Scott Shenker

A longstanding performance challenge in datacenter-based applications is how to efficiently handle incoming client requests that spawn many very short (μs scale) jobs that must be handled with high throughput and low tail latency. When no assumptions are made about the duration of individual jobs, or even about the distribution of their durations, this requires blind scheduling with frequent and efficient preemption, which is not scalably supported for μs-level tasks. We present Tiny Quanta (TQ), a system that enables efficient blind scheduling of μs-level workloads. TQ performs fine-grained preemptive scheduling and does so with high performance via a novel combination of two mechanisms: forced multitasking and two-level scheduling. Evaluations with a wide variety of μs-level workloads show that TQ achieves low tail latency while sustaining 1.2x to 6.8x the throughput of prior blind scheduling systems.

The goal of this short document is to explain why recent developments in the Internet's infrastructure are problematic. As context, we note that the Internet was originally designed to provide a simple universal service - global end-to-end packet delivery - on which a wide variety of end-user applications could be built. The early Internet supported this packet-delivery service via an interconnected collection of commercial Internet Service Providers (ISPs) that we will refer to collectively as the "public Internet." The Internet has fulfilled its packet-delivery mission far beyond all expectations and is now the dominant global communications infrastructure. By providing a level playing field on which new applications could be deployed, the Internet has enabled a degree of innovation that no one could have foreseen. To improve performance for some common applications, "enhancements" such as caching (as in content …

Cloud providers offer spot instances alongside on-demand instances to optimize resource utilization. While economically appealing, spot instances’ preemptible nature causes them ill-suited for deadline-sensitive jobs. To allow jobs to meet deadlines while leveraging spot instances, we propose a simple idea: use on-demand instances judiciously as a backup resource. However, due to the unpredictable spot instance availability, determining when to switch between spot and on-demand to minimize cost requires careful policy design. In this paper, we first provide an in-depth characterization of spot instances (eg, availability, pricing, duration), and develop a basic theoretical model to examine the worst and average-case behaviors of baseline policies (eg, greedy). The model serves as a foundation to motivate our design of a simple and effective policy, Uniform Progress, which is parameter-free and requires no …

Reconfiguring the network stack allows applications to specialize the implementations of communication libraries depending on where they run, the requests they serve, and the performance they need to provide. Specializing applications in this way is challenging because developers need to choose the libraries they use when writing a program and cannot easily change them at runtime. This paper introduces Bertha, which allows these choices to be changed at runtime without limiting developer flexibility in the choice of network and communication functions. Bertha allows applications to safely use optimized communication primitives (including ones with deployment limitations) without limiting deployability. Our evaluation shows cases where this results in 16x higher throughput and 63% lower latency than current portable approaches while imposing minimal overheads when compared to a hand-optimized versions that use deployment-specific communication primitives.

Looking past inessential complexities to explain the Internet's simple yet daring design.

There have been many recent advances in enforcing finegrained access control for database-backed applications. However, operators face significant challenges both before and after an enforcement mechanism has been deployed. We identify three such challenges beyond enforcement and discuss possible solutions.

To comply with the increasing number of government regulations about data placement and processing, and to protect themselves against major cloud outages, many users want the ability to easily migrate their workloads between clouds. In this paper we propose doing so not by imposing uniform and comprehensive standards, but by creating a fine-grained two-sided market via an intercloud broker. These brokers will allow users to view the cloud ecosystem not just as a collection of individual and largely incompatible clouds but as a more integrated Sky of Computing. We describe the design and implementation of an intercloud broker, named SkyPilot, evaluate its benefits, and report on its real-world usage.

Cellular operators today know both the identity and location of their mobile subscribers and hence can easily profile users based on this information. Given this status quo, we aim to design a cellular architecture that protects the location privacy of users from their cellular providers. The fundamental challenge in this is reconciling privacy with an operator's need to provide services based on a user's identity (eg, post-pay, QoS and service classes, lawful intercept, emergency services, forensics).