1 /*
   2  * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "gc/parallel/mutableNUMASpace.hpp"
  27 #include "gc/parallel/parallelScavengeHeap.hpp"
  28 #include "gc/parallel/psMarkSweepDecorator.hpp"
  29 #include "gc/parallel/psScavenge.hpp"
  30 #include "gc/parallel/psYoungGen.hpp"
  31 #include "gc/shared/gcUtil.hpp"
  32 #include "gc/shared/spaceDecorator.hpp"
  33 #include "logging/log.hpp"
  34 #include "oops/oop.inline.hpp"
  35 #include "runtime/java.hpp"
  36 
  37 PSYoungGen::PSYoungGen(size_t        initial_size,
  38                        size_t        min_size,
  39                        size_t        max_size) :
  40   _init_gen_size(initial_size),
  41   _min_gen_size(min_size),
  42   _max_gen_size(max_size)
  43 {}
  44 
  45 void PSYoungGen::initialize_virtual_space(ReservedSpace rs, size_t alignment) {
  46   assert(_init_gen_size != 0, "Should have a finite size");
  47   _virtual_space = new PSVirtualSpace(rs, alignment);
  48   if (!virtual_space()->expand_by(_init_gen_size)) {
  49     vm_exit_during_initialization("Could not reserve enough space for "
  50                                   "object heap");
  51   }
  52 }
  53 
  54 void PSYoungGen::initialize(ReservedSpace rs, size_t alignment) {
  55   initialize_virtual_space(rs, alignment);
  56   initialize_work();
  57 }
  58 
  59 void PSYoungGen::initialize_work() {
  60 
  61   _reserved = MemRegion((HeapWord*)virtual_space()->low_boundary(),
  62                         (HeapWord*)virtual_space()->high_boundary());
  63 
  64   MemRegion cmr((HeapWord*)virtual_space()->low(),
  65                 (HeapWord*)virtual_space()->high());
  66   ParallelScavengeHeap::heap()->barrier_set()->resize_covered_region(cmr);
  67 
  68   if (ZapUnusedHeapArea) {
  69     // Mangle newly committed space immediately because it
  70     // can be done here more simply that after the new
  71     // spaces have been computed.
  72     SpaceMangler::mangle_region(cmr);
  73   }
  74 
  75   if (UseNUMA) {
  76     _eden_space = new MutableNUMASpace(virtual_space()->alignment());
  77   } else {
  78     _eden_space = new MutableSpace(virtual_space()->alignment());
  79   }
  80   _from_space = new MutableSpace(virtual_space()->alignment());
  81   _to_space   = new MutableSpace(virtual_space()->alignment());
  82 
  83   if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) {
  84     vm_exit_during_initialization("Could not allocate a young gen space");
  85   }
  86 
  87   // Allocate the mark sweep views of spaces
  88   _eden_mark_sweep =
  89       new PSMarkSweepDecorator(_eden_space, NULL, MarkSweepDeadRatio);
  90   _from_mark_sweep =
  91       new PSMarkSweepDecorator(_from_space, NULL, MarkSweepDeadRatio);
  92   _to_mark_sweep =
  93       new PSMarkSweepDecorator(_to_space, NULL, MarkSweepDeadRatio);
  94 
  95   if (_eden_mark_sweep == NULL ||
  96       _from_mark_sweep == NULL ||
  97       _to_mark_sweep == NULL) {
  98     vm_exit_during_initialization("Could not complete allocation"
  99                                   " of the young generation");
 100   }
 101 
 102   // Generation Counters - generation 0, 3 subspaces
 103   _gen_counters = new PSGenerationCounters("new", 0, 3, _min_gen_size,
 104                                            _max_gen_size, _virtual_space);
 105 
 106   // Compute maximum space sizes for performance counters
 107   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 108   size_t alignment = heap->space_alignment();
 109   size_t size = virtual_space()->reserved_size();
 110 
 111   size_t max_survivor_size;
 112   size_t max_eden_size;
 113 
 114   if (UseAdaptiveSizePolicy) {
 115     max_survivor_size = size / MinSurvivorRatio;
 116 
 117     // round the survivor space size down to the nearest alignment
 118     // and make sure its size is greater than 0.
 119     max_survivor_size = align_size_down(max_survivor_size, alignment);
 120     max_survivor_size = MAX2(max_survivor_size, alignment);
 121 
 122     // set the maximum size of eden to be the size of the young gen
 123     // less two times the minimum survivor size. The minimum survivor
 124     // size for UseAdaptiveSizePolicy is one alignment.
 125     max_eden_size = size - 2 * alignment;
 126   } else {
 127     max_survivor_size = size / InitialSurvivorRatio;
 128 
 129     // round the survivor space size down to the nearest alignment
 130     // and make sure its size is greater than 0.
 131     max_survivor_size = align_size_down(max_survivor_size, alignment);
 132     max_survivor_size = MAX2(max_survivor_size, alignment);
 133 
 134     // set the maximum size of eden to be the size of the young gen
 135     // less two times the survivor size when the generation is 100%
 136     // committed. The minimum survivor size for -UseAdaptiveSizePolicy
 137     // is dependent on the committed portion (current capacity) of the
 138     // generation - the less space committed, the smaller the survivor
 139     // space, possibly as small as an alignment. However, we are interested
 140     // in the case where the young generation is 100% committed, as this
 141     // is the point where eden reaches its maximum size. At this point,
 142     // the size of a survivor space is max_survivor_size.
