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| From | Stefan Monnier <monnier@iro.umontreal.ca> |
|---|---|
| Newsgroups | comp.arch |
| Subject | Re: unaligned load/store |
| Date | 2024-12-26 13:38 -0500 |
| Organization | A noiseless patient Spider |
| Message-ID | <jwvh66qtimu.fsf-monnier+comp.arch@gnu.org> (permalink) |
| References | (5 earlier) <jwvmshc49i0.fsf-monnier+comp.arch@gnu.org> <9534a1cd1364f2127a1951cc85002f29@www.novabbs.org> <lsp0tqFs7aoU1@mid.individual.net> <cadda24092db49d26e62096c589fbf9c@www.novabbs.org> <vk9us6$pm19$1@dont-email.me> |
>> Aligned data is always best, Misaligned data comes at very low cost.
>> SW overhead = 0
> Thinking about this for a bit... for a clean-sheet architecture
> like My66000, could there actually be an advantage to do
> struct layout like the VAX did, with everything aligned on byte
> boundaries?
I highly doubt it. Making unaligned accesses work efficiently is great,
but that's no reason to abuse them:
- Going back to Mitch's description, in case B.1 the misalignment is
truly "free", but for B.2, B.3, and B.4 the misalignment does come at
a cost, not necessarily visible in terms of cycles but at least in
terms of cache bandwidth, which can have an impact on overall speed
and energy use.
Of course, properly aligning your data will also come with costs,
but "packed structs" don't come totally free.
- AFAIK most efforts to support concurrency take it for granted that
atomic accesses are supported only when properly aligned.
I expect it's at least as easy (and more portable) to reorder fields by
order of (expected) size to avoid excessive padding in aligned data,
than it is to add manual padding/alignment to avoid the cost of
misalignment in "packed structs".
Stefan
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What is an N-bit machine? jgd@cix.co.uk (John Dallman) - 2024-11-28 15:31 +0000
Re: What is an N-bit machine? scott@slp53.sl.home (Scott Lurndal) - 2024-11-28 16:33 +0000
Re: What is an N-bit machine? Michael S <already5chosen@yahoo.com> - 2024-11-28 18:55 +0200
Re: What is an N-bit machine? John Levine <johnl@taugh.com> - 2024-11-30 02:37 +0000
Re: What is an N-bit machine? Stephen Fuld <sfuld@alumni.cmu.edu.invalid> - 2024-11-29 22:30 -0800
Re: What is an N-bit machine? John Levine <johnl@taugh.com> - 2024-11-30 19:40 +0000
Re: What is an N-bit machine? Michael S <already5chosen@yahoo.com> - 2024-11-30 22:38 +0200
Re: What is an N-bit machine? "Paul A. Clayton" <paaronclayton@gmail.com> - 2024-12-01 11:23 -0500
Re: What is an N-bit machine? scott@slp53.sl.home (Scott Lurndal) - 2024-12-01 19:52 +0000
Re: What is an N-bit machine? mitchalsup@aol.com (MitchAlsup1) - 2024-11-30 22:39 +0000
Re: What is an N-bit machine? Thomas Koenig <tkoenig@netcologne.de> - 2024-12-01 08:19 +0000
Re: What is an N-bit machine? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2024-12-01 08:35 +0000
Re: What is an N-bit machine? Terje Mathisen <terje.mathisen@tmsw.no> - 2024-12-02 09:48 +0100
Re: What is an N-bit machine? "Brian G. Lucas" <bagel99@gmail.com> - 2024-12-02 19:56 -0500
Re: What is an N-bit machine? Stephen Fuld <sfuld@alumni.cmu.edu.invalid> - 2024-12-03 00:01 -0800
Re: What is an N-bit machine? antispam@fricas.org (Waldek Hebisch) - 2024-12-15 18:20 +0000
Keeping other stuff with addresses (was: What is an N-bit machine?) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2024-11-30 06:28 +0000
Re: Keeping other stuff with addresses (was: What is an N-bit machine?) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2024-11-30 11:35 +0000
