--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/vm/gc_implementation/parNew/asParNewGeneration.cpp	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,630 @@
+/*
+ * Copyright 2005-2006 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+# include "incls/_precompiled.incl"
+# include "incls/_asParNewGeneration.cpp.incl"
+
+ASParNewGeneration::ASParNewGeneration(ReservedSpace rs,
+                                       size_t initial_byte_size,
+                                       size_t min_byte_size,
+                                       int level) :
+  ParNewGeneration(rs, initial_byte_size, level),
+  _min_gen_size(min_byte_size) {}
+
+const char* ASParNewGeneration::name() const {
+  return "adaptive size par new generation";
+}
+
+void ASParNewGeneration::adjust_desired_tenuring_threshold() {
+  assert(UseAdaptiveSizePolicy,
+    "Should only be used with UseAdaptiveSizePolicy");
+}
+
+void ASParNewGeneration::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(), capacity(),
+        max_gen_size(), min_gen_size());
+    }
+  }
+}
+
+size_t ASParNewGeneration::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 ASParNewGeneration::available_to_live() const {
+#undef SHRINKS_AT_END_OF_EDEN
+#ifdef SHRINKS_AT_END_OF_EDEN
+  size_t delta_in_survivor = 0;
+  ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
+  const size_t space_alignment = heap->intra_generation_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;
+#else
+  // The only space available for shrinking is in to-space if it
+  // is above from-space.
+  if (to()->bottom() > from()->bottom()) {
+    const size_t alignment = os::vm_page_size();
+    if (to()->capacity() < alignment) {
+      return 0;
+    } else {
+      return to()->capacity() - alignment;
+    }
+  } else {
+    return 0;
+  }
+#endif
+}
+
+// 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 ASParNewGeneration::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, os::vm_page_size());
+}
+
+// Note that the the alignment used is the OS page size as
+// opposed to an alignment associated with the virtual space
+// (as is done in the ASPSYoungGen/ASPSOldGen)
+bool ASParNewGeneration::resize_generation(size_t eden_size,
+                                           size_t survivor_size) {
+  const size_t alignment = os::vm_page_size();
+  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_gen_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_gen_size()),
+                             min_gen_size());
+  assert(desired_size <= max_gen_size(), "just checking");
+
+  if (desired_size > orig_size) {
+    // Grow the generation
+    size_t change = desired_size - orig_size;
+    assert(change % alignment == 0, "just checking");
+    if (!virtual_space()->expand_by(change)) {
+      return false; // Error if we fail to resize!
+    }
+
+    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 == max_gen_size()) {
+        gclog_or_tty->print_cr("ASParNew generation size at maximum: "
+          SIZE_FORMAT "K", orig_size/K);
+      } else if (orig_size == min_gen_size()) {
+        gclog_or_tty->print_cr("ASParNew generation size at minium: "
+          SIZE_FORMAT "K", orig_size/K);
+      }
+    }
+  }
+
+  if (size_changed) {
+    MemRegion cmr((HeapWord*)virtual_space()->low(),
+                  (HeapWord*)virtual_space()->high());
+    GenCollectedHeap::heap()->barrier_set()->resize_covered_region(cmr);
+
+    if (Verbose && PrintGC) {
+      size_t current_size  = virtual_space()->committed_size();
+      gclog_or_tty->print_cr("ASParNew 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_gen_size(), "Sanity");
+
+  return true;
+}
+
+void ASParNewGeneration::reset_survivors_after_shrink() {
+
+  GenCollectedHeap* gch = GenCollectedHeap::heap();
+  HeapWord* new_end = (HeapWord*)virtual_space()->high();
+
+  if (from()->end() > to()->end()) {
+    assert(new_end >= from()->end(), "Shrinking past from-space");
+  } else {
+    assert(new_end >= to()->bottom(), "Shrink was too large");
+    // Was there a shrink of the survivor space?
