Hacker News Reader

Comment by diamondlovesyou | Hacker News Reader

> A well-designed interactive GUI application can absolutely interact with the filesystem on its main thread without any impact to responsiveness what-so-ever. You only need threads once you need more CPU time.

The "well-designed" argument here is a bit No True Scotsman, and absolutely not true. Consider a lagging NFS mount. Or old hard drives; a disk seek could take milliseconds!

Real time computing isn't about what is normal or average, it's about the worst case. Filesystem IO can block, therefore you must assume it will.

View on HN

> The "well-designed" argument here is a bit No True Scotsman, and absolutely not true.

This counter arguments can be interpreted as a mere No True Scotsman of "responsiveness", so this is not a very productive line of argument.

Should one be interested in having a discussion like this again, I would suggest strictly establishing what "responsive" means (which is a subjective experience), including defining when a "responsive" application may be "unresponsive" (swapping to disk, no CPU/GPU time, the cat ate the RAM), and evading terms like "well-designed" (I included it in protest of its use in the comment I responded to).

For example, failing to process input or skipping frames in gameplay would be bad, but no one would see a skipped frame in a config menu, and frames cannot even be skipped if there are no frames to be rendered.

> Should one be interested in having a discussion like this again, I would suggest strictly establishing what "responsive" means (which is a subjective experience)

This has been established for years. This is the basis of building real time systems. For example, Flight control systems absolutely must be responsive, no exceptions. What does that mean? That the system is guaranteed to respond to an input within a maximum time limit. POSIX applications may generally give the appearance of being responsive but absolutely are not unless specially configured. There is no upper bound on how long any operation will complete. This will be apparent the minute your entire system starts to choke because of a misbehaving application. Responsive systems have a hard bound on worst case behavior.

Reply on news.ycombinator.com