 143     max_eden_size = size - 2 * max_survivor_size;
 144   }
 145 
 146   _eden_counters = new SpaceCounters("eden", 0, max_eden_size, _eden_space,
 147                                      _gen_counters);
 148   _from_counters = new SpaceCounters("s0", 1, max_survivor_size, _from_space,
 149                                      _gen_counters);
 150   _to_counters = new SpaceCounters("s1", 2, max_survivor_size, _to_space,
 151                                    _gen_counters);
 152 
 153   compute_initial_space_boundaries();
 154 }
 155 
 156 void PSYoungGen::compute_initial_space_boundaries() {
 157   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 158 
 159   // Compute sizes
 160   size_t alignment = heap->space_alignment();
 161   size_t size = virtual_space()->committed_size();
 162   assert(size >= 3 * alignment, "Young space is not large enough for eden + 2 survivors");
 163 
 164   size_t survivor_size = size / InitialSurvivorRatio;
 165   survivor_size = align_size_down(survivor_size, alignment);
 166   // ... but never less than an alignment
 167   survivor_size = MAX2(survivor_size, alignment);
 168 
 169   // Young generation is eden + 2 survivor spaces
 170   size_t eden_size = size - (2 * survivor_size);
 171 
 172   // Now go ahead and set 'em.
 173   set_space_boundaries(eden_size, survivor_size);
 174   space_invariants();
 175 
 176   if (UsePerfData) {
 177     _eden_counters->update_capacity();
 178     _from_counters->update_capacity();
 179     _to_counters->update_capacity();
 180   }
 181 }
 182 
 183 void PSYoungGen::set_space_boundaries(size_t eden_size, size_t survivor_size) {
 184   assert(eden_size < virtual_space()->committed_size(), "just checking");
 185   assert(eden_size > 0  && survivor_size > 0, "just checking");
 186 
 187   // Initial layout is Eden, to, from. After swapping survivor spaces,
 188   // that leaves us with Eden, from, to, which is step one in our two
 189   // step resize-with-live-data procedure.
 190   char *eden_start = virtual_space()->low();
 191   char *to_start   = eden_start + eden_size;
 192   char *from_start = to_start   + survivor_size;
 193   char *from_end   = from_start + survivor_size;
 194 
 195   assert(from_end == virtual_space()->high(), "just checking");
 196   assert(is_object_aligned((intptr_t)eden_start), "checking alignment");
 197   assert(is_object_aligned((intptr_t)to_start),   "checking alignment");
 198   assert(is_object_aligned((intptr_t)from_start), "checking alignment");
 199 
 200   MemRegion eden_mr((HeapWord*)eden_start, (HeapWord*)to_start);
 201   MemRegion to_mr  ((HeapWord*)to_start, (HeapWord*)from_start);
 202   MemRegion from_mr((HeapWord*)from_start, (HeapWord*)from_end);
 203 
 204   eden_space()->initialize(eden_mr, true, ZapUnusedHeapArea);
 205     to_space()->initialize(to_mr  , true, ZapUnusedHeapArea);
 206   from_space()->initialize(from_mr, true, ZapUnusedHeapArea);
 207 }
 208 
 209 #ifndef PRODUCT
 210 void PSYoungGen::space_invariants() {
 211   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 212   const size_t alignment = heap->space_alignment();
 213 
 214   // Currently, our eden size cannot shrink to zero
 215   guarantee(eden_space()->capacity_in_bytes() >= alignment, "eden too small");
 216   guarantee(from_space()->capacity_in_bytes() >= alignment, "from too small");
 217   guarantee(to_space()->capacity_in_bytes() >= alignment, "to too small");
 218 
 219   // Relationship of spaces to each other
 220   char* eden_start = (char*)eden_space()->bottom();
 221   char* eden_end   = (char*)eden_space()->end();
 222   char* from_start = (char*)from_space()->bottom();
 223   char* from_end   = (char*)from_space()->end();
 224   char* to_start   = (char*)to_space()->bottom();
 225   char* to_end     = (char*)to_space()->end();
 226 
 227   guarantee(eden_start >= virtual_space()->low(), "eden bottom");
 228   guarantee(eden_start < eden_end, "eden space consistency");
 229   guarantee(from_start < from_end, "from space consistency");
 230   guarantee(to_start < to_end, "to space consistency");
 231 
 232   // Check whether from space is below to space
 233   if (from_start < to_start) {
 234     // Eden, from, to
 235     guarantee(eden_end <= from_start, "eden/from boundary");
 236     guarantee(from_end <= to_start,   "from/to boundary");
 237     guarantee(to_end <= virtual_space()->high(), "to end");
 238   } else {
 239     // Eden, to, from
 240     guarantee(eden_end <= to_start, "eden/to boundary");
 241     guarantee(to_end <= from_start, "to/from boundary");
 242     guarantee(from_end <= virtual_space()->high(), "from end");
 243   }
 244 
 245   // More checks that the virtual space is consistent with the spaces
 246   assert(virtual_space()->committed_size() >=
 247     (eden_space()->capacity_in_bytes() +
 248      to_space()->capacity_in_bytes() +
 249      from_space()->capacity_in_bytes()), "Committed size is inconsistent");
 250   assert(virtual_space()->committed_size() <= virtual_space()->reserved_size(),
 251     "Space invariant");
 252   char* eden_top = (char*)eden_space()->top();
 253   char* from_top = (char*)from_space()->top();
 254   char* to_top = (char*)to_space()->top();
 255   assert(eden_top <= virtual_space()->high(), "eden top");
 256   assert(from_top <= virtual_space()->high(), "from top");
 257   assert(to_top <= virtual_space()->high(), "to top");
 258 
 259   virtual_space()->verify();
 260 }
 261 #endif
 262 
 263 void PSYoungGen::resize(size_t eden_size, size_t survivor_size) {
 264   // Resize the generation if needed. If the generation resize
 265   // reports false, do not attempt to resize the spaces.
