--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/vm/gc_implementation/parNew/parCardTableModRefBS.cpp	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,315 @@
+/*
+ * Copyright (c) 2007 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/_parCardTableModRefBS.cpp.incl"
+
+void CardTableModRefBS::par_non_clean_card_iterate_work(Space* sp, MemRegion mr,
+                                                        DirtyCardToOopClosure* dcto_cl,
+                                                        MemRegionClosure* cl,
+                                                        bool clear,
+                                                        int n_threads) {
+  if (n_threads > 0) {
+    assert(n_threads == (int)ParallelGCThreads, "# worker threads != # requested!");
+
+      // Make sure the LNC array is valid for the space.
+    jbyte**   lowest_non_clean;
+    uintptr_t lowest_non_clean_base_chunk_index;
+    size_t    lowest_non_clean_chunk_size;
+    get_LNC_array_for_space(sp, lowest_non_clean,
+                            lowest_non_clean_base_chunk_index,
+                            lowest_non_clean_chunk_size);
+
+    int n_strides = n_threads * StridesPerThread;
+    SequentialSubTasksDone* pst = sp->par_seq_tasks();
+    pst->set_par_threads(n_threads);
+    pst->set_n_tasks(n_strides);
+
+    int stride = 0;
+    while (!pst->is_task_claimed(/* reference */ stride)) {
+      process_stride(sp, mr, stride, n_strides, dcto_cl, cl, clear,
+                     lowest_non_clean,
+                     lowest_non_clean_base_chunk_index,
+                     lowest_non_clean_chunk_size);
+    }
+    if (pst->all_tasks_completed()) {
+      // Clear lowest_non_clean array for next time.
+      intptr_t first_chunk_index = addr_to_chunk_index(mr.start());
+      uintptr_t last_chunk_index  = addr_to_chunk_index(mr.last());
+      for (uintptr_t ch = first_chunk_index; ch <= last_chunk_index; ch++) {
+        intptr_t ind = ch - lowest_non_clean_base_chunk_index;
+        assert(0 <= ind && ind < (intptr_t)lowest_non_clean_chunk_size,
+               "Bounds error");
+        lowest_non_clean[ind] = NULL;
+      }
+    }
+  }
+}
+
+void
+CardTableModRefBS::
+process_stride(Space* sp,
+               MemRegion used,
+               jint stride, int n_strides,
+               DirtyCardToOopClosure* dcto_cl,
+               MemRegionClosure* cl,
+               bool clear,
+               jbyte** lowest_non_clean,
+               uintptr_t lowest_non_clean_base_chunk_index,
+               size_t    lowest_non_clean_chunk_size) {
+  // We don't have to go downwards here; it wouldn't help anyway,
+  // because of parallelism.
+
+  // Find the first card address of the first chunk in the stride that is
+  // at least "bottom" of the used region.
+  jbyte*    start_card  = byte_for(used.start());
+  jbyte*    end_card    = byte_after(used.last());
+  uintptr_t start_chunk = addr_to_chunk_index(used.start());
+  uintptr_t start_chunk_stride_num = start_chunk % n_strides;
+  jbyte* chunk_card_start;
+
+  if ((uintptr_t)stride >= start_chunk_stride_num) {
+    chunk_card_start = (jbyte*)(start_card +
+                                (stride - start_chunk_stride_num) *
+                                CardsPerStrideChunk);
+  } else {
+    // Go ahead to the next chunk group boundary, then to the requested stride.
+    chunk_card_start = (jbyte*)(start_card +
+                                (n_strides - start_chunk_stride_num + stride) *
+                                CardsPerStrideChunk);
+  }
+
+  while (chunk_card_start < end_card) {
+    // We don't have to go downwards here; it wouldn't help anyway,
+    // because of parallelism.  (We take care with "min_done"; see below.)
+    // Invariant: chunk_mr should be fully contained within the "used" region.
+    jbyte*    chunk_card_end = chunk_card_start + CardsPerStrideChunk;
+    MemRegion chunk_mr       = MemRegion(addr_for(chunk_card_start),
+                                         chunk_card_end >= end_card ?
+                                           used.end() : addr_for(chunk_card_end));
+    assert(chunk_mr.word_size() > 0, "[chunk_card_start > used_end)");
+    assert(used.contains(chunk_mr), "chunk_mr should be subset of used");
+
+    // Process the chunk.
