Xref: utzoo comp.lang.misc:5430 comp.unix.internals:5 Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!usc!jarthur!uunet!dg!dg-rtp.dg.com!lewine From: lewine@dg-rtp.dg.com (Donald Lewine) Newsgroups: comp.lang.misc,comp.unix.internals Subject: Re: UNIX semantics do permit full support for asynchronous I/O Message-ID: <861@dg.dg.com> Date: 29 Aug 90 13:12:57 GMT References: <126800008@.Prime.COM> <60345@lanl.gov> <1990Aug21.223350.7595@esegue.segue.boston.ma.us> <11576:Aug2503:18:3790@kramden.acf.nyu.edu> <27619@nuchat.UUCP> Sender: root@dg.dg.com Reply-To: uunet!dg!lewine Distribution: usa Organization: Data General Corporation Lines: 35 In article <27619@nuchat.UUCP>, steve@nuchat.UUCP (Steve Nuchia) writes: |> (For completeness I will note that to use this scheme intelligently |> you must be able to discover the relevant properties of the memory |> management implementation. This is nothing new for high performance |> programs in a paged environment, but unless its been added recently |> there isn't a standard way to do it. Whether this is properly a |> language or a system interface issue is best left to another debate.) |> -- 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. If you blindly map the page(s) containing "buf" out of the users address space you will map out other variables that the user may want. It is not possible for the compiler to know that buf must be on a page by itself. How could you implement your scheme? 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! I don't think that your idea works at all. For a scheme that does almost exactly this, but with the cooperation of the user program, look at PMAP under DEC's TOPS-20 operating system or ?SPAGE under DG's AOS/VS. -------------------------------------------------------------------- Donald A. Lewine (508) 870-9008 Data General Corporation (508) 366-0750 FAX 4400 Computer Drive. MS D112A Westboro, MA 01580 U.S.A. uucp: uunet!dg!lewine Internet: lewine@cheshirecat.webo.dg.com