 266   if (resize_generation(eden_size, survivor_size)) {
 267     // Then we lay out the spaces inside the generation
 268     resize_spaces(eden_size, survivor_size);
 269 
 270     space_invariants();
 271 
 272     log_trace(gc, ergo)("Young generation size: "
 273                         "desired eden: " SIZE_FORMAT " survivor: " SIZE_FORMAT
 274                         " used: " SIZE_FORMAT " capacity: " SIZE_FORMAT
 275                         " gen limits: " SIZE_FORMAT " / " SIZE_FORMAT,
 276                         eden_size, survivor_size, used_in_bytes(), capacity_in_bytes(),
 277                         _max_gen_size, min_gen_size());
 278   }
 279 }
 280 
 281 
 282 bool PSYoungGen::resize_generation(size_t eden_size, size_t survivor_size) {
 283   const size_t alignment = virtual_space()->alignment();
 284   size_t orig_size = virtual_space()->committed_size();
 285   bool size_changed = false;
 286 
 287   // There used to be this guarantee there.
 288   // guarantee ((eden_size + 2*survivor_size)  <= _max_gen_size, "incorrect input arguments");
 289   // Code below forces this requirement.  In addition the desired eden
 290   // size and desired survivor sizes are desired goals and may
 291   // exceed the total generation size.
 292 
 293   assert(min_gen_size() <= orig_size && orig_size <= max_size(), "just checking");
 294 
 295   // Adjust new generation size
 296   const size_t eden_plus_survivors =
 297           align_size_up(eden_size + 2 * survivor_size, alignment);
 298   size_t desired_size = MAX2(MIN2(eden_plus_survivors, max_size()),
 299                              min_gen_size());
 300   assert(desired_size <= max_size(), "just checking");
 301 
 302   if (desired_size > orig_size) {
 303     // Grow the generation
 304     size_t change = desired_size - orig_size;
 305     assert(change % alignment == 0, "just checking");
 306     HeapWord* prev_high = (HeapWord*) virtual_space()->high();
 307     if (!virtual_space()->expand_by(change)) {
 308       return false; // Error if we fail to resize!
 309     }
 310     if (ZapUnusedHeapArea) {
 311       // Mangle newly committed space immediately because it
 312       // can be done here more simply that after the new
 313       // spaces have been computed.
 314       HeapWord* new_high = (HeapWord*) virtual_space()->high();
 315       MemRegion mangle_region(prev_high, new_high);
 316       SpaceMangler::mangle_region(mangle_region);
 317     }
 318     size_changed = true;
 319   } else if (desired_size < orig_size) {
 320     size_t desired_change = orig_size - desired_size;
 321     assert(desired_change % alignment == 0, "just checking");
 322 
 323     desired_change = limit_gen_shrink(desired_change);
 324 
 325     if (desired_change > 0) {
 326       virtual_space()->shrink_by(desired_change);
 327       reset_survivors_after_shrink();
 328 
 329       size_changed = true;
 330     }
 331   } else {
 332     if (orig_size == gen_size_limit()) {
 333       log_trace(gc)("PSYoung generation size at maximum: " SIZE_FORMAT "K", orig_size/K);
 334     } else if (orig_size == min_gen_size()) {
 335       log_trace(gc)("PSYoung generation size at minium: " SIZE_FORMAT "K", orig_size/K);
 336     }
 337   }
 338 
 339   if (size_changed) {
 340     post_resize();
 341     log_trace(gc)("PSYoung generation size changed: " SIZE_FORMAT "K->" SIZE_FORMAT "K",
 342                   orig_size/K, virtual_space()->committed_size()/K);
 343   }
 344 
 345   guarantee(eden_plus_survivors <= virtual_space()->committed_size() ||
 346             virtual_space()->committed_size() == max_size(), "Sanity");
 347 
 348   return true;
 349 }
 350 
 351 #ifndef PRODUCT
 352 // In the numa case eden is not mangled so a survivor space
 353 // moving into a region previously occupied by a survivor
 354 // may find an unmangled region.  Also in the PS case eden
 355 // to-space and from-space may not touch (i.e., there may be
 356 // gaps between them due to movement while resizing the
 357 // spaces).  Those gaps must be mangled.