+    process_chunk_boundaries(sp,
+                             dcto_cl,
+                             chunk_mr,
+                             used,
+                             lowest_non_clean,
+                             lowest_non_clean_base_chunk_index,
+                             lowest_non_clean_chunk_size);
+
+    non_clean_card_iterate_work(chunk_mr, cl, clear);
+
+    // Find the next chunk of the stride.
+    chunk_card_start += CardsPerStrideChunk * n_strides;
+  }
+}
+
+void
+CardTableModRefBS::
+process_chunk_boundaries(Space* sp,
+                         DirtyCardToOopClosure* dcto_cl,
+                         MemRegion chunk_mr,
+                         MemRegion used,
+                         jbyte** lowest_non_clean,
+                         uintptr_t lowest_non_clean_base_chunk_index,
+                         size_t    lowest_non_clean_chunk_size)
+{
+  // We must worry about the chunk boundaries.
+
+  // First, set our max_to_do:
+  HeapWord* max_to_do = NULL;
+  uintptr_t cur_chunk_index = addr_to_chunk_index(chunk_mr.start());
+  cur_chunk_index           = cur_chunk_index - lowest_non_clean_base_chunk_index;
+
+  if (chunk_mr.end() < used.end()) {
+    // This is not the last chunk in the used region.  What is the last
+    // object?
+    HeapWord* last_block = sp->block_start(chunk_mr.end());
+    assert(last_block <= chunk_mr.end(), "In case this property changes.");
+    if (last_block == chunk_mr.end()
+        || !sp->block_is_obj(last_block)) {
+      max_to_do = chunk_mr.end();
+
+    } else {
+      // It is an object and starts before the end of the current chunk.
+      // last_obj_card is the card corresponding to the start of the last object
+      // in the chunk.  Note that the last object may not start in
+      // the chunk.
+      jbyte* last_obj_card = byte_for(last_block);
+      if (!card_may_have_been_dirty(*last_obj_card)) {
+        // The card containing the head is not dirty.  Any marks in
+        // subsequent cards still in this chunk must have been made
+        // precisely; we can cap processing at the end.
+        max_to_do = chunk_mr.end();
+      } else {
+        // The last object must be considered dirty, and extends onto the
+        // following chunk.  Look for a dirty card in that chunk that will
+        // bound our processing.
+        jbyte* limit_card = NULL;
+        size_t last_block_size = sp->block_size(last_block);
+        jbyte* last_card_of_last_obj =
+          byte_for(last_block + last_block_size - 1);
+        jbyte* first_card_of_next_chunk = byte_for(chunk_mr.end());
+        // This search potentially goes a long distance looking
+        // for the next card that will be scanned.  For example,
+        // an object that is an array of primitives will not
+        // have any cards covering regions interior to the array
+        // that will need to be scanned. The scan can be terminated
+        // at the last card of the next chunk.  That would leave
+        // limit_card as NULL and would result in "max_to_do"
+        // being set with the LNC value or with the end
+        // of the last block.
+        jbyte* last_card_of_next_chunk = first_card_of_next_chunk +
+          CardsPerStrideChunk;
+        assert(byte_for(chunk_mr.end()) - byte_for(chunk_mr.start())
+          == CardsPerStrideChunk, "last card of next chunk may be wrong");
+        jbyte* last_card_to_check = (jbyte*) MIN2(last_card_of_last_obj,
+                                                  last_card_of_next_chunk);
+        for (jbyte* cur = first_card_of_next_chunk;
+             cur <= last_card_to_check; cur++) {
+          if (card_will_be_scanned(*cur)) {
+            limit_card = cur; break;
+          }
+        }
+        assert(0 <= cur_chunk_index+1 &&
+               cur_chunk_index+1 < lowest_non_clean_chunk_size,
+               "Bounds error.");
+        // LNC for the next chunk
+        jbyte* lnc_card = lowest_non_clean[cur_chunk_index+1];
+        if (limit_card == NULL) {
+          limit_card = lnc_card;
+        }
+        if (limit_card != NULL) {
+          if (lnc_card != NULL) {
+            limit_card = (jbyte*)MIN2((intptr_t)limit_card,
+                                      (intptr_t)lnc_card);
+          }
+          max_to_do = addr_for(limit_card);
+        } else {
+          max_to_do = last_block + last_block_size;
+        }
+      }
+    }
+    assert(max_to_do != NULL, "OOPS!");
+  } else {
+    max_to_do = used.end();
+  }
+  // Now we can set the closure we're using so it doesn't to beyond
+  // max_to_do.
