a numa space is not mangled

     // in order to not prematurely bind its address to memory to

     // the wrong memory (i.e., don't want the GC thread to first

     // touch the memory).  The survivor spaces are not numa

     // spaces and are mangled.

     if (UseNUMA) {

       if (eden_from_to_order) {

         mangle_survivors(from_space(), fromMR, to_space(), toMR);

       } else {

         mangle_survivors(to_space(), toMR, from_space(), fromMR);

       }

     }

     // If not mangling the spaces, do some checking to verify that

     // the spaces are already mangled.

     // The spaces should be correctly mangled at this point so

     // do some checking here. Note that they are not being mangled

     // in the calls to initialize().

     // Must check mangling before the spaces are reshaped.  Otherwise,

     // the bottom or end of one space may have moved into an area

     // covered by another space and a failure of the check may

     // not correctly indicate which space is not properly mangled.

     HeapWord* limit = (HeapWord*) virtual_space()->high();

     eden_space()->check_mangled_unused_area(limit);

     from_space()->check_mangled_unused_area(limit);

       to_space()->check_mangled_unused_area(limit);

   }

   // When an existing space is being initialized, it is not

   // mangled because the space has been previously mangled.

   eden_space()->initialize(edenMR,

                            SpaceDecorator::Clear,

                            SpaceDecorator::DontMangle);

     to_space()->initialize(toMR,

                            SpaceDecorator::Clear,

                            SpaceDecorator::DontMangle);

   from_space()->initialize(fromMR,

                            SpaceDecorator::DontClear,

                            SpaceDecorator::DontMangle);

   assert(from_space()->top() == old_from_top, "from top changed!");

   if (PrintAdaptiveSizePolicy) {

     ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();

     assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");

     gclog_or_tty->print("AdaptiveSizePolicy::survivor space sizes: "

                   "collection: %d "

                   "(" SIZE_FORMAT ", " SIZE_FORMAT ") -> "

                   "(" SIZE_FORMAT ", " SIZE_FORMAT ") ",

                   heap->total_collections(),

                   old_from, old_to,

                   from_space()->capacity_in_bytes(),

                   to_space()->capacity_in_bytes());

     gclog_or_tty->cr();

   }

 }

 void PSYoungGen::swap_spaces() {

   MutableSpace* s    = from_space();

   _from_space        = to_space();

   _to_space          = s;

   // Now update the decorators.

   PSMarkSweepDecorator* md = from_mark_sweep();

   _from_mark_sweep           = to_mark_sweep();

   _to_mark_sweep             = md;

   assert(from_mark_sweep()->space() == from_space(), "Sanity");

   assert(to_mark_sweep()->space() == to_space(), "Sanity");

 }

 size_t PSYoungGen::capacity_in_bytes() const {

   return eden_space()->capacity_in_bytes()

        + from_space()->capacity_in_bytes();  // to_space() is only used during scavenge

 }

 size_t PSYoungGen::used_in_bytes() const {

   return eden_space()->used_in_bytes()

        + from_space()->used_in_bytes();      // to_space() is only used during scavenge

 }

 size_t PSYoungGen::free_in_bytes() const {

   return eden_space()->free_in_bytes()

        + from_space()->free_in_bytes();      // to_space() is only used during scavenge

 }

 size_t PSYoungGen::capacity_in_words() const {

   return eden_space()->capacity_in_words()

        + from_space()->capacity_in_words();  // to_space() is only used during scavenge

 }

 size_t PSYoungGen::used_in_words() const {

   return eden_space()->used_in_words()

        + from_space()->used_in_words();      // to_space() is only used during scavenge

 }

 size_t PSYoungGen::free_in_words() const {

   return eden_space()->free_in_words()

        + from_space()->free_in_words();      // to_space() is only used during scavenge

 }

 void PSYoungGen::object_iterate(ObjectClosure* blk) {

   eden_space()->object_iterate(blk);

   from_space()->object_iterate(blk);

   to_space()->object_iterate(blk);

 }

 void PSYoungGen::precompact() {

   eden_mark_sweep()->precompact();

   from_mark_sweep()->precompact();

   to_mark_sweep()->precompact();

 }

 void PSYoungGen::adjust_pointers() {

   eden_mark_sweep()->adjust_pointers();

   from_mark_sweep()->adjust_pointers();

   to_mark_sweep()->adjust_pointers();

 }

 void PSYoungGen::compact() {

   eden_mark_sweep()->compact(ZapUnusedHeapArea);

   from_mark_sweep()->compact(ZapUnusedHeapArea);

   // Mark sweep stores preserved markOops in to space, don't disturb!

   to_mark_sweep()->compact(false);

 }

 void PSYoungGen::print() const { print_on(tty); }

 void PSYoungGen::print_on(outputStream* st) const {

   st->print(" %-15s", "PSYoungGen");

   if (PrintGCDetails && Verbose) {

     st->print(" total " SIZE_FORMAT ", used " SIZE_FORMAT,

                capacity_in_bytes(), used_in_bytes());

   } else {

     st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",

                capacity_in_bytes()/K, used_in_bytes()/K);

   }

   virtual_space()->print_space_boundaries_on(st);

   st->print("  eden"); eden_space()->print_on(st);

   st->print("  from"); from_space()->print_on(st);

   st->print("  to  "); to_space()->print_on(st);