 358 void PSYoungGen::mangle_survivors(MutableSpace* s1,
 359                                   MemRegion s1MR,
 360                                   MutableSpace* s2,
 361                                   MemRegion s2MR) {
 362   // Check eden and gap between eden and from-space, in deciding
 363   // what to mangle in from-space.  Check the gap between from-space
 364   // and to-space when deciding what to mangle.
 365   //
 366   //      +--------+   +----+    +---+
 367   //      | eden   |   |s1  |    |s2 |
 368   //      +--------+   +----+    +---+
 369   //                 +-------+ +-----+
 370   //                 |s1MR   | |s2MR |
 371   //                 +-------+ +-----+
 372   // All of survivor-space is properly mangled so find the
 373   // upper bound on the mangling for any portion above current s1.
 374   HeapWord* delta_end = MIN2(s1->bottom(), s1MR.end());
 375   MemRegion delta1_left;
 376   if (s1MR.start() < delta_end) {
 377     delta1_left = MemRegion(s1MR.start(), delta_end);
 378     s1->mangle_region(delta1_left);
 379   }
 380   // Find any portion to the right of the current s1.
 381   HeapWord* delta_start = MAX2(s1->end(), s1MR.start());
 382   MemRegion delta1_right;
 383   if (delta_start < s1MR.end()) {
 384     delta1_right = MemRegion(delta_start, s1MR.end());
 385     s1->mangle_region(delta1_right);
 386   }
 387 
 388   // Similarly for the second survivor space except that
 389   // any of the new region that overlaps with the current
 390   // region of the first survivor space has already been
 391   // mangled.
 392   delta_end = MIN2(s2->bottom(), s2MR.end());
 393   delta_start = MAX2(s2MR.start(), s1->end());
 394   MemRegion delta2_left;
 395   if (s2MR.start() < delta_end) {
 396     delta2_left = MemRegion(s2MR.start(), delta_end);
 397     s2->mangle_region(delta2_left);
 398   }
 399   delta_start = MAX2(s2->end(), s2MR.start());
 400   MemRegion delta2_right;
 401   if (delta_start < s2MR.end()) {
 402     s2->mangle_region(delta2_right);
 403   }
 404 
 405   // s1
 406   log_develop(gc)("Current region: [" PTR_FORMAT ", " PTR_FORMAT ") "
 407     "New region: [" PTR_FORMAT ", " PTR_FORMAT ")",
 408     p2i(s1->bottom()), p2i(s1->end()),
 409     p2i(s1MR.start()), p2i(s1MR.end()));
 410   log_develop(gc)("    Mangle before: [" PTR_FORMAT ", "
 411     PTR_FORMAT ")  Mangle after: [" PTR_FORMAT ", " PTR_FORMAT ")",
 412     p2i(delta1_left.start()), p2i(delta1_left.end()),
 413     p2i(delta1_right.start()), p2i(delta1_right.end()));
 414 
 415   // s2
 416   log_develop(gc)("Current region: [" PTR_FORMAT ", " PTR_FORMAT ") "
 417     "New region: [" PTR_FORMAT ", " PTR_FORMAT ")",
 418     p2i(s2->bottom()), p2i(s2->end()),
 419     p2i(s2MR.start()), p2i(s2MR.end()));
 420   log_develop(gc)("    Mangle before: [" PTR_FORMAT ", "
 421     PTR_FORMAT ")  Mangle after: [" PTR_FORMAT ", " PTR_FORMAT ")",
 422     p2i(delta2_left.start()), p2i(delta2_left.end()),
 423     p2i(delta2_right.start()), p2i(delta2_right.end()));
 424 }
 425 #endif // NOT PRODUCT
 426 
 427 void PSYoungGen::resize_spaces(size_t requested_eden_size,
 428                                size_t requested_survivor_size) {
 429   assert(UseAdaptiveSizePolicy, "sanity check");
 430   assert(requested_eden_size > 0  && requested_survivor_size > 0,
 431          "just checking");
 432 
 433   // We require eden and to space to be empty
 434   if ((!eden_space()->is_empty()) || (!to_space()->is_empty())) {
 435     return;
 436   }
 437 
 438   log_trace(gc, ergo)("PSYoungGen::resize_spaces(requested_eden_size: " SIZE_FORMAT ", requested_survivor_size: " SIZE_FORMAT ")",
 439                       requested_eden_size, requested_survivor_size);
 440   log_trace(gc, ergo)("    eden: [" PTR_FORMAT ".." PTR_FORMAT ") " SIZE_FORMAT,
 441                       p2i(eden_space()->bottom()),
 442                       p2i(eden_space()->end()),
 443                       pointer_delta(eden_space()->end(),
 444                                     eden_space()->bottom(),
 445                                     sizeof(char)));
 446   log_trace(gc, ergo)("    from: [" PTR_FORMAT ".." PTR_FORMAT ") " SIZE_FORMAT,
 447                       p2i(from_space()->bottom()),
 448                       p2i(from_space()->end()),
 449                       pointer_delta(from_space()->end(),
 450                                     from_space()->bottom(),
 451                                     sizeof(char)));
 452   log_trace(gc, ergo)("      to: [" PTR_FORMAT ".." PTR_FORMAT ") " SIZE_FORMAT,
 453                       p2i(to_space()->bottom()),
 454                       p2i(to_space()->end()),
 455                       pointer_delta(  to_space()->end(),
 456                                       to_space()->bottom(),
 457                                       sizeof(char)));
 458 
 459   // There's nothing to do if the new sizes are the same as the current
 460   if (requested_survivor_size == to_space()->capacity_in_bytes() &&
