[jules]

> except for pagefaults to pull data in, which are obviously unavoidable

Umm, obviously that's what I mean. And with async IO instead of memory mapping, you could avoid that. Hence why I said memory mapping has disadvantages. Clearly the "nonsense" was invented at your end.

[hyc_symas]

Eh. You're still talking nonsense. If an app requests some data and it needs to be read in from disk, you have to wait. Async I/O or not, that app can't make any progress until its data arrives. Async I/O is only advantageous for writes.

[jules]

That's incorrect, even for reads the app can do something else at the same time while the disk read is being performed. That's what async I/O is all about.

[hyc_symas]

The app can do whatever else it wants to do that's completely unrelated to the data request. The part of the app that requested the data is stalled until the data arrives. If the data request is the only useful thing going on (e.g., a user clicked "search for Joe's phone number") then there's nothing else productive for the app to do and async I/O is irrelevant.

[jules]

Yes. That last bit is very rare, especially in server applications where you have multiple clients. In any case you might want to be a little more careful before calling something that you didn't understand nonsense.

[hyc_symas]

In server applications you have multiple threads too. Individual clients may stall but overall a large number of clients progress.

[jules]

Yes, I already pointed that out, so we're finally back to what I already originally said ;-)