+  dcto_cl->set_min_done(max_to_do);
+#ifndef PRODUCT
+  dcto_cl->set_last_bottom(max_to_do);
+#endif
+
+  // Now we set *our" lowest_non_clean entry.
+  // Find the object that spans our boundary, if one exists.
+  // Nothing to do on the first chunk.
+  if (chunk_mr.start() > used.start()) {
+    // first_block is the block possibly spanning the chunk start
+    HeapWord* first_block = sp->block_start(chunk_mr.start());
+    // Does the block span the start of the chunk and is it
+    // an object?
+    if (first_block < chunk_mr.start() &&
+        sp->block_is_obj(first_block)) {
+      jbyte* first_dirty_card = NULL;
+      jbyte* last_card_of_first_obj =
+          byte_for(first_block + sp->block_size(first_block) - 1);
+      jbyte* first_card_of_cur_chunk = byte_for(chunk_mr.start());
+      jbyte* last_card_of_cur_chunk = byte_for(chunk_mr.last());
+      jbyte* last_card_to_check =
+        (jbyte*) MIN2((intptr_t) last_card_of_cur_chunk,
+                      (intptr_t) last_card_of_first_obj);
+      for (jbyte* cur = first_card_of_cur_chunk;
+           cur <= last_card_to_check; cur++) {
+        if (card_will_be_scanned(*cur)) {
+          first_dirty_card = cur; break;
+        }
+      }
+      if (first_dirty_card != NULL) {
+        assert(0 <= cur_chunk_index &&
+                 cur_chunk_index < lowest_non_clean_chunk_size,
+               "Bounds error.");
+        lowest_non_clean[cur_chunk_index] = first_dirty_card;
+      }
+    }
+  }
+}
+
+void
+CardTableModRefBS::
+get_LNC_array_for_space(Space* sp,
+                        jbyte**& lowest_non_clean,
+                        uintptr_t& lowest_non_clean_base_chunk_index,
+                        size_t& lowest_non_clean_chunk_size) {
+
+  int       i        = find_covering_region_containing(sp->bottom());
+  MemRegion covered  = _covered[i];
+  size_t    n_chunks = chunks_to_cover(covered);
+
+  // Only the first thread to obtain the lock will resize the
+  // LNC array for the covered region.  Any later expansion can't affect
+  // the used_at_save_marks region.
+  // (I observed a bug in which the first thread to execute this would
+  // resize, and then it would cause "expand_and_allocates" that would
+  // Increase the number of chunks in the covered region.  Then a second
+  // thread would come and execute this, see that the size didn't match,
+  // and free and allocate again.  So the first thread would be using a
+  // freed "_lowest_non_clean" array.)
+
+  // Do a dirty read here. If we pass the conditional then take the rare
+  // event lock and do the read again in case some other thread had already
+  // succeeded and done the resize.
+  int cur_collection = Universe::heap()->total_collections();
+  if (_last_LNC_resizing_collection[i] != cur_collection) {
+    MutexLocker x(ParGCRareEvent_lock);
+    if (_last_LNC_resizing_collection[i] != cur_collection) {
+      if (_lowest_non_clean[i] == NULL ||
+          n_chunks != _lowest_non_clean_chunk_size[i]) {
+
+        // Should we delete the old?
+        if (_lowest_non_clean[i] != NULL) {
+          assert(n_chunks != _lowest_non_clean_chunk_size[i],
+                 "logical consequence");
+          FREE_C_HEAP_ARRAY(CardPtr, _lowest_non_clean[i]);
+          _lowest_non_clean[i] = NULL;
+        }
+        // Now allocate a new one if necessary.
+        if (_lowest_non_clean[i] == NULL) {
+          _lowest_non_clean[i]                  = NEW_C_HEAP_ARRAY(CardPtr, n_chunks);
+          _lowest_non_clean_chunk_size[i]       = n_chunks;
+          _lowest_non_clean_base_chunk_index[i] = addr_to_chunk_index(covered.start());
+          for (int j = 0; j < (int)n_chunks; j++)
+            _lowest_non_clean[i][j] = NULL;
+        }
+      }
+      _last_LNC_resizing_collection[i] = cur_collection;
+    }
+  }
+  // In any case, now do the initialization.
+  lowest_non_clean                  = _lowest_non_clean[i];
+  lowest_non_clean_base_chunk_index = _lowest_non_clean_base_chunk_index[i];
+  lowest_non_clean_chunk_size       = _lowest_non_clean_chunk_size[i];
+}