message: [TF:XLA] Add clarification to the DFS scheduler.
diff: @@ -457,6 +457,13 @@ StatusOr<std::vector<const HloInstruction*>> DFSMemoryScheduler(
  extra_users[hlo] += extra_users[operand];
  total_sizes[hlo] += total_sizes[operand];
  }
  + // total_sizes[hlo] transitively includes the sizes of all nodes that
  + // lead to it. But computation is a DAG, so we are double-counting nodes,
  + // which can lead to overflows for large programs.
  + // cumulative_total_size caps the size to prevent overflows.
  + // NOTE(dimvar): this is quite ugly and should be changed. It's unclear
  + // why we care about transitive sizes; when scheduling a node, its input
  + // and output buffers should be all that matters, not its "history".
  total_sizes[hlo] = std::min(total_sizes[hlo], cumulative_total_size);
  }
  CHECK_EQ(extra_users.size(), computation.instruction_count());
  