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Performance optimization of mobile systems is critical for achieving responsive user experiences. However, accurately measuring the effects of such optimizations is challenging. We found that real-world mobile workloads exhibit a flat profile, invoking thousands of short-lived routines that contribute evenly to overall performance with no dominant bottlenecks. Sampling-based profilers such as perf struggle in this setting: skid, shadow effects, and incomplete function coverage can yield systematically incorrect results, not just high variance. We present Blink, a lightweight instrumentation framework that provides robust coverage for short-lived routines while maintaining low overhead. Blink inserts instrumentation into functions, enabling precise measurements. We show that Blink achieves 99.999% accuracy while incurring 1% overhead. Deployed in a variety of use cases at Huawei, Blink offers a practical and reliable alternative for mobile compiler performance analysis.