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Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022

From Johnny Billquist <bqt@softjar.se>
Newsgroups alt.sys.pdp10, alt.folklore.computers
Subject Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022
Date 2022-03-08 00:06 +0100
Organization MGT Consulting
Message-ID <t06367$ep9$1@news.misty.com> (permalink)
References (6 earlier) <mdd1qzek05q.fsf@panix5.panix.com> <CcpVJ.46114$mF2.31622@fx11.iad> <mddee3d4db3.fsf@panix5.panix.com> <DKvVJ.164322$t2Bb.114365@fx98.iad> <c6wVJ.106047$aT3.10944@fx09.iad>

Cross-posted to 2 groups.

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On 2022-03-07 23:58, Scott Lurndal wrote:
> scott@slp53.sl.home (Scott Lurndal) writes:
>> It's changing between rings that is the primary issue as that often
>> includes a change in the memory context (e.g. x86 segment, active page
>> table) resulting in a performance hit.   E.g. UUO's/system calls.
> 
> What really killed it on the VAX was multiple ring changes for many
> operations (file operations executed in executive mode, and they
> called kernel mode facilities like $QIO/$QIOW).   On the other hand,
> user mode could make requests to DCL with a change mode to supervisor
> call.

What do you mean "killed it on the VAX"? Changing mode means trapping to 
the OS. Doing a system call means trapping to the OS. Is a change mode 
any more costly than any system call? No.

Are you claiming there is some extra performance penalty here?

You could argue that the changing of modes carried a performance 
benefit, since it meant you did not need to switch context to another 
process, and you did not need to flush TLBs and so on, since the memory 
mapping is unchanged. Changing modes effectively just changed what parts 
of memory was accessible, apart from kernel mode which allowed some 
instructions not allowed otherwise.
And that is also why implementing the whole thing on a processor with 
fewer modes isn't really a big deal. It's just a question of what your 
page table looks like. And that can obviously be changed whenever you 
trap into the OS anyway.

