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Article #625018Re: The history of the MONITOR tops-10)
From: John Levine
Date: Sun, 15 Jul 2018 12:57
Date: Sun, 15 Jul 2018 12:57
27 lines
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2696 bytes
In article <pieq2s$ctl$1...@dont-email.me>, Rob Warnock <rp...@rpw3.org> wrote: >Actually, TOPS-10 user-space buffered I/O was closer to Linux/Unix's >DIRECT_IO mode than to mmap(), except it was naturally multi-buffered. > >That is, you had a *ring* of user-space buffers, with ownership flags >so both the kernel and the user program could see who was working >on a given buffer. This quite naturally allowed kernel I/O and the >user program to work asynchronously, as long as neither side caught >up to the portion of the ring owned by the other side. [And if that >happens, the faster side simply stopped until there was a free (or full) >buffer available for it.] OS/360 QSAM worked pretty much the same way, device I/O in and out of a ring of user space buffers. This shows up in the PL/I LOCATE mode for file I/O, where it gives you a pointer to the record it just read or that you are about to write. I suppose it still does in z/OS although these days it's likely all faked with copies from memory mapped buffers since modern disks don't have variable sized records like CKD disks did. R's, John -- Regards, John Levine, jo...@iecc.com, Primary Perpetrator of "The Internet for Dummies", Please consider the environment before reading this e-mail. https://jl.ly
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X-Received: by 2002:a5e:8e08:: with SMTP id a8-v6mr5734072ion.134.1531659449484; Sun, 15 Jul 2018 05:57:29 -0700 (PDT) X-BeenThere: alt.folklore.computers@googlegroups.com Received: by 2002:a24:c9c6:: with SMTP id h189-v6ls55219itg.7.canary-gmail; Sun, 15 Jul 2018 05:57:28 -0700 (PDT) X-Received: by 2002:a24:5d08:: with SMTP id w8-v6mr5518222ita.22.1531659448707; Sun, 15 Jul 2018 05:57:28 -0700 (PDT) MIME-Version: 1.0 Path: mbox-mo1.pugleaf.net!l67-v6ni4701itl.0!nntp.google.com!border1.nntp.dca1.giganews.com!nntp.giganews.com!news.iecc.com!.POSTED.news.iecc.com!not-for-mail From: John Levine <jo...@taugh.com> Newsgroups: alt.sys.pdp10,alt.folklore.computers Subject: Re: The history of the MONITOR tops-10) Date: Sun, 15 Jul 2018 12:57:28 -0000 (UTC) Organization: Taughannock Networks Message-ID: <pifgbo$2b9c$1@gal.iecc.com> References: <pib5q8$f7v$1@sdf.lonestar.org> <pid2ak$15mo$1@gal.iecc.com> <pidigf$p59$1@Iltempo.Update.UU.SE> <pieq2s$ctl$1@dont-email.me> Injection-Date: Sun, 15 Jul 2018 12:57:28 -0000 (UTC) Injection-Info: gal.iecc.com; posting-host="news.iecc.com:2001:470:1f07:1126:0:676f:7373:6970"; logging-data="77100"; mail-complaints-to="ab...@iecc.com" Cleverness: some X-Newsreader: trn 4.0-test77 (Sep 1, 2010) Originator: jo...@iecc.com (John Levine) Bytes: 2187 Lines: 26 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit