UNIX semantics do permit full support for asynchronous I/O

[Peter da Silva]

In article <861 at dg.dg.com> uunet!dg!lewine writes:
> That last remark defeats your entire suggestion.  If I have to
> "discover the relevant properties of the memory management 
> implementation", all dusty decks will fail.  

You only have to do this if you want to get some additional
performance. It should still work regardless.

> Also the read() and write() functions return the number of characters
> read or written.  How do you know this before the read() or write()
> completes?  Do you assume that all disks are error free and never
> fail?  That is a poor assumption!

Well, it's an assumption made for write() anyway. For read() you can just
treat it like any disk error on any other faulted-in page and blow off the
process. Disk errors are a very rare occurrence, and almost always require
human intervention anyway. Any other return value for read is known
ahead of time.
-- 
Peter da Silva.   `-_-'
+1 713 274 5180.   'U`
peter at ferranti.com