Files, Memory Mapping, and Asynchronous I/O

Status Draft outlineSection Operating Systems and Execution

Buffered reads, memory mappings, and asynchronous requests expose different interfaces to the same storage and page-cache machinery.

Planned model

Trace data from a file through page cache, copying, faults, queued requests, completion, dirty pages, and writeback.

Questions

• When does mmap avoid copying, and when does it merely defer work to faults?
• What does asynchronous I/O make asynchronous?
• Which durability guarantees require explicit synchronization?

Exercise

Choose an I/O design for replaying a large append-only log while bounding stalls and memory use.