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Re: Performance of xchg reg,reg

From Michael S <already5chosen@yahoo.com>
Newsgroups comp.arch
Subject Re: Performance of xchg reg,reg
Date 2026-10-22 22:11 +0300
Organization A noiseless patient Spider
Message-ID <20261022221132.000070d5@yahoo.com> (permalink)
References (6 earlier) <2026Oct18.170823@mips.complang.tuwien.ac.at> <20261018184318.00000bee@yahoo.com> <2026Oct18.185726@mips.complang.tuwien.ac.at> <jwv8q3uqrxf.fsf-monnier+comp.arch@gnu.org> <2026Oct22.125404@mips.complang.tuwien.ac.at>

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On Thu, 22 Oct 2026 10:54:04 GMT
anton@mips.complang.tuwien.ac.at (Anton Ertl) wrote:

> Stefan Monnier <monnier@iro.umontreal.ca> writes:
> >Anton Ertl [2026-10-18 16:57:26] wrote:  
> >> And actually all the stuff about XCHG with memory operands does not
> >> contradict this sentence.  It could be understood as meaning that
> >> while all the other aspects of locking don't apply to "XCHG reg,
> >> reg", the assertion of the LOCK# signal still has to occur, and
> >> that's why Intel processors implement a slow XCHG reg, reg.  
> >
> >How could code witness the difference?  
> 
> Depends on the hardware.  If there is some device connected t the
> LOCK# signal (e.g., another CPU), and that behaves differently when
> the signal is asserted, the code can measure that.
> 
> - anton

My undersanding is that in server x86 CPU physical LOCK# signal does not
exist for more than decade. Probably much longer in desktop and laptop
devices.