+    if (new_end < to()->end()) {
+      MemRegion mr(to()->bottom(), new_end);
+      to()->initialize(mr, false /* clear */);
+    }
+  }
+}
+void ASParNewGeneration::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");
+  CollectedHeap* heap = Universe::heap();
+  assert(heap->kind() == CollectedHeap::GenCollectedHeap, "Sanity");
+
+
+  // We require eden and to space to be empty
+  if ((!eden()->is_empty()) || (!to()->is_empty())) {
+    return;
+  }
+
+  size_t cur_eden_size = eden()->capacity();
+
+  if (PrintAdaptiveSizePolicy && Verbose) {
+    gclog_or_tty->print_cr("ASParNew::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()->bottom(),
+                  eden()->end(),
+                  pointer_delta(eden()->end(),
+                                eden()->bottom(),
+                                sizeof(char)));
+    gclog_or_tty->print_cr("    from: [" PTR_FORMAT ".." PTR_FORMAT ") "
+                  SIZE_FORMAT,
+                  from()->bottom(),
+                  from()->end(),
+                  pointer_delta(from()->end(),
+                                from()->bottom(),
+                                sizeof(char)));
+    gclog_or_tty->print_cr("      to: [" PTR_FORMAT ".." PTR_FORMAT ") "
+                  SIZE_FORMAT,
+                  to()->bottom(),
+                  to()->end(),
+                  pointer_delta(  to()->end(),
+                                  to()->bottom(),
+                                  sizeof(char)));
+  }
+
+  // There's nothing to do if the new sizes are the same as the current
+  if (requested_survivor_size == to()->capacity() &&
+      requested_survivor_size == from()->capacity() &&
+      requested_eden_size == eden()->capacity()) {
+    if (PrintAdaptiveSizePolicy && Verbose) {
+      gclog_or_tty->print_cr("    capacities are the right sizes, returning");
+    }
+    return;
+  }
+
+  char* eden_start = (char*)eden()->bottom();
+  char* eden_end   = (char*)eden()->end();
+  char* from_start = (char*)from()->bottom();
+  char* from_end   = (char*)from()->end();
+  char* to_start   = (char*)to()->bottom();
+  char* to_end     = (char*)to()->end();
+
+  const size_t alignment = os::vm_page_size();
+  const bool maintain_minimum =
+    (requested_eden_size + 2 * requested_survivor_size) <= min_gen_size();
+
+  // Check whether from space is below to space
+  if (from_start < to_start) {
+    // Eden, from, to
+    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)));
+    }
+
+// tty->print_cr("eden_size before: " SIZE_FORMAT, eden_size);
+    eden_size = align_size_down(eden_size, alignment);
+// tty->print_cr("eden_size after: " SIZE_FORMAT, eden_size);
+    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()->end()) {
+      // Calculate the minimum offset possible for from_end
+      size_t from_size = pointer_delta(from()->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()->end(), "from_end moved to the right");
+
+      // Now update to_start with the new from_end
+      to_start = MAX2(from_end, to_start);
+    } else {
+      // If shrinking, move to-space down to abut the end of from-space
+      // so that shrinking will move to-space down.  If not shrinking
+      // to-space is moving up to allow for growth on the next expansion.
+      if (requested_eden_size <= cur_eden_size) {
+        to_start = from_end;
+        if (to_start + requested_survivor_size > to_start) {
+          to_end = to_start + requested_survivor_size;
+        }
+      }
+      // else leave to_end pointing to the high end of the virtual space.
+    }
+
+    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:");
+    }
+
+    // Calculate the to-space boundaries based on
+    // the start of from-space.
+    to_end = from_start;
+    to_start = (char*)pointer_delta(from_start,
+                                    (char*)requested_survivor_size,
+                                    sizeof(char));
+    // Calculate the ideal eden boundaries.
+    // eden_end is already at the bottom of the generation
+    assert(eden_start == virtual_space()->low(),
+      "Eden is not starting at the low end of the virtual space");
+    if (eden_start + requested_eden_size >= eden_start) {
+      eden_end = eden_start + requested_eden_size;
+    } else {
+      eden_end = to_start;
+    }
+
+    // Does eden intrude into to-space?  to-space
+    // gets priority but eden is not allowed to shrink
+    // to 0.
+    if (eden_end > to_start) {
+      eden_end = to_start;
+    }
+
+    // Don't let eden shrink down to 0 or less.
+    eden_end = MAX2(eden_end, eden_start + alignment);
+    assert(eden_start + alignment >= eden_start, "Overflow");
+
+    size_t eden_size;
+    if (maintain_minimum) {
+      // Use all the space available.
+      eden_end = MAX2(eden_end, to_start);
+      eden_size = pointer_delta(eden_end, eden_start, sizeof(char));
+      eden_size = MIN2(eden_size, cur_eden_size);
+    } else {
+      eden_size = pointer_delta(eden_end, eden_start, sizeof(char));
+    }
+    eden_size = align_size_down(eden_size, alignment);
+    assert(maintain_minimum || eden_size <= requested_eden_size,
+      "Eden size is too large");
+    assert(eden_size >= alignment, "Eden size is too small");
+    eden_end = eden_start + eden_size;
+
+    // Move to-space down to eden.
+    if (requested_eden_size < cur_eden_size) {
+      to_start = eden_end;
+      if (to_start + requested_survivor_size > to_start) {
+        to_end = MIN2(from_start, to_start + requested_survivor_size);
+      } else {
+        to_end = from_start;
+      }
+    }
+
+    // eden_end may have moved so again make sure
+    // the to-space and eden don't overlap.