 461       requested_survivor_size == from_space()->capacity_in_bytes() &&
 462       requested_eden_size == eden_space()->capacity_in_bytes()) {
 463     log_trace(gc, ergo)("    capacities are the right sizes, returning");
 464     return;
 465   }
 466 
 467   char* eden_start = (char*)eden_space()->bottom();
 468   char* eden_end   = (char*)eden_space()->end();
 469   char* from_start = (char*)from_space()->bottom();
 470   char* from_end   = (char*)from_space()->end();
 471   char* to_start   = (char*)to_space()->bottom();
 472   char* to_end     = (char*)to_space()->end();
 473 
 474   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 475   const size_t alignment = heap->space_alignment();
 476   const bool maintain_minimum =
 477     (requested_eden_size + 2 * requested_survivor_size) <= min_gen_size();
 478 
 479   bool eden_from_to_order = from_start < to_start;
 480   // Check whether from space is below to space
 481   if (eden_from_to_order) {
 482     // Eden, from, to
 483     eden_from_to_order = true;
 484     log_trace(gc, ergo)("  Eden, from, to:");
 485 
 486     // Set eden
 487     // "requested_eden_size" is a goal for the size of eden
 488     // and may not be attainable.  "eden_size" below is
 489     // calculated based on the location of from-space and
 490     // the goal for the size of eden.  from-space is
 491     // fixed in place because it contains live data.
 492     // The calculation is done this way to avoid 32bit
 493     // overflow (i.e., eden_start + requested_eden_size
 494     // may too large for representation in 32bits).
 495     size_t eden_size;
 496     if (maintain_minimum) {
 497       // Only make eden larger than the requested size if
 498       // the minimum size of the generation has to be maintained.
 499       // This could be done in general but policy at a higher
 500       // level is determining a requested size for eden and that
 501       // should be honored unless there is a fundamental reason.
 502       eden_size = pointer_delta(from_start,
 503                                 eden_start,
 504                                 sizeof(char));
 505     } else {
 506       eden_size = MIN2(requested_eden_size,
 507                        pointer_delta(from_start, eden_start, sizeof(char)));
 508     }
 509 
 510     eden_end = eden_start + eden_size;
 511     assert(eden_end >= eden_start, "addition overflowed");
 512 
 513     // To may resize into from space as long as it is clear of live data.
 514     // From space must remain page aligned, though, so we need to do some
 515     // extra calculations.
 516 
 517     // First calculate an optimal to-space
 518     to_end   = (char*)virtual_space()->high();
 519     to_start = (char*)pointer_delta(to_end, (char*)requested_survivor_size,
 520                                     sizeof(char));
 521 
 522     // Does the optimal to-space overlap from-space?
 523     if (to_start < (char*)from_space()->end()) {
 524       // Calculate the minimum offset possible for from_end
 525       size_t from_size = pointer_delta(from_space()->top(), from_start, sizeof(char));
 526 
 527       // Should we be in this method if from_space is empty? Why not the set_space method? FIX ME!
 528       if (from_size == 0) {
 529         from_size = alignment;
 530       } else {
 531         from_size = align_size_up(from_size, alignment);
 532       }
 533 
 534       from_end = from_start + from_size;
 535       assert(from_end > from_start, "addition overflow or from_size problem");
 536 
 537       guarantee(from_end <= (char*)from_space()->end(), "from_end moved to the right");
 538 
 539       // Now update to_start with the new from_end
 540       to_start = MAX2(from_end, to_start);
 541     }
 542 
 543     guarantee(to_start != to_end, "to space is zero sized");
 544 
 545     log_trace(gc, ergo)("    [eden_start .. eden_end): [" PTR_FORMAT " .. " PTR_FORMAT ") " SIZE_FORMAT,
 546                         p2i(eden_start),
 547                         p2i(eden_end),
 548                         pointer_delta(eden_end, eden_start, sizeof(char)));
 549     log_trace(gc, ergo)("    [from_start .. from_end): [" PTR_FORMAT " .. " PTR_FORMAT ") " SIZE_FORMAT,
 550                         p2i(from_start),
 551                         p2i(from_end),
 552                         pointer_delta(from_end, from_start, sizeof(char)));
 553     log_trace(gc, ergo)("    [  to_start ..   to_end): [" PTR_FORMAT " .. " PTR_FORMAT ") " SIZE_FORMAT,
 554                         p2i(to_start),
 555                         p2i(to_end),
 556                         pointer_delta(  to_end,   to_start, sizeof(char)));
 557   } else {
 558     // Eden, to, from
 559     log_trace(gc, ergo)("  Eden, to, from:");
 560 
 561     // To space gets priority over eden resizing. Note that we position
 562     // to space as if we were able to resize from space, even though from
 563     // space is not modified.
