jdk-24/src/hotspot/share/gc/g1/heapRegion.inline.hpp

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#ifndef SHARE_VM_GC_G1_HEAPREGION_INLINE_HPP
#define SHARE_VM_GC_G1_HEAPREGION_INLINE_HPP

#include "gc/g1/g1BlockOffsetTable.inline.hpp"
#include "gc/g1/g1CollectedHeap.inline.hpp"
#include "gc/g1/g1ConcurrentMarkBitMap.inline.hpp"
#include "gc/g1/heapRegion.hpp"
#include "gc/shared/space.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/atomic.hpp"
#include "runtime/prefetch.inline.hpp"
#include "utilities/align.hpp"

inline HeapWord* G1ContiguousSpace::allocate_impl(size_t min_word_size,
                                                  size_t desired_word_size,
                                                  size_t* actual_size) {
  HeapWord* obj = top();
  size_t available = pointer_delta(end(), obj);
  size_t want_to_allocate = MIN2(available, desired_word_size);
  if (want_to_allocate >= min_word_size) {
    HeapWord* new_top = obj + want_to_allocate;
    set_top(new_top);
    assert(is_aligned(obj) && is_aligned(new_top), "checking alignment");
    *actual_size = want_to_allocate;
    return obj;
  } else {
    return NULL;
  }
}

inline HeapWord* G1ContiguousSpace::par_allocate_impl(size_t min_word_size,
                                                      size_t desired_word_size,
                                                      size_t* actual_size) {
  do {
    HeapWord* obj = top();
    size_t available = pointer_delta(end(), obj);
    size_t want_to_allocate = MIN2(available, desired_word_size);
    if (want_to_allocate >= min_word_size) {
      HeapWord* new_top = obj + want_to_allocate;
      HeapWord* result = Atomic::cmpxchg(new_top, top_addr(), obj);
      // result can be one of two:
      //  the old top value: the exchange succeeded
      //  otherwise: the new value of the top is returned.
      if (result == obj) {
        assert(is_aligned(obj) && is_aligned(new_top), "checking alignment");
        *actual_size = want_to_allocate;
        return obj;
      }
    } else {
      return NULL;
    }
  } while (true);
}

inline HeapWord* G1ContiguousSpace::allocate(size_t min_word_size,
                                             size_t desired_word_size,
                                             size_t* actual_size) {
  HeapWord* res = allocate_impl(min_word_size, desired_word_size, actual_size);
  if (res != NULL) {
    _bot_part.alloc_block(res, *actual_size);
  }
  return res;
}

inline HeapWord* G1ContiguousSpace::allocate(size_t word_size) {
  size_t temp;
  return allocate(word_size, word_size, &temp);
}

inline HeapWord* G1ContiguousSpace::par_allocate(size_t word_size) {
  size_t temp;
  return par_allocate(word_size, word_size, &temp);
}

// Because of the requirement of keeping "_offsets" up to date with the
// allocations, we sequentialize these with a lock.  Therefore, best if
// this is used for larger LAB allocations only.
inline HeapWord* G1ContiguousSpace::par_allocate(size_t min_word_size,
                                                 size_t desired_word_size,
                                                 size_t* actual_size) {
  MutexLocker x(&_par_alloc_lock);
  return allocate(min_word_size, desired_word_size, actual_size);
}

inline HeapWord* G1ContiguousSpace::block_start(const void* p) {
  return _bot_part.block_start(p);
}

inline HeapWord*
G1ContiguousSpace::block_start_const(const void* p) const {
  return _bot_part.block_start_const(p);
}

inline bool HeapRegion::is_obj_dead_with_size(const oop obj, const G1CMBitMap* const prev_bitmap, size_t* size) const {
  HeapWord* addr = (HeapWord*) obj;

  assert(addr < top(), "must be");
  assert(!is_closed_archive(),
         "Closed archive regions should not have references into other regions");
  assert(!is_humongous(), "Humongous objects not handled here");
  bool obj_is_dead = is_obj_dead(obj, prev_bitmap);

  if (ClassUnloadingWithConcurrentMark && obj_is_dead) {
    assert(!block_is_obj(addr), "must be");
    *size = block_size_using_bitmap(addr, prev_bitmap);
  } else {
    assert(block_is_obj(addr), "must be");
    *size = obj->size();
  }
  return obj_is_dead;
}