   Johnny

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Thread

TOPS-20 Boot Camp for VMS Users 05-Mar-2022 "Stephen M. Jones" <smj@ma.sdf.org> - 2022-03-02 21:32 +0000
  Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 scott@slp53.sl.home (Scott Lurndal) - 2022-03-03 14:30 +0000
    Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Ahem A Rivet's Shot <steveo@eircom.net> - 2022-03-03 16:38 +0000
      Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 scott@slp53.sl.home (Scott Lurndal) - 2022-03-03 17:13 +0000
        Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Rich Alderson <news@alderson.users.panix.com> - 2022-03-03 15:33 -0500
          Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 scott@slp53.sl.home (Scott Lurndal) - 2022-03-03 21:55 +0000
            Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Peter Flass <peter_flass@yahoo.com> - 2022-03-04 12:06 -0700
              Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Paul Rubin <no.email@nospam.invalid> - 2022-03-04 13:23 -0800
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Johnny Billquist <bqt@softjar.se> - 2022-03-06 17:29 +0100
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Peter Flass <peter_flass@yahoo.com> - 2022-03-06 11:34 -0700
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 scott@slp53.sl.home (Scott Lurndal) - 2022-03-06 19:40 +0000
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Charles Richmond <codescott@aquaporin4.com> - 2022-12-23 11:49 -0600
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 gah4 <gah4@u.washington.edu> - 2022-12-26 12:49 -0800
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Paul Rubin <no.email@nospam.invalid> - 2022-03-06 11:17 -0800
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Johnny Billquist <bqt@softjar.se> - 2022-03-07 17:53 +0100
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Vir Campestris <vir.campestris@invalid.invalid> - 2022-03-07 22:02 +0000
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Charles Richmond <codescott@aquaporin4.com> - 2022-12-23 11:55 -0600
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Peter Flass <peter_flass@yahoo.com> - 2022-12-23 12:27 -0700
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2022-03-07 03:11 +0000
              Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 gah4 <gah4@u.washington.edu> - 2022-03-08 22:46 -0800
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Johnny Billquist <bqt@softjar.se> - 2022-03-09 11:10 +0100
          Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Bob Eager <news0009@eager.cx> - 2022-03-04 00:46 +0000
            Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 "Stephen M. Jones" <smj@ma.sdf.org> - 2022-03-04 18:49 +0000
              Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 drb@ihatespam.msu.edu (Dennis Boone) - 2022-03-04 14:55 -0600
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 scott@slp53.sl.home (Scott Lurndal) - 2022-03-04 22:14 +0000
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Bob Eager <news0009@eager.cx> - 2022-03-04 22:17 +0000
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 David Lesher <wb8foz@panix.com> - 2022-03-06 04:35 +0000
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Ahem A Rivet's Shot <steveo@eircom.net> - 2022-03-06 05:40 +0000
            Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Rich Alderson <news@alderson.users.panix.com> - 2022-03-04 22:46 -0500
          Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Johnny Billquist <bqt@softjar.se> - 2022-03-06 17:21 +0100
            Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Peter Flass <peter_flass@yahoo.com> - 2022-03-06 11:34 -0700
              Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Johnny Billquist <bqt@softjar.se> - 2022-03-07 17:42 +0100
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 "P.Lj" <peter.ljungberg.sui@gmail.com> - 2022-03-18 13:36 -0700
            Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Rich Alderson <news@alderson.users.panix.com> - 2022-03-06 20:43 -0500
              Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Lars Brinkhoff <lars.spam@nocrew.org> - 2022-03-07 07:11 +0000
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Paul Rubin <no.email@nospam.invalid> - 2022-03-07 00:33 -0800
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Rich Alderson <news@alderson.users.panix.com> - 2022-03-07 17:03 -0500
              Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 scott@slp53.sl.home (Scott Lurndal) - 2022-03-07 15:07 +0000
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Johnny Billquist <bqt@softjar.se> - 2022-03-07 17:51 +0100
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 scott@slp53.sl.home (Scott Lurndal) - 2022-03-07 17:07 +0000
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Peter Flass <peter_flass@yahoo.com> - 2022-03-07 11:47 -0700
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 scott@slp53.sl.home (Scott Lurndal) - 2022-03-07 19:19 +0000
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Andreas Eder <a_eder_muc@web.de> - 2022-03-08 10:08 +0100
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Ahem A Rivet's Shot <steveo@eircom.net> - 2022-03-08 10:54 +0000
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Peter Flass <peter_flass@yahoo.com> - 2022-03-08 07:49 -0700
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Lars Brinkhoff <lars.spam@nocrew.org> - 2022-03-08 18:52 +0000
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Rich Alderson <news@alderson.users.panix.com> - 2022-03-08 17:34 -0500
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Alan Bawden <alan@csail.mit.edu> - 2022-03-09 00:46 -0500
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Lars Brinkhoff <lars.spam@nocrew.org> - 2022-03-09 06:48 +0000
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Charles Richmond <codescott@aquaporin4.com> - 2022-12-23 12:07 -0600
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Johnny Billquist <bqt@softjar.se> - 2022-03-09 11:11 +0100
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Andreas Eder <a_eder_muc@web.de> - 2022-03-09 20:10 +0100
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 "Stephen M. Jones" <smj@ma.sdf.org> - 2022-03-13 22:20 +0000
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Johnny Billquist <bqt@softjar.se> - 2022-03-16 19:11 +0100
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Rich Alderson <news@alderson.users.panix.com> - 2022-03-09 14:47 -0500
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Eric Swenson <eric@swenson.org> - 2022-03-11 10:25 -0800
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Sid Maxwell <srmaxwell3@gmail.com> - 2022-03-11 09:14 -0800
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 "P.Lj" <peter.ljungberg.sui@gmail.com> - 2022-03-18 13:41 -0700
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2022-03-08 19:47 +0000
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Bob Eager <news0009@eager.cx> - 2022-03-09 01:03 +0000
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Johnny Billquist <bqt@softjar.se> - 2022-03-08 16:34 +0100
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Lars Brinkhoff <lars.spam@nocrew.org> - 2022-03-08 18:59 +0000
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Johnny Billquist <bqt@softjar.se> - 2022-03-08 22:00 +0100
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Lars Brinkhoff <lars.spam@nocrew.org> - 2022-03-08 21:20 +0000
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Johnny Billquist <bqt@softjar.se> - 2022-03-09 11:13 +0100
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Charles Richmond <codescott@aquaporin4.com> - 2022-12-23 12:13 -0600
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 cross@spitfire.i.gajendra.net (Dan Cross) - 2022-03-11 13:56 +0000
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Johnny Billquist <bqt@softjar.se> - 2022-03-12 01:12 +0100
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Phil Budne <phil.budne@gmail.com> - 2022-03-12 11:40 -0800
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Phil Budne <phil.budne@gmail.com> - 2022-03-12 11:43 -0800
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 cross@spitfire.i.gajendra.net (Dan Cross) - 2022-03-12 22:01 +0000
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Johnny Billquist <bqt@softjar.se> - 2022-03-07 20:18 +0100
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 scott@slp53.sl.home (Scott Lurndal) - 2022-03-07 19:37 +0000
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Dan Espen <dan1espen@gmail.com> - 2022-03-07 14:53 -0500
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 scott@slp53.sl.home (Scott Lurndal) - 2022-03-07 20:43 +0000
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Ahem A Rivet's Shot <steveo@eircom.net> - 2022-03-07 19:52 +0000
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Rich Alderson <news@alderson.users.panix.com> - 2022-03-07 17:18 -0500
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 scott@slp53.sl.home (Scott Lurndal) - 2022-03-07 22:33 +0000
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 scott@slp53.sl.home (Scott Lurndal) - 2022-03-07 22:58 +0000
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Johnny Billquist <bqt@softjar.se> - 2022-03-08 00:06 +0100
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Peter Flass <peter_flass@yahoo.com> - 2022-03-08 07:49 -0700
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 scott@slp53.sl.home (Scott Lurndal) - 2022-03-08 15:22 +0000
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Peter Flass <peter_flass@yahoo.com> - 2022-03-08 11:17 -0700
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Vir Campestris <vir.campestris@invalid.invalid> - 2022-03-08 21:09 +0000
                Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 scott@slp53.sl.home (Scott Lurndal) - 2022-03-08 21:33 +0000
              Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Johnny Billquist <bqt@softjar.se> - 2022-03-07 20:24 +0100
      Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Rich Alderson <news@alderson.users.panix.com> - 2022-03-03 15:24 -0500
        Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Ahem A Rivet's Shot <steveo@eircom.net> - 2022-03-03 21:06 +0000
          Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Rich Alderson <news@alderson.users.panix.com> - 2022-03-04 22:47 -0500
    Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Peter Flass <peter_flass@yahoo.com> - 2022-03-04 12:06 -0700
    Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 D.J. <chucktheouch@gmail.com> - 2022-03-07 10:48 -0600
      Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 scott@slp53.sl.home (Scott Lurndal) - 2022-03-07 17:03 +0000
        Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 D.J. <chucktheouch@gmail.com> - 2022-03-07 19:52 -0600
          Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Fred Smith <fred@thejanitor.corp> - 2022-03-08 04:13 +0000
            Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 Johnny Billquist <bqt@softjar.se> - 2022-03-08 16:32 +0100
      Re: TOPS-20 Boot Camp for VMS Users 05-Mar-2022 gah4 <gah4@u.washington.edu> - 2022-03-08 23:02 -0800

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