Scoped identifiers for efficient bit aligned logging

Detailed diagnostic data is a prerequisite for debugging problems and understanding runtime performance in distributed wireless embedded systems. Severe bandwidth limitations, tight timing constraints, and limited program text space hinder the application of standard diagnostic tools within this domain. This work introduces the Log Instrumentation Specification (LIS), which provides a high level logging interface to developers and is able to create extremely compact diagnostic logs. LIS uses a token scoping technique to aggressively compact identifiers that are packed into bit aligned log buffers. LIS is evaluated in the context of recording call traces within a network of wireless sensor nodes. Our evaluation shows that logs generated using LIS require less than 50% of the bandwidth utilized by alternate logging mechanisms. Through microbench-marking of a complete LIS implementation for the TinyOS operating system, we demonstrate that LIS can comfortably fit onto low-end embedded systems. By significantly reducing log bandwidth, LIS enables extraction of a more complete picture of runtime behavior from distributed wireless embedded systems.