src/share/vm/gc_implementation/g1/g1PageBasedVirtualSpace.hpp

rev 7618 : 8062063: Usage of UseHugeTLBFS, UseLargePagesInMetaspace and huge SurvivorAlignmentInBytes cause crashes in CMBitMapClosure::do_bit
Summary: Making sure committed memory is cleared when re-committed, even if using large pages.
Reviewed-by:
rev 7619 : [mq]: clear-in-listener
rev 7620 : [mq]: needs-zeroing-to-dirty

@@ -47,10 +47,16 @@
   size_t _page_size;
 
   // Bitmap used for verification of commit/uncommit operations.
   BitMap _committed;
 
+  // Bitmap used to keep track of which pages are dirty or not for _special
+  // spaces. This is needed because for those spaces the underlying memory
+  // will only be zero filled the first time it is committed. Calls to commit
+  // will use this bitmap and return whether or not the memory is zero filled.
+  BitMap _dirty;
+
   // Indicates that the entire space has been committed and pinned in memory,
   // os::commit_memory() or os::uncommit_memory() have no function.
   bool _special;
 
   // Indicates whether the committed space should be executable.

@@ -69,16 +75,15 @@
   bool is_area_uncommitted(uintptr_t start, size_t size_in_pages) const;
 
  public:
 
   // Commit the given area of pages starting at start being size_in_pages large.
-  MemRegion commit(uintptr_t start, size_t size_in_pages);
+  // Returns true if the given area is zero filled upon completion.
+  bool commit(uintptr_t start, size_t size_in_pages);
 
   // Uncommit the given area of pages starting at start being size_in_pages large.
-  MemRegion uncommit(uintptr_t start, size_t size_in_pages);
-
-  bool special() const { return _special; }
+  void uncommit(uintptr_t start, size_t size_in_pages);
 
   // Initialization
   G1PageBasedVirtualSpace();
   bool initialize_with_granularity(ReservedSpace rs, size_t page_size);