POLCA: Power Oversubscription in LLM Cloud Providers
Pratyush Patel Esha Choukse Chaojie Zhang Íñigo Goiri Brijesh Warrier Nithish Mahalingam Ricardo Bianchini
Recent innovation in large language models (LLMs), and their myriad use-cases
have rapidly driven up the compute capacity demand for datacenter GPUs. Several
cloud providers and other enterprises have made substantial plans of growth in
their datacenters to support these new workloads. One of the key bottleneck
resources in datacenters is power, and given the increasing model sizes of
LLMs, they are becoming increasingly power intensive. In this paper, we show
that there is a significant opportunity to oversubscribe power in LLM clusters.
Power oversubscription improves the power efficiency of these datacenters,
allowing more deployable servers per datacenter, and reduces the deployment
time, since building new datacenters is slow.
  We extensively characterize the power consumption patterns of a variety of
LLMs and their configurations. We identify the differences between the
inference and training power consumption patterns. Based on our analysis of
these LLMs, we claim that the average and peak power utilization in LLM
clusters for inference should not be very high. Our deductions align with the
data from production LLM clusters, revealing that inference workloads offer
substantial headroom for power oversubscription. However, the stringent set of
telemetry and controls that GPUs offer in a virtualized environment, makes it
challenging to have a reliable and robust power oversubscription mechanism.
  We propose POLCA, our framework for power oversubscription that is robust,
reliable, and readily deployable for GPU clusters. Using open-source models to
replicate the power patterns observed in production, we simulate POLCA and
demonstrate that we can deploy 30% more servers in the same GPU cluster for
inference, with minimal performance loss