inline bool
HeapRegion::block_is_obj(const HeapWord* p) const {
  G1CollectedHeap* g1h = G1CollectedHeap::heap();

  if (!this->is_in(p)) {
    assert(is_continues_humongous(), "This case can only happen for humongous regions");
    return (p == humongous_start_region()->bottom());
  }
  if (ClassUnloadingWithConcurrentMark) {
    return !g1h->is_obj_dead(oop(p), this);
  }
  return p < top();
}

inline size_t HeapRegion::block_size_using_bitmap(const HeapWord* addr, const G1CMBitMap* const prev_bitmap) const {
  assert(ClassUnloadingWithConcurrentMark,
         "All blocks should be objects if class unloading isn't used, so this method should not be called. "
         "HR: [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ") "
         "addr: " PTR_FORMAT,
         p2i(bottom()), p2i(top()), p2i(end()), p2i(addr));

  // Old regions' dead objects may have dead classes
  // We need to find the next live object using the bitmap
  HeapWord* next = prev_bitmap->get_next_marked_addr(addr, prev_top_at_mark_start());

  assert(next > addr, "must get the next live object");
  return pointer_delta(next, addr);
}

inline bool HeapRegion::is_obj_dead(const oop obj, const G1CMBitMap* const prev_bitmap) const {
  assert(is_in_reserved(obj), "Object " PTR_FORMAT " must be in region", p2i(obj));
  return !obj_allocated_since_prev_marking(obj) &&
         !prev_bitmap->is_marked((HeapWord*)obj) &&
         !is_open_archive();
}

inline size_t HeapRegion::block_size(const HeapWord *addr) const {
  if (addr == top()) {
    return pointer_delta(end(), addr);
  }

  if (block_is_obj(addr)) {
    return oop(addr)->size();
  }

  return block_size_using_bitmap(addr, G1CollectedHeap::heap()->concurrent_mark()->prev_mark_bitmap());
}

inline void HeapRegion::complete_compaction() {
  // Reset space and bot after compaction is complete if needed.
  reset_after_compaction();
  if (used_region().is_empty()) {
    reset_bot();
  }

  // After a compaction the mark bitmap is invalid, so we must
  // treat all objects as being inside the unmarked area.
  zero_marked_bytes();
  init_top_at_mark_start();

  // Clear unused heap memory in debug builds.
  if (ZapUnusedHeapArea) {
    mangle_unused_area();
  }
}

template<typename ApplyToMarkedClosure>
inline void HeapRegion::apply_to_marked_objects(G1CMBitMap* bitmap, ApplyToMarkedClosure* closure) {
  HeapWord* limit = scan_limit();
  HeapWord* next_addr = bottom();

  while (next_addr < limit) {
    Prefetch::write(next_addr, PrefetchScanIntervalInBytes);
    // This explicit is_marked check is a way to avoid
    // some extra work done by get_next_marked_addr for
    // the case where next_addr is marked.
    if (bitmap->is_marked(next_addr)) {
      oop current = oop(next_addr);
      next_addr += closure->apply(current);
    } else {
      next_addr = bitmap->get_next_marked_addr(next_addr, limit);
    }
  }

  assert(next_addr == limit, "Should stop the scan at the limit.");
}

inline HeapWord* HeapRegion::par_allocate_no_bot_updates(size_t min_word_size,
                                                         size_t desired_word_size,
                                                         size_t* actual_word_size) {
  assert(is_young(), "we can only skip BOT updates on young regions");
  return par_allocate_impl(min_word_size, desired_word_size, actual_word_size);
}

inline HeapWord* HeapRegion::allocate_no_bot_updates(size_t word_size) {
  size_t temp;
  return allocate_no_bot_updates(word_size, word_size, &temp);
}

inline HeapWord* HeapRegion::allocate_no_bot_updates(size_t min_word_size,
                                                     size_t desired_word_size,
                                                     size_t* actual_word_size) {
  assert(is_young(), "we can only skip BOT updates on young regions");
  return allocate_impl(min_word_size, desired_word_size, actual_word_size);
}

inline void HeapRegion::note_start_of_marking() {
  _next_marked_bytes = 0;
  _next_top_at_mark_start = top();
}

inline void HeapRegion::note_end_of_marking() {
  _prev_top_at_mark_start = _next_top_at_mark_start;
  _next_top_at_mark_start = bottom();
  _prev_marked_bytes = _next_marked_bytes;
  _next_marked_bytes = 0;
}

inline bool HeapRegion::in_collection_set() const {
  return G1CollectedHeap::heap()->is_in_cset(this);
}

template <class Closure, bool is_gc_active>
bool HeapRegion::do_oops_on_card_in_humongous(MemRegion mr,
                                              Closure* cl,
                                              G1CollectedHeap* g1h) {
  assert(is_humongous(), "precondition");
  HeapRegion* sr = humongous_start_region();
  oop obj = oop(sr->bottom());

