3 ms·

Possibly... All I can surmise is that the OP may think disks are addressed in a memory-mapped fashion and hence may be subject to page-faults for some reason.

• tonyarkles 7y ago
  Reading that generously and since we’re talking about abstractions... reading from disk via mmap does work via page faults! Except... it’s a layer up. Doing random reads on an mmap’d file will likely have terrible performance until those pages have been cached, but one layer down there’s no guarantee that sequential reads from an mmap’d file are going to be sequential reads from disk! (Because the file isn’t guaranteed to be laid out sequentially on disk) Others in this discussion have talked about some abstractions being perfect and a consumer not needing to understand the layer beneath; I strongly disagree. Ultimately, the physical reality of the machine will come into play (disk, RAM, caches, network, CPU etc), and I am generally uncomfortable if I don’t have a solid feel for how the high-level operations in an abstraction are going to use those resources.