 564     // Giving eden priority was tried and gave poorer performance.
 565     to_end   = (char*)pointer_delta(virtual_space()->high(),
 566                                     (char*)requested_survivor_size,
 567                                     sizeof(char));
 568     to_end   = MIN2(to_end, from_start);
 569     to_start = (char*)pointer_delta(to_end, (char*)requested_survivor_size,
 570                                     sizeof(char));
 571     // if the space sizes are to be increased by several times then
 572     // 'to_start' will point beyond the young generation. In this case
 573     // 'to_start' should be adjusted.
 574     to_start = MAX2(to_start, eden_start + alignment);
 575 
 576     // Compute how big eden can be, then adjust end.
 577     // See  comments above on calculating eden_end.
 578     size_t eden_size;
 579     if (maintain_minimum) {
 580       eden_size = pointer_delta(to_start, eden_start, sizeof(char));
 581     } else {
 582       eden_size = MIN2(requested_eden_size,
 583                        pointer_delta(to_start, eden_start, sizeof(char)));
 584     }
 585     eden_end = eden_start + eden_size;
 586     assert(eden_end >= eden_start, "addition overflowed");
 587 
 588     // Could choose to not let eden shrink
 589     // to_start = MAX2(to_start, eden_end);
 590 
 591     // Don't let eden shrink down to 0 or less.
 592     eden_end = MAX2(eden_end, eden_start + alignment);
 593     to_start = MAX2(to_start, eden_end);
 594 
 595     log_trace(gc, ergo)("    [eden_start .. eden_end): [" PTR_FORMAT " .. " PTR_FORMAT ") " SIZE_FORMAT,
 596                         p2i(eden_start),
 597                         p2i(eden_end),
 598                         pointer_delta(eden_end, eden_start, sizeof(char)));
 599     log_trace(gc, ergo)("    [  to_start ..   to_end): [" PTR_FORMAT " .. " PTR_FORMAT ") " SIZE_FORMAT,
 600                         p2i(to_start),
 601                         p2i(to_end),
 602                         pointer_delta(  to_end,   to_start, sizeof(char)));
 603     log_trace(gc, ergo)("    [from_start .. from_end): [" PTR_FORMAT " .. " PTR_FORMAT ") " SIZE_FORMAT,
 604                         p2i(from_start),
 605                         p2i(from_end),
 606                         pointer_delta(from_end, from_start, sizeof(char)));
 607   }
 608 
 609 
 610   guarantee((HeapWord*)from_start <= from_space()->bottom(),
 611             "from start moved to the right");
 612   guarantee((HeapWord*)from_end >= from_space()->top(),
 613             "from end moved into live data");
 614   assert(is_object_aligned((intptr_t)eden_start), "checking alignment");
 615   assert(is_object_aligned((intptr_t)from_start), "checking alignment");
 616   assert(is_object_aligned((intptr_t)to_start), "checking alignment");
 617 
 618   MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)eden_end);
 619   MemRegion toMR  ((HeapWord*)to_start,   (HeapWord*)to_end);
 620   MemRegion fromMR((HeapWord*)from_start, (HeapWord*)from_end);
 621 
 622   // Let's make sure the call to initialize doesn't reset "top"!
 623   HeapWord* old_from_top = from_space()->top();
 624 
 625   // For logging block  below
 626   size_t old_from = from_space()->capacity_in_bytes();
 627   size_t old_to   = to_space()->capacity_in_bytes();
 628 
 629   if (ZapUnusedHeapArea) {
 630     // NUMA is a special case because a numa space is not mangled
 631     // in order to not prematurely bind its address to memory to
 632     // the wrong memory (i.e., don't want the GC thread to first
 633     // touch the memory).  The survivor spaces are not numa
 634     // spaces and are mangled.
 635     if (UseNUMA) {
 636       if (eden_from_to_order) {
 637         mangle_survivors(from_space(), fromMR, to_space(), toMR);
 638       } else {
 639         mangle_survivors(to_space(), toMR, from_space(), fromMR);
 640       }
 641     }
 642 
 643     // If not mangling the spaces, do some checking to verify that
 644     // the spaces are already mangled.
 645     // The spaces should be correctly mangled at this point so
 646     // do some checking here. Note that they are not being mangled
 647     // in the calls to initialize().
 648     // Must check mangling before the spaces are reshaped.  Otherwise,
 649     // the bottom or end of one space may have moved into an area
 650     // covered by another space and a failure of the check may
 651     // not correctly indicate which space is not properly mangled.
 652     HeapWord* limit = (HeapWord*) virtual_space()->high();
 653     eden_space()->check_mangled_unused_area(limit);
 654     from_space()->check_mangled_unused_area(limit);
 655       to_space()->check_mangled_unused_area(limit);
 656   }
 657   // When an existing space is being initialized, it is not
 658   // mangled because the space has been previously mangled.