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Performance of xchg reg,reg anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-10-13 08:43 +0000
  Re: Performance of xchg reg,reg Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-10-14 00:23 +0000
    Re: Performance of xchg reg,reg anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-10-14 07:00 +0000
      Re: Performance of xchg reg,reg MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-10-14 22:35 +0000
        Re: Performance of xchg reg,reg Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-10-14 23:07 +0000
        Re: Performance of xchg reg,reg anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-10-15 06:05 +0000
          Re: Performance of xchg reg,reg anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-10-15 07:06 +0000
            Re: Performance of xchg reg,reg EricP <ThatWouldBeTelling@thevillage.com> - 2026-10-16 09:47 -0400
              Re: Performance of xchg reg,reg anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-10-16 16:04 +0000
              Re: Performance of xchg reg,reg Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-10-17 05:46 +0000
  Re: Performance of xchg reg,reg Michael S <already5chosen@yahoo.com> - 2026-10-14 22:29 +0300
  Re: Performance of xchg reg,reg "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-10-15 14:21 -0700
    Re: Performance of xchg reg,reg Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-10-15 21:42 +0000
      Re: Performance of xchg reg,reg Terje Mathisen <terje.mathisen@tmsw.no> - 2026-10-16 14:45 +0200
    Re: Performance of xchg reg,reg anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-10-16 05:50 +0000
      Re: Performance of xchg reg,reg Michael S <already5chosen@yahoo.com> - 2026-10-16 11:34 +0300
        Re: Performance of xchg reg,reg cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-16 18:23 +0000
          Re: Performance of xchg reg,reg scott@slp53.sl.home (Scott Lurndal) - 2026-10-16 20:48 +0000
            Re: Performance of xchg reg,reg "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-10-16 14:28 -0700
            Re: Performance of xchg reg,reg Thomas Koenig <tkoenig@netcologne.de> - 2026-10-17 09:48 +0000
          Re: Performance of xchg reg,reg cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-17 02:50 +0000
            Re: Performance of xchg reg,reg MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-10-17 17:11 +0000
              Re: Performance of xchg reg,reg cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-17 17:31 +0000
                Re: Performance of xchg reg,reg MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-10-17 19:39 +0000
                Re: Performance of xchg reg,reg Michael S <already5chosen@yahoo.com> - 2026-10-17 23:20 +0300
                Re: Documentation (was Re: Performance of xchg reg,reg) Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-10-17 20:54 +0000
                Re: Documentation (was Re: Performance of xchg reg,reg) George Neuner <gneuner2@comcast.net> - 2026-10-18 09:45 -0400
                Algol 68 (was: Documentation (was Re: Performance of xchg reg,reg)) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-10-18 14:08 +0000
                Re: Algol 68 (was: Documentation (was Re: Performance of xchg reg,reg)) quadibloc@invalid.com (John Savard) - 2026-10-19 00:09 +0000
                Re: Algol 68 (was Re: Documentation) Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-10-19 01:46 +0000
                Re: Algol 68 (was Re: Documentation) quadibloc@invalid.com (John Savard) - 2026-10-21 14:15 +0000
                Re: Algol 68 (was Re: Documentation) Niklas Holsti <niklas.holsti@tidorum.invalid> - 2026-10-21 18:34 +0300
                Re: Algol 68 (was Re: Documentation) quadibloc@invalid.com (John Savard) - 2026-10-21 19:38 +0000
                Re: Algol 68 (was Re: Documentation) aph@littlepinkcloud.invalid - 2026-10-22 09:51 +0000
                Re: Algol 68 (was Re: Documentation) Stephen Fuld <sfuld@alumni.cmu.edu.invalid> - 2026-10-22 14:15 -0700
                Re: Algol 68 (was Re: Documentation) scott@slp53.sl.home (Scott Lurndal) - 2026-10-23 14:08 +0000
                Re: PL/I, was Algol 68 (was: Documentation (was Re: Performance of xchg reg,reg)) John Levine <johnl@taugh.com> - 2026-10-19 03:24 +0000
                Re: PL/I, was Algol 68 (was: Documentation (was Re: Performance of xchg reg,reg)) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-10-19 05:34 +0000
                Re: Algol 68 Stefan Monnier <monnier@iro.umontreal.ca> - 2026-10-18 23:34 -0400
                Re: Documentation (was Re: Performance of xchg reg,reg) quadibloc@invalid.com (John Savard) - 2026-10-19 00:18 +0000
                Re: Documentation (was Re: Performance of xchg reg,reg) cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-19 01:52 +0000
                Re: Documentation (was Re: Performance of xchg reg,reg) George Neuner <gneuner2@comcast.net> - 2026-10-19 14:50 -0400
                Re: Documentation (was Re: Performance of xchg reg,reg) cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-20 02:05 +0000
                Re: Algol 68 (was Re: Documentation) Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-10-19 01:54 +0000
                Re: Documentation (was Re: Performance of xchg reg,reg) Thomas Koenig <tkoenig@netcologne.de> - 2026-10-19 07:44 +0000
                Re: Documentation (was Re: Performance of xchg reg,reg) Stefan Monnier <monnier@iro.umontreal.ca> - 2026-10-19 12:24 -0400
                Re: Documentation (was Re: Performance of xchg reg,reg) MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-10-18 17:48 +0000
                Re: Performance of xchg reg,reg George Neuner <gneuner2@comcast.net> - 2026-10-18 08:59 -0400
                Re: Performance of xchg reg,reg anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-10-18 15:08 +0000
                Re: Performance of xchg reg,reg Michael S <already5chosen@yahoo.com> - 2026-10-18 18:43 +0300
                Re: Performance of xchg reg,reg anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-10-18 16:57 +0000
                Re: Performance of xchg reg,reg Michael S <already5chosen@yahoo.com> - 2026-10-18 20:47 +0300
                Re: Performance of xchg reg,reg cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-18 18:07 +0000
                Re: Performance of xchg reg,reg anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-10-18 21:04 +0000
                Re: Performance of xchg reg,reg Stefan Monnier <monnier@iro.umontreal.ca> - 2026-10-18 23:43 -0400
                Re: Performance of xchg reg,reg Stephen Fuld <sfuld@alumni.cmu.edu.invalid> - 2026-10-19 06:57 -0700
                Re: Performance of xchg reg,reg "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-10-19 14:27 -0700
                Re: Performance of xchg reg,reg Stefan Monnier <monnier@iro.umontreal.ca> - 2026-10-20 10:00 -0400
                Re: Performance of xchg reg,reg cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-20 02:00 +0000
                Re: Performance of xchg reg,reg scott@slp53.sl.home (Scott Lurndal) - 2026-10-20 14:09 +0000
                Re: Performance of xchg reg,reg "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-10-20 16:44 -0700
                Re: Performance of xchg reg,reg Stefan Monnier <monnier@iro.umontreal.ca> - 2026-10-20 10:05 -0400
                Re: Performance of xchg reg,reg cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-20 19:56 +0000
                Re: Performance of xchg reg,reg anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-10-22 10:54 +0000
                Re: Performance of xchg reg,reg Michael S <already5chosen@yahoo.com> - 2026-10-22 22:11 +0300
                Re: Performance of xchg reg,reg cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-18 17:40 +0000
                Re: Performance of xchg reg,reg Michael S <already5chosen@yahoo.com> - 2026-10-18 20:54 +0300
                Re: Performance of xchg reg,reg cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-18 18:25 +0000
                Re: Performance of xchg reg,reg MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-10-18 18:01 +0000
                Re: Performance of xchg reg,reg cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-18 17:59 +0000
                Re: Performance of xchg reg,reg cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-18 17:09 +0000
                Re: Performance of xchg reg,reg EricP <ThatWouldBeTelling@thevillage.com> - 2026-10-18 12:31 -0400
                Re: Performance of xchg reg,reg cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-18 17:47 +0000
            Re: Performance of xchg reg,reg "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-10-18 12:27 -0700
              Re: Performance of xchg reg,reg EricP <ThatWouldBeTelling@thevillage.com> - 2026-10-19 09:38 -0400
                Re: Performance of xchg reg,reg "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-10-19 14:08 -0700
                Re: Performance of xchg reg,reg Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-10-19 21:21 +0000
                Re: Performance of xchg reg,reg "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-10-19 14:26 -0700
                Re: Performance of xchg reg,reg Joseph Seigh <jseigh_es00@xemaps.com> - 2026-10-19 19:17 -0400
                Re: Performance of xchg reg,reg "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-10-19 22:41 -0700
                Re: Performance of xchg reg,reg MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-10-20 16:45 +0000

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