Re: Keeping other stuff with addresses (was: What is an N-bit machine?) Thomas Koenig <tkoenig@netcologne.de> - 2024-11-30 11:58 +0000
Re: Keeping other stuff with addresses (was: What is an N-bit machine?) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2024-11-30 16:57 +0000
Re: Keeping other stuff with addresses (was: What is an N-bit machine?) Michael S <already5chosen@yahoo.com> - 2024-11-30 19:32 +0200
Re: Keeping other stuff with addresses (was: What is an N-bit machine?) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2024-11-30 18:08 +0000
Re: Keeping other stuff with addresses (was: What is an N-bit machine?) Michael S <already5chosen@yahoo.com> - 2024-11-30 20:28 +0200
Re: Keeping other stuff with addresses (was: What is an N-bit machine?) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2024-12-01 09:28 +0000
Re: Keeping other stuff with addresses (was: What is an N-bit machine?) Thomas Koenig <tkoenig@netcologne.de> - 2024-12-01 14:03 +0000
Re: Keeping other stuff with addresses David Schultz <david.schultz@earthlink.net> - 2024-12-01 08:15 -0600
Re: Keeping other stuff with addresses Thomas Koenig <tkoenig@netcologne.de> - 2024-12-01 14:40 +0000
Re: Keeping other stuff with addresses mitchalsup@aol.com (MitchAlsup1) - 2024-12-04 02:19 +0000
Re: Keeping other stuff with addresses John Levine <johnl@taugh.com> - 2024-12-04 03:25 +0000
Re: Keeping other stuff with addresses (was: What is an N-bit machine?) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-12-01 07:32 -0800
Re: Keeping other stuff with addresses (was: What is an N-bit machine?) Thomas Koenig <tkoenig@netcologne.de> - 2024-12-01 17:53 +0000
Re: Keeping other stuff with addresses (was: What is an N-bit machine?) Michael S <already5chosen@yahoo.com> - 2024-12-01 20:05 +0200
Re: Keeping other stuff with addresses EricP <ThatWouldBeTelling@thevillage.com> - 2024-12-01 18:16 -0500
Re: Keeping other stuff with addresses (was: What is an N-bit machine?) Brett <ggtgp@yahoo.com> - 2024-12-01 20:02 +0000
Re: Keeping other stuff with addresses (was: What is an N-bit machine?) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-12-31 08:54 -0800
Re: Keeping other stuff with addresses (was: What is an N-bit machine?) Thomas Koenig <tkoenig@netcologne.de> - 2025-01-01 15:28 +0000
Re: Keeping other stuff with addresses (was: What is an N-bit machine?) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-01-01 17:39 -0800
Re: Keeping other stuff with addresses (was: What is an N-bit machine?) Thomas Koenig <tkoenig@netcologne.de> - 2025-01-02 09:59 +0000
Re: Keeping other stuff with addresses (was: What is an N-bit machine?) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-01-08 10:00 -0800
Re: Keeping other stuff with addresses (was: What is an N-bit machine?) Thomas Koenig <tkoenig@netcologne.de> - 2025-01-08 19:18 +0000
Re: Keeping other stuff with addresses (was: What is an N-bit machine?) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-01-27 17:05 -0800
Re: Keeping other stuff with addresses David Brown <david.brown@hesbynett.no> - 2025-01-28 08:30 +0100
Re: Keeping other stuff with addresses Thomas Koenig <tkoenig@netcologne.de> - 2025-02-02 08:37 +0000
Re: Keeping other stuff with addresses Terje Mathisen <terje.mathisen@tmsw.no> - 2024-12-02 17:10 +0100
Re: Keeping other stuff with addresses Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-12-31 08:46 -0800
Re: Keeping other stuff with addresses (was: What is an N-bit machine?) John Levine <johnl@taugh.com> - 2024-11-30 19:12 +0000
What is an N-bit machine? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2024-12-01 08:41 +0000
