src/hotspot/share/jfr/leakprofiler/chains/dfsClosure.cpp

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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#include "jfr/leakprofiler/chains/dfsClosure.hpp"
#include "jfr/leakprofiler/chains/edge.hpp"
#include "jfr/leakprofiler/chains/edgeStore.hpp"
#include "jfr/leakprofiler/chains/jfrbitset.hpp"
#include "jfr/leakprofiler/chains/rootSetClosure.hpp"
#include "jfr/leakprofiler/utilities/granularTimer.hpp"
#include "jfr/leakprofiler/utilities/rootType.hpp"
#include "jfr/leakprofiler/utilities/unifiedOopRef.inline.hpp"
#include "memory/iterator.inline.hpp"
#include "memory/resourceArea.hpp"
#include "oops/access.inline.hpp"
#include "oops/oop.inline.hpp"
#include "utilities/align.hpp"

UnifiedOopRef DFSClosure::_reference_stack[max_dfs_depth];

void DFSClosure::find_leaks_from_edge(EdgeStore* edge_store,
                                      JFRBitSet* mark_bits,
                                      const Edge* start_edge) {
  assert(edge_store != nullptr, "invariant");
  assert(mark_bits != nullptr," invariant");
  assert(start_edge != nullptr, "invariant");

  // Depth-first search, starting from a BFS edge
  DFSClosure dfs(edge_store, mark_bits, start_edge);
  start_edge->pointee()->oop_iterate(&dfs);
}

void DFSClosure::find_leaks_from_root_set(EdgeStore* edge_store,
                                          JFRBitSet* mark_bits) {
  assert(edge_store != nullptr, "invariant");
  assert(mark_bits != nullptr, "invariant");

  // Mark root set, to avoid going sideways
  DFSClosure dfs(edge_store, mark_bits, nullptr);
  dfs._max_depth = 1;
  RootSetClosure<DFSClosure> rs(&dfs);
  rs.process();

  // Depth-first search
  dfs._max_depth = max_dfs_depth;
  dfs._ignore_root_set = true;
  rs.process();
}

DFSClosure::DFSClosure(EdgeStore* edge_store, JFRBitSet* mark_bits, const Edge* start_edge)
  :_edge_store(edge_store), _mark_bits(mark_bits), _start_edge(start_edge),
  _max_depth(max_dfs_depth), _depth(0), _ignore_root_set(false) {
}

void DFSClosure::closure_impl(UnifiedOopRef reference, const oop pointee) {
  assert(pointee != nullptr, "invariant");
  assert(!reference.is_null(), "invariant");

  if (GranularTimer::is_finished()) {
    return;
  }

  if (_depth == 0 && _ignore_root_set) {
    // Root set is already marked, but we want
    // to continue, so skip is_marked check.
    assert(_mark_bits->is_marked(pointee), "invariant");
    _reference_stack[_depth] = reference;
  } else {
    if (_mark_bits->is_marked(pointee)) {
      return;
    }
    _mark_bits->mark_obj(pointee);
    _reference_stack[_depth] = reference;
    // is the pointee a sample object?
    if (pointee->mark().is_marked()) {
      add_chain();
    }
  }
  assert(_max_depth >= 1, "invariant");
  if (_depth < _max_depth - 1) {
    _depth++;
    pointee->oop_iterate(this);
    assert(_depth > 0, "invariant");
    _depth--;
  }
}

void DFSClosure::add_chain() {
  const size_t array_length = _depth + 2;

  ResourceMark rm;
  Edge* const chain = NEW_RESOURCE_ARRAY(Edge, array_length);
  size_t idx = 0;

  // aggregate from depth-first search
  for (size_t i = 0; i <= _depth; i++) {
    const size_t next = idx + 1;
    const size_t depth = _depth - i;
    chain[idx++] = Edge(&chain[next], _reference_stack[depth]);
  }
  assert(_depth + 1 == idx, "invariant");
  assert(array_length == idx + 1, "invariant");

  // aggregate from breadth-first search
  if (_start_edge != nullptr) {
    chain[idx++] = *_start_edge;
  } else {
    chain[idx - 1] = Edge(nullptr, chain[idx - 1].reference());
  }
  _edge_store->put_chain(chain, idx + (_start_edge != nullptr ? _start_edge->distance_to_root() : 0));
}

void DFSClosure::do_oop(oop* ref) {
  assert(ref != nullptr, "invariant");
  assert(is_aligned(ref, HeapWordSize), "invariant");
  const oop pointee = HeapAccess<AS_NO_KEEPALIVE>::oop_load(ref);
  if (pointee != nullptr) {
    closure_impl(UnifiedOopRef::encode_in_heap(ref), pointee);
  }
}

void DFSClosure::do_oop(narrowOop* ref) {
  assert(ref != nullptr, "invariant");
  assert(is_aligned(ref, sizeof(narrowOop)), "invariant");
  const oop pointee = HeapAccess<AS_NO_KEEPALIVE>::oop_load(ref);
  if (pointee != nullptr) {
    closure_impl(UnifiedOopRef::encode_in_heap(ref), pointee);
  }
}

void DFSClosure::do_root(UnifiedOopRef ref) {
  assert(!ref.is_null(), "invariant");
  const oop pointee = ref.dereference();
  assert(pointee != nullptr, "invariant");
  closure_impl(ref, pointee);
}