 }

 // Note that a space is not printed before the [NAME:

 void PSYoungGen::print_used_change(size_t prev_used) const {

   gclog_or_tty->print("[%s:", name());

   gclog_or_tty->print(" "  SIZE_FORMAT "K"

                       "->" SIZE_FORMAT "K"

                       "("  SIZE_FORMAT "K)",

                       prev_used / K, used_in_bytes() / K,

                       capacity_in_bytes() / K);

   gclog_or_tty->print("]");

 }

 size_t PSYoungGen::available_for_expansion() {

   ShouldNotReachHere();

   return 0;

 }

 size_t PSYoungGen::available_for_contraction() {

   ShouldNotReachHere();

   return 0;

 }

 size_t PSYoungGen::available_to_min_gen() {

   assert(virtual_space()->committed_size() >= min_gen_size(), "Invariant");

   return virtual_space()->committed_size() - min_gen_size();

 }

 // This method assumes that from-space has live data and that

 // any shrinkage of the young gen is limited by location of

 // from-space.

 size_t PSYoungGen::available_to_live() {

   size_t delta_in_survivor = 0;

   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();

   const size_t space_alignment = heap->space_alignment();

   const size_t gen_alignment = heap->generation_alignment();

   MutableSpace* space_shrinking = NULL;

   if (from_space()->end() > to_space()->end()) {

     space_shrinking = from_space();

   } else {

     space_shrinking = to_space();

   }

   // Include any space that is committed but not included in

   // the survivor spaces.

   assert(((HeapWord*)virtual_space()->high()) >= space_shrinking->end(),

     "Survivor space beyond high end");

   size_t unused_committed = pointer_delta(virtual_space()->high(),

     space_shrinking->end(), sizeof(char));

   if (space_shrinking->is_empty()) {

     // Don't let the space shrink to 0

     assert(space_shrinking->capacity_in_bytes() >= space_alignment,

       "Space is too small");

     delta_in_survivor = space_shrinking->capacity_in_bytes() - space_alignment;

   } else {

     delta_in_survivor = pointer_delta(space_shrinking->end(),

                                       space_shrinking->top(),

                                       sizeof(char));

   }

   size_t delta_in_bytes = unused_committed + delta_in_survivor;

   delta_in_bytes = align_size_down(delta_in_bytes, gen_alignment);

   return delta_in_bytes;

 }

 // Return the number of bytes available for resizing down the young

 // generation.  This is the minimum of

 //      input "bytes"

 //      bytes to the minimum young gen size

 //      bytes to the size currently being used + some small extra

 size_t PSYoungGen::limit_gen_shrink(size_t bytes) {

   // Allow shrinkage into the current eden but keep eden large enough

   // to maintain the minimum young gen size

   bytes = MIN3(bytes, available_to_min_gen(), available_to_live());

   return align_size_down(bytes, virtual_space()->alignment());

 }

 void PSYoungGen::reset_after_change() {

   ShouldNotReachHere();

 }

 void PSYoungGen::reset_survivors_after_shrink() {

   _reserved = MemRegion((HeapWord*)virtual_space()->low_boundary(),

                         (HeapWord*)virtual_space()->high_boundary());

   PSScavenge::reference_processor()->set_span(_reserved);

   MutableSpace* space_shrinking = NULL;

   if (from_space()->end() > to_space()->end()) {

     space_shrinking = from_space();

   } else {

     space_shrinking = to_space();

   }

   HeapWord* new_end = (HeapWord*)virtual_space()->high();

   assert(new_end >= space_shrinking->bottom(), "Shrink was too large");

   // Was there a shrink of the survivor space?

   if (new_end < space_shrinking->end()) {

     MemRegion mr(space_shrinking->bottom(), new_end);

     space_shrinking->initialize(mr,

                                 SpaceDecorator::DontClear,

                                 SpaceDecorator::Mangle);

   }

 }

 // This method currently does not expect to expand into eden (i.e.,

 // the virtual space boundaries is expected to be consistent

 // with the eden boundaries..

 void PSYoungGen::post_resize() {

   assert_locked_or_safepoint(Heap_lock);

   assert((eden_space()->bottom() < to_space()->bottom()) &&

          (eden_space()->bottom() < from_space()->bottom()),

          "Eden is assumed to be below the survivor spaces");

   MemRegion cmr((HeapWord*)virtual_space()->low(),

                 (HeapWord*)virtual_space()->high());

   Universe::heap()->barrier_set()->resize_covered_region(cmr);

   space_invariants();

 }

 void PSYoungGen::update_counters() {

   if (UsePerfData) {

     _eden_counters->update_all();

     _from_counters->update_all();

     _to_counters->update_all();

     _gen_counters->update_all();

   }

 }

 void PSYoungGen::verify() {

   eden_space()->verify();

   from_space()->verify();

   to_space()->verify();

 }

 #ifndef PRODUCT

 void PSYoungGen::record_spaces_top() {

   assert(ZapUnusedHeapArea, "Not mangling unused space");

   eden_space()->set_top_for_allocations();

   from_space()->set_top_for_allocations();

   to_space()->set_top_for_allocations();

 }

 #endif