  // If concurrent and klass_or_null is NULL, then space has been
  // allocated but the object has not yet been published by setting
  // the klass.  That can only happen if the card is stale.  However,
  // we've already set the card clean, so we must return failure,
  // since the allocating thread could have performed a write to the
  // card that might be missed otherwise.
  if (!is_gc_active && (obj->klass_or_null_acquire() == NULL)) {
    return false;
  }

  // We have a well-formed humongous object at the start of sr.
  // Only filler objects follow a humongous object in the containing
  // regions, and we can ignore those.  So only process the one
  // humongous object.
  if (!g1h->is_obj_dead(obj, sr)) {
    if (obj->is_objArray() || (sr->bottom() < mr.start())) {
      // objArrays are always marked precisely, so limit processing
      // with mr.  Non-objArrays might be precisely marked, and since
      // it's humongous it's worthwhile avoiding full processing.
      // However, the card could be stale and only cover filler
      // objects.  That should be rare, so not worth checking for;
      // instead let it fall out from the bounded iteration.
      obj->oop_iterate(cl, mr);
    } else {
      // If obj is not an objArray and mr contains the start of the
      // obj, then this could be an imprecise mark, and we need to
      // process the entire object.
      obj->oop_iterate(cl);
    }
  }
  return true;
}

template <bool is_gc_active, class Closure>
bool HeapRegion::oops_on_card_seq_iterate_careful(MemRegion mr,
                                                  Closure* cl) {
  assert(MemRegion(bottom(), end()).contains(mr), "Card region not in heap region");
  G1CollectedHeap* g1h = G1CollectedHeap::heap();

  // Special handling for humongous regions.
  if (is_humongous()) {
    return do_oops_on_card_in_humongous<Closure, is_gc_active>(mr, cl, g1h);
  }
  assert(is_old() || is_archive(), "Wrongly trying to iterate over region %u type %s", _hrm_index, get_type_str());

  // Because mr has been trimmed to what's been allocated in this
  // region, the parts of the heap that are examined here are always
  // parsable; there's no need to use klass_or_null to detect
  // in-progress allocation.

  // Cache the boundaries of the memory region in some const locals
  HeapWord* const start = mr.start();
  HeapWord* const end = mr.end();

  // Find the obj that extends onto mr.start().
  // Update BOT as needed while finding start of (possibly dead)
  // object containing the start of the region.
  HeapWord* cur = block_start(start);

#ifdef ASSERT
  {
    assert(cur <= start,
           "cur: " PTR_FORMAT ", start: " PTR_FORMAT, p2i(cur), p2i(start));
    HeapWord* next = cur + block_size(cur);
    assert(start < next,
           "start: " PTR_FORMAT ", next: " PTR_FORMAT, p2i(start), p2i(next));
  }
#endif

  const G1CMBitMap* const bitmap = g1h->concurrent_mark()->prev_mark_bitmap();
  do {
    oop obj = oop(cur);
    assert(oopDesc::is_oop(obj, true), "Not an oop at " PTR_FORMAT, p2i(cur));
    assert(obj->klass_or_null() != NULL,
           "Unparsable heap at " PTR_FORMAT, p2i(cur));

    size_t size;
    bool is_dead = is_obj_dead_with_size(obj, bitmap, &size);

    cur += size;
    if (!is_dead) {
      // Process live object's references.

      // Non-objArrays are usually marked imprecise at the object
      // start, in which case we need to iterate over them in full.
      // objArrays are precisely marked, but can still be iterated
      // over in full if completely covered.
      if (!obj->is_objArray() || (((HeapWord*)obj) >= start && cur <= end)) {
        obj->oop_iterate(cl);
      } else {
        obj->oop_iterate(cl, mr);
      }
    }
  } while (cur < end);

  return true;
}

#endif // SHARE_VM_GC_G1_HEAPREGION_INLINE_HPP