message: Add in a comment that I forgot to add to a previous commit; NFC.
diff: @@ -136,6 +136,10 @@ DotInLlvmIrProfitable ProfitableToImplementDotInLlvmIr(
  const int64 kReductionDimensionThresholdBytes = 8 * 1024;
  const bool single_threaded_eigen =
  !dot.GetModule()->config().debug_options().xla_cpu_multi_thread_eigen();
  +
  + // This is the point at which it is better to call into Eigen and shard the
  + // dot across multiple worker threads. This is a rough estimate by running
  + // a matmult benchmark on my local machine, and it can be tuned further.
  const int64 kMaxSingleThreadedFlops = 16 * 1024;
  const int64 M = result_shape.dimensions(0);
  