+    to_start = MAX2(eden_end, to_start);
+
+    // from-space
+    size_t from_used = from()->used();
+    if (requested_survivor_size > from_used) {
+      if (from_start + requested_survivor_size >= from_start) {
+        from_end = from_start + requested_survivor_size;
+      }
+      if (from_end > virtual_space()->high()) {
+        from_end = virtual_space()->high();
+      }
+    }
+
+    assert(to_start >= eden_end, "to-space should be above eden");
+    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()->bottom(),
+            "from start moved to the right");
+  guarantee((HeapWord*)from_end >= from()->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()->top();
+
+  // For PrintAdaptiveSizePolicy block  below
+  size_t old_from = from()->capacity();
+  size_t old_to   = to()->capacity();
+
+  // The call to initialize NULL's the next compaction space
+  eden()->initialize(edenMR, true);
+  eden()->set_next_compaction_space(from());
+    to()->initialize(toMR  , true);
+  from()->initialize(fromMR, false);     // Note, not cleared!
+
+  assert(from()->top() == old_from_top, "from top changed!");
+
+  if (PrintAdaptiveSizePolicy) {
+    GenCollectedHeap* gch = GenCollectedHeap::heap();
+    assert(gch->kind() == CollectedHeap::GenCollectedHeap, "Sanity");
+
+    gclog_or_tty->print("AdaptiveSizePolicy::survivor space sizes: "
+                  "collection: %d "
+                  "(" SIZE_FORMAT ", " SIZE_FORMAT ") -> "
+                  "(" SIZE_FORMAT ", " SIZE_FORMAT ") ",
+                  gch->total_collections(),
+                  old_from, old_to,
+                  from()->capacity(),
+                  to()->capacity());
+    gclog_or_tty->cr();
+  }
+}
+
+void ASParNewGeneration::compute_new_size() {
+  GenCollectedHeap* gch = GenCollectedHeap::heap();
+  assert(gch->kind() == CollectedHeap::GenCollectedHeap,
+    "not a CMS generational heap");
+
+
+  CMSAdaptiveSizePolicy* size_policy =
+    (CMSAdaptiveSizePolicy*)gch->gen_policy()->size_policy();
+  assert(size_policy->is_gc_cms_adaptive_size_policy(),
+    "Wrong type of size policy");
+
+  size_t survived = from()->used();
+  if (!survivor_overflow()) {
+    // Keep running averages on how much survived
+    size_policy->avg_survived()->sample(survived);
+  } else {
+    size_t promoted =
+      (size_t) next_gen()->gc_stats()->avg_promoted()->last_sample();
+    assert(promoted < gch->capacity(), "Conversion problem?");
+    size_t survived_guess = survived + promoted;
+    size_policy->avg_survived()->sample(survived_guess);
+  }
+
+  size_t survivor_limit = max_survivor_size();
+  _tenuring_threshold =
+    size_policy->compute_survivor_space_size_and_threshold(
+                                                     _survivor_overflow,
+                                                     _tenuring_threshold,
+                                                     survivor_limit);
+  size_policy->avg_young_live()->sample(used());
+  size_policy->avg_eden_live()->sample(eden()->used());
+
+  size_policy->compute_young_generation_free_space(eden()->capacity(),
+                                                   max_gen_size());
+
+  resize(size_policy->calculated_eden_size_in_bytes(),
+         size_policy->calculated_survivor_size_in_bytes());
+
+  if (UsePerfData) {
+    CMSGCAdaptivePolicyCounters* counters =
+      (CMSGCAdaptivePolicyCounters*) gch->collector_policy()->counters();
+    assert(counters->kind() ==
+           GCPolicyCounters::CMSGCAdaptivePolicyCountersKind,
+      "Wrong kind of counters");
+    counters->update_tenuring_threshold(_tenuring_threshold);
+    counters->update_survivor_overflowed(_survivor_overflow);
+    counters->update_young_capacity(capacity());
+  }
+}
+
+
+#ifndef PRODUCT
+// Changes from PSYoungGen version
+//      value of "alignment"
+void ASParNewGeneration::space_invariants() {
+  const size_t alignment = os::vm_page_size();
+
+  // Currently, our eden size cannot shrink to zero
+  guarantee(eden()->capacity() >= alignment, "eden too small");
+  guarantee(from()->capacity() >= alignment, "from too small");
+  guarantee(to()->capacity() >= alignment, "to too small");
+
+  // Relationship of spaces to each other
+  char* eden_start = (char*)eden()->bottom();
+  char* eden_end   = (char*)eden()->end();
+  char* from_start = (char*)from()->bottom();
+  char* from_end   = (char*)from()->end();
+  char* to_start   = (char*)to()->bottom();
+  char* to_end     = (char*)to()->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()->capacity() +
+     to()->capacity() +
+     from()->capacity()), "Committed size is inconsistent");
+  assert(virtual_space()->committed_size() <= virtual_space()->reserved_size(),
+    "Space invariant");
+  char* eden_top = (char*)eden()->top();
+  char* from_top = (char*)from()->top();
+  char* to_top = (char*)to()->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");
+}
+#endif