 659   eden_space()->initialize(edenMR,
 660                            SpaceDecorator::Clear,
 661                            SpaceDecorator::DontMangle);
 662     to_space()->initialize(toMR,
 663                            SpaceDecorator::Clear,
 664                            SpaceDecorator::DontMangle);
 665   from_space()->initialize(fromMR,
 666                            SpaceDecorator::DontClear,
 667                            SpaceDecorator::DontMangle);
 668 
 669   assert(from_space()->top() == old_from_top, "from top changed!");
 670 
 671   log_trace(gc, ergo)("AdaptiveSizePolicy::survivor space sizes: collection: %d (" SIZE_FORMAT ", " SIZE_FORMAT ") -> (" SIZE_FORMAT ", " SIZE_FORMAT ") ",
 672                       ParallelScavengeHeap::heap()->total_collections(),
 673                       old_from, old_to,
 674                       from_space()->capacity_in_bytes(),
 675                       to_space()->capacity_in_bytes());
 676 }
 677 
 678 void PSYoungGen::swap_spaces() {
 679   MutableSpace* s    = from_space();
 680   _from_space        = to_space();
 681   _to_space          = s;
 682 
 683   // Now update the decorators.
 684   PSMarkSweepDecorator* md = from_mark_sweep();
 685   _from_mark_sweep           = to_mark_sweep();
 686   _to_mark_sweep             = md;
 687 
 688   assert(from_mark_sweep()->space() == from_space(), "Sanity");
 689   assert(to_mark_sweep()->space() == to_space(), "Sanity");
 690 }
 691 
 692 size_t PSYoungGen::capacity_in_bytes() const {
 693   return eden_space()->capacity_in_bytes()
 694        + from_space()->capacity_in_bytes();  // to_space() is only used during scavenge
 695 }
 696 
 697 
 698 size_t PSYoungGen::used_in_bytes() const {
 699   return eden_space()->used_in_bytes()
 700        + from_space()->used_in_bytes();      // to_space() is only used during scavenge
 701 }
 702 
 703 
 704 size_t PSYoungGen::free_in_bytes() const {
 705   return eden_space()->free_in_bytes()
 706        + from_space()->free_in_bytes();      // to_space() is only used during scavenge
 707 }
 708 
 709 size_t PSYoungGen::capacity_in_words() const {
 710   return eden_space()->capacity_in_words()
 711        + from_space()->capacity_in_words();  // to_space() is only used during scavenge
 712 }
 713 
 714 
 715 size_t PSYoungGen::used_in_words() const {
 716   return eden_space()->used_in_words()
 717        + from_space()->used_in_words();      // to_space() is only used during scavenge
 718 }
 719 
 720 
 721 size_t PSYoungGen::free_in_words() const {
 722   return eden_space()->free_in_words()
 723        + from_space()->free_in_words();      // to_space() is only used during scavenge
 724 }
 725 
 726 void PSYoungGen::object_iterate(ObjectClosure* blk) {
 727   eden_space()->object_iterate(blk);
 728   from_space()->object_iterate(blk);
 729   to_space()->object_iterate(blk);
 730 }
 731 
 732 void PSYoungGen::precompact() {
 733   eden_mark_sweep()->precompact();
 734   from_mark_sweep()->precompact();
 735   to_mark_sweep()->precompact();
 736 }
 737 
 738 void PSYoungGen::adjust_pointers() {
 739   eden_mark_sweep()->adjust_pointers();
 740   from_mark_sweep()->adjust_pointers();
 741   to_mark_sweep()->adjust_pointers();
 742 }
 743 
 744 void PSYoungGen::compact() {
 745   eden_mark_sweep()->compact(ZapUnusedHeapArea);
 746   from_mark_sweep()->compact(ZapUnusedHeapArea);
 747   // Mark sweep stores preserved markOops in to space, don't disturb!
 748   to_mark_sweep()->compact(false);
 749 }
 750 
 751 void PSYoungGen::print() const { print_on(tty); }
 752 void PSYoungGen::print_on(outputStream* st) const {
 753   st->print(" %-15s", "PSYoungGen");
 754   if (PrintGCDetails && Verbose) {
 755     st->print(" total " SIZE_FORMAT ", used " SIZE_FORMAT,
 756                capacity_in_bytes(), used_in_bytes());
 757   } else {
 758     st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
 759                capacity_in_bytes()/K, used_in_bytes()/K);
 760   }
 761   virtual_space()->print_space_boundaries_on(st);
 762   st->print("  eden"); eden_space()->print_on(st);
 763   st->print("  from"); from_space()->print_on(st);
 764   st->print("  to  "); to_space()->print_on(st);
 765 }
 766 
 767 // Note that a space is not printed before the [NAME:
 768 void PSYoungGen::print_used_change(size_t prev_used) const {
 769   log_info(gc, heap)("%s: "  SIZE_FORMAT "K->" SIZE_FORMAT "K("  SIZE_FORMAT "K)",
 770       name(), prev_used / K, used_in_bytes() / K, capacity_in_bytes() / K);
 771 }
 772 
 773 size_t PSYoungGen::available_for_expansion() {
 774   ShouldNotReachHere();
 775   return 0;
 776 }
 777 
 778 size_t PSYoungGen::available_for_contraction() {
 779   ShouldNotReachHere();
 780   return 0;
 781 }
 782 
 783 size_t PSYoungGen::available_to_min_gen() {
 784   assert(virtual_space()->committed_size() >= min_gen_size(), "Invariant");
 785   return virtual_space()->committed_size() - min_gen_size();
 786 }
 787 
 788 // This method assumes that from-space has live data and that
 789 // any shrinkage of the young gen is limited by location of
 790 // from-space.
