It's Not the Storage : Exposing Linux Kernel Bottlenecks in Page Fault Handling on NVMe SSD-backed Systems

The long latencies of major page faults are often blamed on slow storage, but our study shows that with modern locally attached NVMe SSDs used as swap space, the real culprit is the Linux kernel itself. Indeed, kernel overhead from page table walks, swap cache lookups, block-layer bookkeeping, and interrupt handling frequently exceed the time spent on disk I/O. To explore this, we introduce a lightweight measurement methodology that accurately attributes page fault costs across kernel, I/O, and user-level components. Using representative workloads and microbenchmarks on a single-socket desktop machine, we show that NVMe SSD bandwidth is rarely the bottleneck, and that Linux’s default readahead policy can unpredictably amplify latency. Our findings challenge common assumptions, reveal hidden kernel costs, and point toward opportunities for redesigning page fault handling for modern systems.