view src/hotspot/share/gc/g1/g1SATBMarkQueueFilter.cpp @ 51278:d56dd9798d54

8208611: Refactor SATBMarkQueue filtering to allow GC-specific filters Summary: Add SATBMarkQueueFilter. Reviewed-by: tschatzl, eosterlund, rkennke
author kbarrett
date Wed, 01 Aug 2018 19:14:04 -0400
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 * published by the Free Software Foundation.
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 * 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.
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#include "precompiled.hpp"
#include "gc/g1/g1CollectedHeap.inline.hpp"
#include "gc/g1/g1SATBMarkQueueFilter.hpp"
#include "gc/g1/heapRegion.hpp"
#include "gc/g1/satbMarkQueue.hpp"
#include "oops/oop.hpp"
#include "utilities/debug.hpp"
#include "utilities/globalDefinitions.hpp"

G1SATBMarkQueueFilter::G1SATBMarkQueueFilter(G1CollectedHeap* g1h) : _g1h(g1h) {}

// Return true if a SATB buffer entry refers to an object that
// requires marking.
// The entry must point into the G1 heap.  In particular, it must not
// be a NULL pointer.  NULL pointers are pre-filtered and never
// inserted into a SATB buffer.
// An entry that is below the NTAMS pointer for the containing heap
// region requires marking. Such an entry must point to a valid object.
// An entry that is at least the NTAMS pointer for the containing heap
// region might be any of the following, none of which should be marked.
// * A reference to an object allocated since marking started.
//   According to SATB, such objects are implicitly kept live and do
//   not need to be dealt with via SATB buffer processing.
// * A reference to a young generation object. Young objects are
//   handled separately and are not marked by concurrent marking.
// * A stale reference to a young generation object. If a young
//   generation object reference is recorded and not filtered out
//   before being moved by a young collection, the reference becomes
//   stale.
// * A stale reference to an eagerly reclaimed humongous object.  If a
//   humongous object is recorded and then reclaimed, the reference
//   becomes stale.
// The stale reference cases are implicitly handled by the NTAMS
// comparison. Because of the possibility of stale references, buffer
// processing must be somewhat circumspect and not assume entries
// in an unfiltered buffer refer to valid objects.

static inline bool requires_marking(const void* entry, G1CollectedHeap* g1h) {
  // Includes rejection of NULL pointers.
         "Non-heap pointer in SATB buffer: " PTR_FORMAT, p2i(entry));

  HeapRegion* region = g1h->heap_region_containing(entry);
  assert(region != NULL, "No region for " PTR_FORMAT, p2i(entry));
  if (entry >= region->next_top_at_mark_start()) {
    return false;

  assert(oopDesc::is_oop(oop(entry), true /* ignore mark word */),
         "Invalid oop in SATB buffer: " PTR_FORMAT, p2i(entry));

  return true;

static inline bool discard_entry(const void* entry, G1CollectedHeap* g1h) {
  return !requires_marking(entry, g1h) || g1h->is_marked_next((oop)entry);

// Workaround for not yet having std::bind.
class G1SATBMarkQueueFilterFn {
  G1CollectedHeap* _g1h;

  G1SATBMarkQueueFilterFn(G1CollectedHeap* g1h) : _g1h(g1h) {}

  // Return true if entry should be filtered out (removed), false if
  // it should be retained.
  bool operator()(const void* entry) const {
    return discard_entry(entry, _g1h);

void G1SATBMarkQueueFilter::filter(SATBMarkQueue* queue) {