  Deep learning-based recommender models (DLRMs) have become an essential
component of many modern recommender systems. Several companies are now
building large compute clusters reserved only for DLRM training, driving new
interest in cost- and time- saving optimizations. The systems challenges faced
in this setting are unique; while typical deep learning training jobs are
dominated by model execution, the most important factor in DLRM training
performance is often online data ingestion.
  In this paper, we explore the unique characteristics of this data ingestion
problem and provide insights into DLRM training pipeline bottlenecks and
challenges. We study real-world DLRM data processing pipelines taken from our
compute cluster at Netflix to observe the performance impacts of online
ingestion and to identify shortfalls in existing pipeline optimizers. We find
that current tooling either yields sub-optimal performance, frequent crashes,
or else requires impractical cluster re-organization to adopt. Our studies lead
us to design and build a new solution for data pipeline optimization, InTune.
  InTune employs a reinforcement learning (RL) agent to learn how to distribute
the CPU resources of a trainer machine across a DLRM data pipeline to more
effectively parallelize data loading and improve throughput. Our experiments
show that InTune can build an optimized data pipeline configuration within only
a few minutes, and can easily be integrated into existing training workflows.
By exploiting the responsiveness and adaptability of RL, InTune achieves higher
online data ingestion rates than existing optimizers, thus reducing idle times
in model execution and increasing efficiency. We apply InTune to our real-world
cluster, and find that it increases data ingestion throughput by as much as
2.29X versus state-of-the-art data pipeline optimizers while also improving
both CPU & GPU utilization.