 791 size_t PSYoungGen::available_to_live() {
 792   size_t delta_in_survivor = 0;
 793   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 794   const size_t space_alignment = heap->space_alignment();
 795   const size_t gen_alignment = heap->generation_alignment();
 796 
 797   MutableSpace* space_shrinking = NULL;
 798   if (from_space()->end() > to_space()->end()) {
 799     space_shrinking = from_space();
 800   } else {
 801     space_shrinking = to_space();
 802   }
 803 
 804   // Include any space that is committed but not included in
 805   // the survivor spaces.
 806   assert(((HeapWord*)virtual_space()->high()) >= space_shrinking->end(),
 807     "Survivor space beyond high end");
 808   size_t unused_committed = pointer_delta(virtual_space()->high(),
 809     space_shrinking->end(), sizeof(char));
 810 
 811   if (space_shrinking->is_empty()) {
 812     // Don't let the space shrink to 0
 813     assert(space_shrinking->capacity_in_bytes() >= space_alignment,
 814       "Space is too small");
 815     delta_in_survivor = space_shrinking->capacity_in_bytes() - space_alignment;
 816   } else {
 817     delta_in_survivor = pointer_delta(space_shrinking->end(),
 818                                       space_shrinking->top(),
 819                                       sizeof(char));
 820   }
 821 
 822   size_t delta_in_bytes = unused_committed + delta_in_survivor;
 823   delta_in_bytes = align_size_down(delta_in_bytes, gen_alignment);
 824   return delta_in_bytes;
 825 }
 826 
 827 // Return the number of bytes available for resizing down the young
 828 // generation.  This is the minimum of
 829 //      input "bytes"
 830 //      bytes to the minimum young gen size
 831 //      bytes to the size currently being used + some small extra
 832 size_t PSYoungGen::limit_gen_shrink(size_t bytes) {
 833   // Allow shrinkage into the current eden but keep eden large enough
 834   // to maintain the minimum young gen size
 835   bytes = MIN3(bytes, available_to_min_gen(), available_to_live());
 836   return align_size_down(bytes, virtual_space()->alignment());
 837 }
 838 
 839 void PSYoungGen::reset_after_change() {
 840   ShouldNotReachHere();
 841 }
 842 
 843 void PSYoungGen::reset_survivors_after_shrink() {
 844   _reserved = MemRegion((HeapWord*)virtual_space()->low_boundary(),
 845                         (HeapWord*)virtual_space()->high_boundary());
 846   PSScavenge::reference_processor()->set_span(_reserved);
 847 
 848   MutableSpace* space_shrinking = NULL;
 849   if (from_space()->end() > to_space()->end()) {
 850     space_shrinking = from_space();
 851   } else {
 852     space_shrinking = to_space();
 853   }
 854 
 855   HeapWord* new_end = (HeapWord*)virtual_space()->high();
 856   assert(new_end >= space_shrinking->bottom(), "Shrink was too large");
 857   // Was there a shrink of the survivor space?
 858   if (new_end < space_shrinking->end()) {
 859     MemRegion mr(space_shrinking->bottom(), new_end);
 860     space_shrinking->initialize(mr,
 861                                 SpaceDecorator::DontClear,
 862                                 SpaceDecorator::Mangle);
 863   }
 864 }
 865 
 866 // This method currently does not expect to expand into eden (i.e.,
 867 // the virtual space boundaries is expected to be consistent
 868 // with the eden boundaries..
 869 void PSYoungGen::post_resize() {
 870   assert_locked_or_safepoint(Heap_lock);
 871   assert((eden_space()->bottom() < to_space()->bottom()) &&
 872          (eden_space()->bottom() < from_space()->bottom()),
 873          "Eden is assumed to be below the survivor spaces");
 874 
 875   MemRegion cmr((HeapWord*)virtual_space()->low(),
 876                 (HeapWord*)virtual_space()->high());
 877   ParallelScavengeHeap::heap()->barrier_set()->resize_covered_region(cmr);
 878   space_invariants();
 879 }
 880 
 881 
 882 
 883 void PSYoungGen::update_counters() {
 884   if (UsePerfData) {
 885     _eden_counters->update_all();
 886     _from_counters->update_all();
 887     _to_counters->update_all();
 888     _gen_counters->update_all();
 889   }
 890 }
 891 
 892 void PSYoungGen::verify() {
 893   eden_space()->verify();
 894   from_space()->verify();
 895   to_space()->verify();
 896 }
 897 
 898 #ifndef PRODUCT
 899 void PSYoungGen::record_spaces_top() {
 900   assert(ZapUnusedHeapArea, "Not mangling unused space");
 901   eden_space()->set_top_for_allocations();
 902   from_space()->set_top_for_allocations();
 903   to_space()->set_top_for_allocations();
 904 }
 905 #endif