8278756: Parallel: Drop PSOldGen::_reserved

Reviewed-by: tschatzl, mli

Author: albertnetymk

src/hotspot/share/gc/parallel/objectStartArray.hpp

@@ -41,6 +41,7 @@ class ObjectStartArray : public CHeapObj<mtGC> {
  private:
   PSVirtualSpace  _virtual_space;
   MemRegion       _reserved_region;
+  // The committed (old-gen heap) virtual space this object-start-array covers.
   MemRegion       _covered_region;
   MemRegion       _blocks_region;
   jbyte*          _raw_base;

src/hotspot/share/gc/parallel/parallelScavengeHeap.cpp

@@ -645,8 +645,10 @@ void ParallelScavengeHeap::prepare_for_verify() {
 PSHeapSummary ParallelScavengeHeap::create_ps_heap_summary() {
   PSOldGen* old = old_gen();
   HeapWord* old_committed_end = (HeapWord*)old->virtual_space()->committed_high_addr();
-  VirtualSpaceSummary old_summary(old->reserved().start(), old_committed_end, old->reserved().end());
-  SpaceSummary old_space(old->reserved().start(), old_committed_end, old->used_in_bytes());
+  HeapWord* old_reserved_start = old->reserved().start();
+  HeapWord* old_reserved_end = old->reserved().end();
+  VirtualSpaceSummary old_summary(old_reserved_start, old_committed_end, old_reserved_end);
+  SpaceSummary old_space(old_reserved_start, old_committed_end, old->used_in_bytes());
 
   PSYoungGen* young = young_gen();
   VirtualSpaceSummary young_summary(young->reserved().start(),

src/hotspot/share/gc/parallel/psOldGen.cpp

@@ -50,10 +50,6 @@ void PSOldGen::initialize(ReservedSpace rs, size_t initial_size, size_t alignmen
   initialize_virtual_space(rs, initial_size, alignment);
   initialize_work(perf_data_name, level);
 
-  // The old gen can grow to max_gen_size().  _reserve reflects only
-  // the current maximum that can be committed.
-  assert(_reserved.byte_size() <= max_gen_size(), "Consistency check");
-
   initialize_performance_counters(perf_data_name, level);
 }
 
@@ -69,66 +65,51 @@ void PSOldGen::initialize_virtual_space(ReservedSpace rs,
 }
 
 void PSOldGen::initialize_work(const char* perf_data_name, int level) {
-  //
-  // Basic memory initialization
-  //
-
-  MemRegion limit_reserved((HeapWord*)virtual_space()->low_boundary(),
-                           heap_word_size(max_gen_size()));
-  assert(limit_reserved.byte_size() == max_gen_size(),
-    "word vs bytes confusion");
-  //
-  // Object start stuff
-  //
+  MemRegion const reserved_mr = reserved();
+  assert(reserved_mr.byte_size() == max_gen_size(), "invariant");
 
-  start_array()->initialize(limit_reserved);
+  // Object start stuff: for all reserved memory
+  start_array()->initialize(reserved_mr);
 
-  _reserved = MemRegion((HeapWord*)virtual_space()->low_boundary(),
-                        (HeapWord*)virtual_space()->high_boundary());
+  // Card table stuff: for all committed memory
+  MemRegion committed_mr((HeapWord*)virtual_space()->low(),
+                         (HeapWord*)virtual_space()->high());
 
-  //
-  // Card table stuff
-  //
-
-  MemRegion cmr((HeapWord*)virtual_space()->low(),
-                (HeapWord*)virtual_space()->high());
   if (ZapUnusedHeapArea) {
     // Mangle newly committed space immediately rather than
     // waiting for the initialization of the space even though
     // mangling is related to spaces.  Doing it here eliminates
     // the need to carry along information that a complete mangling
     // (bottom to end) needs to be done.
-    SpaceMangler::mangle_region(cmr);
+    SpaceMangler::mangle_region(committed_mr);
   }
 
   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
   PSCardTable* ct = heap->card_table();
-  ct->resize_covered_region(cmr);
+  ct->resize_covered_region(committed_mr);
 
   // Verify that the start and end of this generation is the start of a card.
   // If this wasn't true, a single card could span more than one generation,
   // which would cause problems when we commit/uncommit memory, and when we
   // clear and dirty cards.
-  guarantee(ct->is_card_aligned(_reserved.start()), "generation must be card aligned");
-  if (_reserved.end() != heap->reserved_region().end()) {
-    // Don't check at the very end of the heap as we'll assert that we're probing off
-    // the end if we try.
-    guarantee(ct->is_card_aligned(_reserved.end()), "generation must be card aligned");
-  }
+  guarantee(ct->is_card_aligned(reserved_mr.start()), "generation must be card aligned");
+  // Check the heap layout documented at `class ParallelScavengeHeap`.
+  assert(reserved_mr.end() != heap->reserved_region().end(), "invariant");
+  guarantee(ct->is_card_aligned(reserved_mr.end()), "generation must be card aligned");
 
   //
   // ObjectSpace stuff
   //
 
   _object_space = new MutableSpace(virtual_space()->alignment());
-  object_space()->initialize(cmr,
+  object_space()->initialize(committed_mr,
                              SpaceDecorator::Clear,
                              SpaceDecorator::Mangle,
                              MutableSpace::SetupPages,
                              &ParallelScavengeHeap::heap()->workers());
 
