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1. SFS: smart OS Scheduling for Serverless Functions

   Fu, Yuqi ; Liu, Li ; Wang, Haoliang ; Cheng, Yue ; Chen, Songqing ( November 2022 , International Conference for High Performance Computing Networking Storage and Analysis)

   Serverless computing enables a new way of building and scaling cloud applications by allowing developers to write fine-grained serverless or cloud functions. The execution duration of a cloud function is typically short---ranging from a few milliseconds to hundreds of seconds. However, due to resource contentions caused by public clouds' deep consolidation, the function execution duration may get significantly prolonged and fail to accurately account for the function's true resource usage. We observe that the function duration can be highly unpredictable with huge amplification of more than 50× for an open-source FaaS platform (OpenLambda). Our experiments show that the OS scheduling policy of cloud functions' host server can have a crucial impact on performance. The default Linux scheduler, CFS (Completely Fair Scheduler), being oblivious to workloads, frequently context-switches short functions, causing a turnaround time that is much longer than their service time. We propose SFS (Smart Function Scheduler), which works entirely in the user space and carefully orchestrates existing Linux FIFO and CFS schedulers to approximate Shortest Remaining Time First (SRTF). SFS uses two-level scheduling that seamlessly combines a new FILTER policy with Linux CFS, to trade off increased duration of long functions for significant performance improvement for short functions. Wemore »implement SFS in the Linux user space and port it to OpenLambda. Evaluation results show that SFS significantly improves short functions' duration with a small impact on relatively longer functions, compared to CFS.« less
2. Implications of Alternative Serverless Application Control Flow Methods

   https://doi.org/10.1145/3493651.3493668  

   Quinn, Sterling ; Cordingly, Robert ; Lloyd, Wes ( December 2021 , WoSC '21: Proceedings of the Seventh International Workshop on Serverless Computing (WoSC7) 2021)

   Function-as-a-Service or FaaS is a popular delivery model of serverless computing where developers upload code to be executed in the cloud as short running stateless functions. Using smaller functions to decompose processing of larger tasks or workflows introduces the question of how to instrument application control flow to orchestrate an overall task or workflow. In this paper, we examine implications of using different methods to orchestrate the control flow of a serverless data processing pipeline composed as a set of independent FaaS functions. We performed experiments on the AWS Lambda FaaS platform and compared how four different patterns of control flow impact the cost and performance of the pipeline. We investigate control flow using client orchestration, microservice controllers, event-based triggers, and state-machines. Overall, we found that asynchronous methods led to lower orchestration costs, and that event-based orchestration incurred a performance penalty.
3. Archipelago: A Scalable Low-Latency Serverless Platform

   Singhvi, A ; Houck, K ; Balasubramanian, A ; Shaikh, Mohammed S ; Venkataraman, S ; Akella, A ( November 2019 , ArXivorg)

   The increased use of micro-services to build web applications has spurred the rapid growth of Function-as-a-Service (FaaS) or serverless computing platforms. While FaaS simplifies provisioning and scaling for application developers, it introduces new challenges in resource management that need to be handled by the cloud provider. Our analysis of popular serverless workloads indicates that schedulers need to handle functions that are very short-lived, have unpredictable arrival patterns, and require expensive setup of sandboxes. The challenge of running a large number of such functions in a multi-tenant cluster makes existing scheduling frameworks unsuitable. We present Archipelago, a platform that enables low latency request execution in a multi-tenant serverless setting. Archipelago views each application as a DAG of functions, and every DAG in associated with a latency deadline. Archipelago achieves its per-DAG request latency goals by: (1) partitioning a given cluster into a number of smaller worker pools, and associating each pool with a semi-global scheduler (SGS), (2) using a latency-aware scheduler within each SGS along with proactive sandbox allocation to reduce overheads, and (3) using a load balancing layer to route requests for different DAGs to the appropriate SGS, and automatically scale the number of SGSs per DAG. Our testbed resultsmore »show that Archipelago meets the latency deadline for more than 99% of realistic application request workloads, and reduces tail latencies by up to 36X compared to state-of-the-art serverless platforms.« less
4. STOIC: Serverless TeleOperable Hybrid Cloud for Machine Learning Applications on Edge Device

   Zhang, M ; Krintz, C ; Wolski, R. ( March 2020 , International Workshop on Smart Edge Computing and Networking)

   Serverless computing is a promising new event- driven programming model that was designed by cloud vendors to expedite the development and deployment of scalable web services on cloud computing systems. Using the model, developers write applications that consist of simple, independent, stateless functions that the cloud invokes on-demand (i.e. elastically), in response to system-wide events (data arrival, messages, web requests, etc.). In this work, we present STOIC (Serverless TeleOperable HybrId Cloud), an application scheduling and deployment system that extends the serverless model in two ways. First, it uses the model in a distributed setting and schedules application functions across multiple cloud systems. Second, STOIC sup- ports serverless function execution using hardware acceleration (e.g. GPU resources) when available from the underlying cloud system. We overview the design and implementation of STOIC and empirically evaluate it using real-world machine learning applications and multi-tier (e.g. edge-cloud) deployments. We find that STOIC’s combined use of edge and cloud resources is able to outperform using either cloud in isolation for the applications and datasets that we consider.
5. Transactional Causal Consistency for Serverless Computing

   https://doi.org/10.1145/3318464.3389710  

   Wu, Chenggang ; Sreekanti, Vikram ; Hellerstein, Joseph M. ( May 2020 , SIGMOD '20: Proceedings of the 2020 ACM SIGMOD International Conference on Management of Data)

   We consider the setting of serverless Function-as-a-Service (FaaS) platforms, where storage services are disaggregated from the machines that support function execution. FaaS applications consist of compositions of functions, each of which may run on a separate machine and access remote storage. The challenge we address is improving I/O latency in this setting while also providing application-wide consistency. Previous work has explored providing causal consistency for individual I/Os by carefully managing the versions stored in a client-side data cache. In our setting, a single application may execute multiple functions across different nodes, and therefore issue interrelated I/Os to multiple distinct caches. This raises the challenge of Multisite Transactional Causal Consistency (MTCC): the ability to provide causal consistency for all I/Os within a given transaction even if it runs across multiple physical sites. We present protocols for MTCC implemented in a system called HYDROCACHE. Our evaluation demonstrates orders-of-magnitude performance improvements due to caching, while also protecting against consistency anomalies that otherwise arise frequently.