# HG changeset patch
# User tamao
# Date 1362526616 28800
# Node ID 9def4075da6d03d0cab0d03f1519a6b7b7e43054
# Parent  d778bb46a9a508113cbb1dfd59a48ef5a27ff91a
8008079: G1: Add nextObject routine to CMBitMapRO and replace nextWord
Summary: Update the task local finger to the start of the next object when marking aborts, in order to avoid the redundant scanning of all 0's when the marking task restarts, if otherwise updating to the next word. In addition, reuse the routine nextObject() in routine iterate().
Reviewed-by: johnc, ysr
Contributed-by: tamao <tao.mao@oracle.com>

diff -r d778bb46a9a5 -r 9def4075da6d src/share/vm/gc_implementation/g1/concurrentMark.cpp
--- a/src/share/vm/gc_implementation/g1/concurrentMark.cpp	Mon Mar 04 22:39:00 2013 -0800
+++ b/src/share/vm/gc_implementation/g1/concurrentMark.cpp	Tue Mar 05 15:36:56 2013 -0800
@@ -4111,7 +4111,7 @@
         // bitmap knows by how much we need to move it as it knows its
         // granularity).
         assert(_finger < _region_limit, "invariant");
-        HeapWord* new_finger = _nextMarkBitMap->nextWord(_finger);
+        HeapWord* new_finger = _nextMarkBitMap->nextObject(_finger);
         // Check if bitmap iteration was aborted while scanning the last object
         if (new_finger >= _region_limit) {
           giveup_current_region();
diff -r d778bb46a9a5 -r 9def4075da6d src/share/vm/gc_implementation/g1/concurrentMark.hpp
--- a/src/share/vm/gc_implementation/g1/concurrentMark.hpp	Mon Mar 04 22:39:00 2013 -0800
+++ b/src/share/vm/gc_implementation/g1/concurrentMark.hpp	Tue Mar 05 15:36:56 2013 -0800
@@ -97,7 +97,6 @@
                                        HeapWord* limit = NULL) const;
 
   // conversion utilities
-  // XXX Fix these so that offsets are size_t's...
   HeapWord* offsetToHeapWord(size_t offset) const {
     return _bmStartWord + (offset << _shifter);
   }
@@ -105,8 +104,13 @@
     return pointer_delta(addr, _bmStartWord) >> _shifter;
   }
   int heapWordDiffToOffsetDiff(size_t diff) const;
-  HeapWord* nextWord(HeapWord* addr) {
-    return offsetToHeapWord(heapWordToOffset(addr) + 1);
+
+  // The argument addr should be the start address of a valid object
+  HeapWord* nextObject(HeapWord* addr) {
+    oop obj = (oop) addr;
+    HeapWord* res =  addr + obj->size();
+    assert(offsetToHeapWord(heapWordToOffset(res)) == res, "sanity");
+    return res;
   }
 
   // debugging
diff -r d778bb46a9a5 -r 9def4075da6d src/share/vm/gc_implementation/g1/concurrentMark.inline.hpp
--- a/src/share/vm/gc_implementation/g1/concurrentMark.inline.hpp	Mon Mar 04 22:39:00 2013 -0800
+++ b/src/share/vm/gc_implementation/g1/concurrentMark.inline.hpp	Tue Mar 05 15:36:56 2013 -0800
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2013, 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
@@ -252,12 +252,10 @@
 
     start_offset = _bm.get_next_one_offset(start_offset, end_offset);
     while (start_offset < end_offset) {
-      HeapWord* obj_addr = offsetToHeapWord(start_offset);
-      oop obj = (oop) obj_addr;
       if (!cl->do_bit(start_offset)) {
         return false;
       }
-      HeapWord* next_addr = MIN2(obj_addr + obj->size(), end_addr);
+      HeapWord* next_addr = MIN2(nextObject(offsetToHeapWord(start_offset)), end_addr);
       BitMap::idx_t next_offset = heapWordToOffset(next_addr);
       start_offset = _bm.get_next_one_offset(next_offset, end_offset);
     }