Time Capsule
Kun Suo, Jia Rao, Luwei Cheng, Francis C. M. Lau · 2016
Latency monitoring is important for improving user experience and guaranteeing quality-of-service (QoS). Virtualized systems, which have complex I/O stacks spanning multiple layers and often with unpredictable performance, present more challenges in monitoring packet latency and diagnosing performance abnormalities compared to traditional systems. Existing tools either trace network latency at a coarse granularity, or incur considerable overhead, or lack the ability to trace across different boundaries in virtualized environments. To address this issue, we propose Time Capsule (TC), an in-band profiler to trace packet level latency in virtualized systems with acceptable overhead. TC timestamps packets at predefined tracepoints and embeds the timing information into packet payloads. TC decomposes and attributes network latency to various layers in the virtualized network stack, which can help monitor network latency, identify bottlenecks, and locate performance problems.