Re: What is an N-bit machine? scott@slp53.sl.home (Scott Lurndal) - 2024-12-01 15:52 +0000
Re: What is an N-bit machine? antispam@fricas.org (Waldek Hebisch) - 2024-12-16 22:39 +0000
Re: Keeping other stuff with addresses (was: What is an N-bit machine?) Thomas Koenig <tkoenig@netcologne.de> - 2024-11-30 22:06 +0000
Re: Keeping other stuff with addresses (was: What is an N-bit machine?) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2024-12-01 08:38 +0000
Re: Keeping other stuff with addresses (was: What is an N-bit machine?) scott@slp53.sl.home (Scott Lurndal) - 2024-11-30 17:57 +0000
Re: Keeping other stuff with addresses (was: What is an N-bit machine?) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2024-12-01 09:38 +0000
Re: Keeping other stuff with addresses "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-12-01 15:22 -0800
Re: Keeping other stuff with addresses mitchalsup@aol.com (MitchAlsup1) - 2024-12-02 01:26 +0000
Re: Keeping other stuff with addresses "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-12-01 20:12 -0800
Re: Keeping other stuff with addresses "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-12-02 16:54 -0800
Re: Keeping other stuff with addresses Stefan Monnier <monnier@iro.umontreal.ca> - 2024-12-03 11:51 -0500
Re: Keeping other stuff with addresses John Levine <johnl@taugh.com> - 2024-12-03 18:19 +0000
Re: Keeping other stuff with addresses Stefan Monnier <monnier@iro.umontreal.ca> - 2024-12-03 13:46 -0500
Re: Keeping other stuff with addresses John Levine <johnl@taugh.com> - 2024-12-03 23:33 +0000
Re: Keeping other stuff with addresses Stefan Monnier <monnier@iro.umontreal.ca> - 2024-12-03 18:52 -0500
Re: Keeping other stuff with addresses mitchalsup@aol.com (MitchAlsup1) - 2024-12-04 02:36 +0000
Re: Keeping other stuff with addresses Thomas Koenig <tkoenig@netcologne.de> - 2024-12-04 06:29 +0000
Re: Keeping other stuff with addresses Stefan Monnier <monnier@iro.umontreal.ca> - 2024-12-04 10:32 -0500
Re: Keeping other stuff with addresses mitchalsup@aol.com (MitchAlsup1) - 2024-12-04 19:47 +0000
Re: Keeping other stuff with addresses Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-12-04 15:47 -0800
Re: Keeping other stuff with addresses scott@slp53.sl.home (Scott Lurndal) - 2024-12-04 16:31 +0000
Re: bytes, Keeping other stuff with addresses John Levine <johnl@taugh.com> - 2024-12-05 00:39 +0000
unaligned load/store (was: Re: Keeping other stuff with addresses) Jonathan Thornburg <jonathan@gold.bkis-orchard.net> - 2024-12-21 23:22 +0000
Re: unaligned load/store mitchalsup@aol.com (MitchAlsup1) - 2024-12-22 01:27 +0000
Re: unaligned load/store Thomas Koenig <tkoenig@netcologne.de> - 2024-12-22 10:01 +0000
Re: unaligned load/store anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2024-12-22 11:06 +0000
Re: unaligned load/store jgd@cix.co.uk (John Dallman) - 2024-12-22 11:42 +0000
Re: unaligned load/store "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-12-22 19:41 -0800
Re: unaligned load/store Thomas Koenig <tkoenig@netcologne.de> - 2024-12-22 21:04 +0000
Re: unaligned load/store mitchalsup@aol.com (MitchAlsup1) - 2024-12-22 23:32 +0000
Re: unaligned load/store Stefan Monnier <monnier@iro.umontreal.ca> - 2024-12-26 13:38 -0500
Re: unaligned load/store George Neuner <gneuner2@comcast.net> - 2024-12-26 16:31 -0500
Re: unaligned load/store mitchalsup@aol.com (MitchAlsup1) - 2024-12-26 21:59 +0000
Re: unaligned load/store "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-12-26 14:05 -0800
