Method Merge

tensorflow/core/common_runtime/bfc_allocator.cc:572–602

Merges h1 and h2 when Chunk(h1)->next is h2 and Chunk(h2)->prev is c1. We merge Chunk(h2) into Chunk(h1).

// Merges h1 and h2 when Chunk(h1)->next is h2 and Chunk(h2)->prev is c1.
// We merge Chunk(h2) into Chunk(h1).
void BFCAllocator::Merge(BFCAllocator::ChunkHandle h1,
                         BFCAllocator::ChunkHandle h2) {
  Chunk* c1 = ChunkFromHandle(h1);
  Chunk* c2 = ChunkFromHandle(h2);
  // We can only merge chunks that are not in use.
  CHECK(!c1->in_use() && !c2->in_use());

  // c1's prev doesn't change, still points to the same ptr, and is
  // still not in use.

  // Fix up neighbor pointers
  //
  // c1 <-> c2 <-> c3 should become
  // c1 <-> c3

  BFCAllocator::ChunkHandle h3 = c2->next;
  c1->next = h3;
  CHECK(c2->prev == h1);
  if (h3 != kInvalidChunkHandle) {
    BFCAllocator::Chunk* c3 = ChunkFromHandle(h3);
    c3->prev = h1;
  }

  // Set the new size
  c1->size += c2->size;

  // Pick latest free time.
  c1->freed_at_count = std::max(c1->freed_at_count, c2->freed_at_count);

  DeleteChunk(h2);
}

void BFCAllocator::DeleteChunk(ChunkHandle h) {
  // Delete h and cleanup all state