Container networking, which provides connectivity among containers on multiple hosts, is crucial to building and scaling container-based microservices. While overlay networks are widely adopted in production systems, they cause significant performance degradation in both throughput and latency compared to physical networks. This paper seeks to understand the bottlenecks of in-kernel networking when running container overlay networks. Through profiling and code analysis, we find that a prolonged data path, due to packet transformation in overlay networks, is the culprit of performance loss. Furthermore, existing scaling techniques in the Linux network stack are ineffective for parallelizing the prolonged data path of a single network flow.We propose Falcon, a fast and balanced container networking approach to scale the packet processing pipeline in overlay networks. Falcon pipelines software interrupts associated with different network devices of a single flow on multiple cores, thereby preventing execution serialization of excessive software interrupts from overloading a single core. Falcon further supports multiple network flows by effectively multiplexing and balancing software interrupts of different flows among available cores. We have developed a prototype of Falcon in Linux. Our evaluation with both micro-benchmarks and real-world applications demonstrates the effectiveness of Falcon, with significantly improved performance (by 300% for web serving) and reduced tail latency (by 53% for data caching).

Container storage commonly relies on overlay file systems to interpose read-only container images upon backing file systems. While being transparent to and compatible with most existing backing file systems, the overlay file-system approach imposes nontrivial I/O overhead to containerized applications, especially for writes: To write a file originating from a read-only container image, the whole file will be copied to a separate, writable storage layer, resulting in long write latency and inefficient use of container storage. In this paper, we present BAOverlay, a lightweight, block-accessible overlay file system: Equipped with a new block-accessibility attribute, BAOverlay not only exploits the benefit of using an asynchronous copy-on-write mechanism for fast file updates but also enables a new file format for efficient use of container storage space. We have developed a prototype of BAOverlay upon Linux Ext4. Our evaluation with both micro-benchmarks and real-world applications demonstrates the effectiveness of BAOverlay with improved write performance and on-demand container storage usage. CCS CONCEPTS • Information systems → Storage virtualization; • Software and its engineering → File systems management.

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