io_uring without readahead, and a Tektronix refurbishment

What's this about?

Two systems posts. One on using io_uring without kernel readahead. One on refurbishing a Tektronix TDS7104 oscilloscope.

What is io_uring and why disable readahead?

io_uring is Linux's modern asynchronous I/O interface: you submit operations into a shared ring buffer and collect completions from another, avoiding a syscall per operation. It is how high-performance storage code is written now. Readahead is the kernel guessing you will want the next block and fetching it early — excellent for sequential reads, wasteful for genuinely random access, where you pay to load data you will never touch. Turning it off is the right call when you know your access pattern better than the kernel's heuristic does.

Why is it worth noticing?

1. Storage performance work is having a moment for the same reason memory optimisation is — the hardware got expensive.
2. The Tektronix piece is from tomverbeure, whose hardware teardowns are consistently the best of the genre.
3. Grouped because both are the kind of careful systems work that this audience reliably rewards.