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hotspot/src/share/vm/gc_implementation/parallelScavenge/objectStartArray.cpp

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+/*
+ * Copyright 2001-2005 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/_objectStartArray.cpp.incl"
+
+void ObjectStartArray::initialize(MemRegion reserved_region) {
+  // We're based on the assumption that we use the same
+  // size blocks as the card table.
+  assert((int)block_size == (int)CardTableModRefBS::card_size, "Sanity");
+  assert((int)block_size <= 512, "block_size must be less than or equal to 512");
+
+  // Calculate how much space must be reserved
+  _reserved_region = reserved_region;
+
+  size_t bytes_to_reserve = reserved_region.word_size() / block_size_in_words;
+  assert(bytes_to_reserve > 0, "Sanity");
+
+  bytes_to_reserve =
+    align_size_up(bytes_to_reserve, os::vm_allocation_granularity());
+
+  // Do not use large-pages for the backing store. The one large page region
+  // will be used for the heap proper.
+  ReservedSpace backing_store(bytes_to_reserve);
+  if (!backing_store.is_reserved()) {
+    vm_exit_during_initialization("Could not reserve space for ObjectStartArray");
+  }
+
+  // We do not commit any memory initially
+  if (!_virtual_space.initialize(backing_store, 0)) {
+    vm_exit_during_initialization("Could not commit space for ObjectStartArray");
+  }
+
+  _raw_base = (jbyte*)_virtual_space.low_boundary();
+  if (_raw_base == NULL) {
+    vm_exit_during_initialization("Could not get raw_base address");
+  }
+
+  _offset_base = _raw_base - (size_t(reserved_region.start()) >> block_shift);
+
+  _covered_region.set_start(reserved_region.start());
+  _covered_region.set_word_size(0);
+
+  _blocks_region.set_start((HeapWord*)_raw_base);
+  _blocks_region.set_word_size(0);
+}
+
+void ObjectStartArray::set_covered_region(MemRegion mr) {
+  assert(_reserved_region.contains(mr), "MemRegion outside of reserved space");
+  assert(_reserved_region.start() == mr.start(), "Attempt to move covered region");
+
+  HeapWord* low_bound  = mr.start();
+  HeapWord* high_bound = mr.end();
+  assert((uintptr_t(low_bound)  & (block_size - 1))  == 0, "heap must start at block boundary");
+  assert((uintptr_t(high_bound) & (block_size - 1))  == 0, "heap must end at block boundary");
+
+  size_t requested_blocks_size_in_bytes = mr.word_size() / block_size_in_words;
+
+  // Only commit memory in page sized chunks
+  requested_blocks_size_in_bytes =
+    align_size_up(requested_blocks_size_in_bytes, os::vm_page_size());
+
+  _covered_region = mr;
+
+  size_t current_blocks_size_in_bytes = _blocks_region.byte_size();
+
+  if (requested_blocks_size_in_bytes > current_blocks_size_in_bytes) {
+    // Expand
+    size_t expand_by = requested_blocks_size_in_bytes - current_blocks_size_in_bytes;
+    if (!_virtual_space.expand_by(expand_by)) {
+      vm_exit_out_of_memory(expand_by, "object start array expansion");
+    }
+    // Clear *only* the newly allocated region
+    memset(_blocks_region.end(), clean_block, expand_by);
+  }
+
+  if (requested_blocks_size_in_bytes < current_blocks_size_in_bytes) {
+    // Shrink
+    size_t shrink_by = current_blocks_size_in_bytes - requested_blocks_size_in_bytes;
+    _virtual_space.shrink_by(shrink_by);
+  }
+
+  _blocks_region.set_word_size(requested_blocks_size_in_bytes / sizeof(HeapWord));
+
+  assert(requested_blocks_size_in_bytes % sizeof(HeapWord) == 0, "Block table not expanded in word sized increment");
+  assert(requested_blocks_size_in_bytes == _blocks_region.byte_size(), "Sanity");
+  assert(block_for_addr(low_bound) == &_raw_base[0], "Checking start of map");
+  assert(block_for_addr(high_bound-1) <= &_raw_base[_blocks_region.byte_size()-1], "Checking end of map");
+}
+
+void ObjectStartArray::reset() {
+  memset(_blocks_region.start(), clean_block, _blocks_region.byte_size());
+}
+
+
+bool ObjectStartArray::object_starts_in_range(HeapWord* start_addr,
+                                              HeapWord* end_addr) const {
+  assert(start_addr <= end_addr, "range is wrong");
+  if (start_addr > end_addr) {
+    return false;
+  }
+
+  jbyte* start_block = block_for_addr(start_addr);
+  jbyte* end_block = block_for_addr(end_addr);
+
+  for (jbyte* block = start_block; block <= end_block; block++) {
+    if (*block != clean_block) {
+      return true;
+    }
+  }
+  // No object starts in this slice; verify this using
+  // more traditional methods:
+  assert(object_start(end_addr - 1) <= start_addr,
+         "Oops an object does start in this slice?");
+  return false;
+}