[otterley]

“Linux may cache the filesystem data” means there’s a non-zero likelihood that the data in memory unless you dropped caches right before you began the benchmark. You don’t have to explicitly load it into memory for this to be true. What’s more, unless you are in charge of how memory is used, the kernel is going to make its own decisions as to what to cache and what to evict, which can make benchmarks unreproducible.

It’s important to know what you are benchmarking before you start and to control for extrinsic factors as explicitly as possible.