As a first demonstration of PCOS, we developed a PC-based access pattern classification technique (PCC) for buffer cache management. PCC allows the operating system to correlate the I/O operations with the program context in which they are issued via the PCs of the call instructions that trigger the I/O requests. This correlation allows the operating system to classify I/O access pattern on a per-call-site basis which achieves significantly better accuracy than previous per-file or per-application classification techniques.
We have also developed a PC-based technique (PCAP) for power management that dynamically learns the application I/O access patterns and associated disk idle times to predict when an I/O device can be shut down to save energy. PCAP uses path-based correlation to observe a particular sequence of I/O triggering instructions leading to each idle period, and accurately predicts future occurrences of that idle period.