To increase utilization, datacenter schedulers often overcommit resources where the sum of resources allocated to the tasks on a machine exceeds its physical capacity. Setting the right level of overcommitment is a challenging problem: low overcommitment leads to wasted resources, while high overcommitment leads to task performance degradation. In this paper, we take a first principles approach to designing and evaluating overcommit policies by asking a basic question: assuming complete knowledge of each task's future resource usage, what is the safest overcommit policy that yields the highest utilization? We call this policy the peak oracle. We then devise practical overcommit policies that mimic this peak oracle by predicting future machine resource usage. We simulate our overcommit policies using the recently-released Google cluster trace, and show that they result in higher utilization and less overcommit errors than policies based on per-task allocations. We also deploy these policies to machines inside Google's datacenters serving its internal production workload. We show that our overcommit policies increase these machines' usable CPU capacity by 10-16% compared to no overcommitment.

Non-uniform memory access (NUMA) has been extensively studied at the machine level but few studies have examined NUMA optimizations at the cluster level. This paper introduces a holistic NUMA-aware scheduling policy that combines both machine-level and cluster-level NUMA-aware optimizations. We evaluate our holistic NUMA-aware scheduling policy on Google's production cluster trace with a cluster scheduling simulator that measures the impact of NUMAaware scheduling under two scheduling algorithms, Best Fit and Enhanced PVM (E-PVM). While our results highlight that a holistic NUMA-aware scheduling policy substantially increases the proportion of NUMA-fit tasks by 22.0% and 25.6% for both the Best Fit and E-PVM scheduling algorithms, respectively, there is a non-trivial tradeoff between cluster job packing efficiency and NUMA-fitness for the E-PVM algorithm under certain circumstances.

Performance isolation is a key challenge in cloud computing. Unfortunately, Linux has few defenses against performance interference in shared resources such as processor caches and memory buses, so applications in a cloud can experience unpredictable performance caused by other programs' behavior.