Optimizing the utilization of Large Language Models via schedule optimization: an exploratory study

Background: Large Language Models (LLMs) have gained significant attention in machine-learning-as-a-service (MLaaS) offerings. In-context learning (ICL) is a technique that guides LLMs towards accurate query processing by providing additional information. However, longer prompts lead to higher costs of LLM service, creating a performance-cost trade-off. Aims: We aim to investigate the potential of combining schedule optimization with ICL to optimize LLM utilization. Method: We conduct an exploratory study. First, we consider the performance-cost trade-off in LLM utilization as a multi-objective optimization problem, aiming to select the most suitable prompt template for each LLM job to maximize accuracy (the percentage of correctly processed jobs) and minimize invocation cost. Next, we investigate three methods for prompt performance prediction to address the challenge of evaluating the accuracy objective in the fitness function, as the result can only be determined after submitting the job to the LLM. Finally, we apply widely used search-based techniques and evaluate their effectiveness. Results: The results indicate that the machine learning-based technique is an effective approach for prompt performance prediction and fitness function calculation. Schedule optimization can achieve higher accuracy or lower cost by selecting a suitable prompt template for each job, compared to simply submitting all jobs using a single prompt template, e.g., saving costs from 21.33% to 86.92% in our experiments on LLM-based log parsing. However, the performance of the evaluated search-based techniques varies across different instances and metrics, with no single technique consistently outperforming the others. Conclusions: This study demonstrates the potential of combining schedule optimization with ICL to improve the utilization of LLMs. However, there is still ample room for improving the searched-based techniques and prompt performance prediction techniques for more cost-effective LLM utilization.