   // Update the start_array
-  start_array()->set_covered_region(cmr);
+  start_array()->set_covered_region(committed_mr);
 }
 
 void PSOldGen::initialize_performance_counters(const char* perf_data_name, int level) {
@@ -314,7 +295,6 @@ void PSOldGen::resize(size_t desired_free_space) {
   // Adjust according to our min and max
   new_size = clamp(new_size, min_gen_size(), max_gen_size());
 
-  assert(max_gen_size() >= reserved().byte_size(), "max new size problem?");
   new_size = align_up(new_size, alignment);
 
   const size_t current_size = capacity_in_bytes();

src/hotspot/share/gc/parallel/psOldGen.hpp

@@ -34,9 +34,7 @@
 
 class PSOldGen : public CHeapObj<mtGC> {
   friend class VMStructs;
-
  private:
-  MemRegion                _reserved;          // Used for simple containment tests
   PSVirtualSpace*          _virtual_space;     // Controls mapping and unmapping of virtual mem
   ObjectStartArray         _start_array;       // Keeps track of where objects start in a 512b block
   MutableSpace*            _object_space;      // Where all the objects live
@@ -99,16 +97,20 @@ class PSOldGen : public CHeapObj<mtGC> {
   PSOldGen(ReservedSpace rs, size_t initial_size, size_t min_size,
            size_t max_size, const char* perf_data_name, int level);
 
-  MemRegion reserved() const { return _reserved; }
+  MemRegion reserved() const {
+    return MemRegion((HeapWord*)(_virtual_space->low_boundary()),
+                     (HeapWord*)(_virtual_space->high_boundary()));
+  }
+
   size_t max_gen_size() const { return _max_gen_size; }
   size_t min_gen_size() const { return _min_gen_size; }
 
   bool is_in(const void* p) const           {
-    return _virtual_space->contains((void *)p);
+    return _virtual_space->is_in_committed((void *)p);
   }
 
   bool is_in_reserved(const void* p) const {
-    return reserved().contains(p);
+    return _virtual_space->is_in_reserved(p);
   }
 
   MutableSpace*         object_space() const      { return _object_space; }

src/hotspot/share/gc/parallel/psParallelCompact.cpp

@@ -1041,9 +1041,9 @@ void PSParallelCompact::post_compact()
   PSCardTable* ct = heap->card_table();
   MemRegion old_mr = heap->old_gen()->reserved();
   if (young_gen_empty) {
-    ct->clear(MemRegion(old_mr.start(), old_mr.end()));
+    ct->clear(old_mr);
   } else {
-    ct->invalidate(MemRegion(old_mr.start(), old_mr.end()));
+    ct->invalidate(old_mr);
   }
 
   // Delete metaspaces for unloaded class loaders and clean up loader_data graph

src/hotspot/share/gc/parallel/psVirtualspace.cpp

@@ -66,11 +66,6 @@ PSVirtualSpace::~PSVirtualSpace() {
   release();
 }
 
-bool PSVirtualSpace::contains(void* p) const {
-  char* const cp = (char*)p;
-  return cp >= committed_low_addr() && cp < committed_high_addr();
-}
-
 void PSVirtualSpace::release() {
   DEBUG_ONLY(PSVirtualSpaceVerifier this_verifier(this));
   // This may not release memory it didn't reserve.

src/hotspot/share/gc/parallel/psVirtualspace.hpp

@@ -75,7 +75,13 @@ class PSVirtualSpace : public CHeapObj<mtGC> {
   PSVirtualSpace();
   void initialize(ReservedSpace rs);
 
-  bool contains(void* p)      const;
+  bool is_in_committed(const void* p) const {
+    return (p >= committed_low_addr()) && (p < committed_high_addr());
+  }
+
+  bool is_in_reserved(const void* p) const {
+    return (p >= reserved_low_addr()) && (p < reserved_high_addr());
+  }
 
   // Accessors (all sizes are bytes).
   size_t alignment()          const { return _alignment; }
@@ -85,6 +91,7 @@ class PSVirtualSpace : public CHeapObj<mtGC> {
   char* committed_high_addr() const { return _committed_high_addr; }
   bool  special()             const { return _special; }
 
+  // Return size in bytes
   inline size_t committed_size()   const;
   inline size_t reserved_size()    const;
   inline size_t uncommitted_size() const;

src/hotspot/share/gc/parallel/psYoungGen.hpp

@@ -90,7 +90,7 @@ class PSYoungGen : public CHeapObj<mtGC> {
   MemRegion reserved() const { return _reserved; }
 
   bool is_in(const void* p) const {
-    return _virtual_space->contains((void *)p);
+    return _virtual_space->is_in_committed(p);
   }
 
   bool is_in_reserved(const void* p) const {

src/hotspot/share/gc/parallel/vmStructs_parallelgc.hpp

@@ -57,7 +57,6 @@
   nonstatic_field(PSYoungGen,                  _min_gen_size,                                 const size_t)                          \
   nonstatic_field(PSYoungGen,                  _max_gen_size,                                 const size_t)                          \
                                                                                                                                      \
-  nonstatic_field(PSOldGen,                    _reserved,                                     MemRegion)                             \
   nonstatic_field(PSOldGen,                    _virtual_space,                                PSVirtualSpace*)                       \
   nonstatic_field(PSOldGen,                    _object_space,                                 MutableSpace*)                         \
   nonstatic_field(PSOldGen,                    _min_gen_size,                                 const size_t)                          \