Re: unaligned load/store (was: Re: Keeping other stuff with addresses) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2024-12-22 10:33 +0000
Re: bits and bytes, Keeping other stuff with addresses John Levine <johnl@taugh.com> - 2024-12-04 03:39 +0000
Re: bits and bytes, Keeping other stuff with addresses Stefan Monnier <monnier@iro.umontreal.ca> - 2024-12-04 10:36 -0500
Re: Keeping other stuff with addresses mitchalsup@aol.com (MitchAlsup1) - 2024-12-03 19:22 +0000
Re: Keeping other stuff with addresses "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-12-03 17:03 -0800
Re: Keeping other stuff with addresses "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-12-03 16:56 -0800
Re: Keeping other stuff with addresses Stefan Monnier <monnier@iro.umontreal.ca> - 2024-12-04 10:37 -0500
Re: Keeping other stuff with addresses Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-12-03 17:43 -0800
Re: Keeping other stuff with addresses mitchalsup@aol.com (MitchAlsup1) - 2024-12-04 02:42 +0000
Re: What is an N-bit machine? Thomas Koenig <tkoenig@netcologne.de> - 2024-11-28 17:56 +0000
Re: What is an N-bit machine? mitchalsup@aol.com (MitchAlsup1) - 2024-11-28 19:02 +0000
Re: What is an N-bit machine? Brett <ggtgp@yahoo.com> - 2024-11-28 19:39 +0000
Re: What is an N-bit machine? Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-11-28 21:42 +0000
Re: What is an N-bit machine? jgd@cix.co.uk (John Dallman) - 2024-11-28 22:08 +0000
Re: What is an N-bit machine? Lynn Wheeler <lynn@garlic.com> - 2024-11-28 12:44 -1000
Re: What is an N-bit machine? jgd@cix.co.uk (John Dallman) - 2024-11-28 22:58 +0000
IBM and Amdahl history (Re: What is an N-bit machine?) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2024-11-29 07:22 +0000
Re: IBM and Amdahl history (Re: What is an N-bit machine?) Lynn Wheeler <lynn@garlic.com> - 2024-11-29 08:24 -1000
Re: IBM and Amdahl history (Re: What is an N-bit machine?) scott@slp53.sl.home (Scott Lurndal) - 2024-11-29 18:29 +0000
Re: IBM and Amdahl history (Re: What is an N-bit machine?) Lynn Wheeler <lynn@garlic.com> - 2024-11-29 11:51 -1000
Re: IBM and Amdahl history (Re: What is an N-bit machine?) Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-11-29 21:51 +0000
Re: IBM and Amdahl history (Re: What is an N-bit machine?) scott@slp53.sl.home (Scott Lurndal) - 2024-11-30 17:45 +0000
Re: IBM and Amdahl history (Re: What is an N-bit machine?) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2024-11-30 18:19 +0000
Re: IBM and Amdahl history (Re: What is an N-bit machine?) jgd@cix.co.uk (John Dallman) - 2024-11-30 22:19 +0000
Re: IBM and Amdahl history (Re: What is an N-bit machine?) Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-11-30 23:21 +0000
Re: What is an N-bit machine? Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-11-29 02:17 +0000
Re: What is an N-bit machine? Brett <ggtgp@yahoo.com> - 2024-11-30 01:29 +0000
Re: market power, What is an N-bit machine? John Levine <johnl@taugh.com> - 2024-11-30 02:42 +0000
Re: What is an N-bit machine? Lynn Wheeler <lynn@garlic.com> - 2024-11-29 17:42 -1000
Re: What is an N-bit machine? mitchalsup@aol.com (MitchAlsup1) - 2024-11-28 19:01 +0000
Re: What is an N-bit machine? Lynn Wheeler <lynn@garlic.com> - 2024-11-28 11:45 -1000
Re: What is an N-bit machine? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2024-11-29 08:03 +0000
Re: What is an N-bit machine? Thomas Koenig <tkoenig@netcologne.de> - 2024-11-29 19:17 +0000
Re: What is an N-bit machine? Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-12-22 21:37 +0000
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