Sujet : Re: Address space limits
De : chris.m.thomasson.1 (at) *nospam* gmail.com (Chris M. Thomasson)
Groupes : comp.archDate : 07. May 2024, 03:30:57
Autres entêtes
Organisation : A noiseless patient Spider
Message-ID : <v1c08g$2snlg$1@dont-email.me>
References : 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
User-Agent : Mozilla Thunderbird
On 5/5/2024 11:13 PM, Terje Mathisen wrote:
MitchAlsup1 wrote:
Chris M. Thomasson wrote:
>
On 5/5/2024 3:25 PM, MitchAlsup1 wrote:
Chris M. Thomasson wrote:
>
On 5/4/2024 5:12 PM, MitchAlsup1 wrote:
Chris M. Thomasson wrote:
>
On 5/4/2024 3:18 AM, Thomas Koenig wrote:
Lawrence D'Oliveiro <ldo@nz.invalid> schrieb:
>
Intel pushed this thing called the “x32†ABI into the Linux kernel
(and
possibly some other places) some years ago. This was using the AMD64
instruction set, but with only 32-bit pointers. This way, you got the
benefit of the extra registers, without the overhead of the longer
addresses.
>
That was Donald Knuth's idea.
>
Storing meta data in actual pointers, aka aligned on a larger boundary, is critical to many advanced lock/wait free algorithms as well. I remember storing an actual reference count in pointers before for a special type of counting.
>
Even if one has multi-location ATOMICs ?? (as a single event ??)
>
This was a technique for storing data in a pointer. For instance, strong atomic reference counting we need to update a pointer _and_ a reference together atomically. This can easily be done with DWCAS, or double width compare and swap. So, on a 32 bit system we need 64 bit cas, for a 64 bit system we need 128 bit cas. However, sometimes we can pack the reference count in the pointer value itself if its aligned on a big enough boundary. Then we can update the pointer and the reference count using normal word based atomic RMW's.
>
I understand why you had to pack the pointer and a chunk of data into a
single container.
>
What I don't understand is if you had easy access to multi-container ATOMICs
the packing would be unnecessary--would it not ?? That is in one ATOMIC event
you could update the pointer and the chunk of data independently and not NEED
to store them in a single container.
>
Well, actually, a pessimistic word based fetch-and-add (LOCK XADD) is enough to increment the counter and load a pointer atomically all in one shot, loopless. Why would I need to use multi atomics with a possible loop to do that?
>
Postulate that you have a 64-bit pointer and a 8-bit chunk 72-total bits.
Further postulate that you need to update both in a single non-blocking ATOMIC event. ...
"Any programming problem can be solved with an additional layer of indirection", so in this case you create a handle to that 72-bit item, and require all access to go via the handle?
The addendum to the rule above is of course ", except the problem of too many layers of indirections". :-)
I remember look at one of your atomic queues that only used LOCK XADD on x86. Why would you use CAS for that? I don't know. I see no need for multi-atomics for any of it....
Date | Sujet | # | | Auteur |
1 May 24 | Byte Addressability And Beyond | 590 | | Lawrence D'Oliveiro |
1 May 24 | Re: Byte Addressability And Beyond | 431 | | John Levine |
1 May 24 | Re: Byte Addressability And Beyond | 409 | | Lawrence D'Oliveiro |
1 May 24 | Re: Byte Addressability And Beyond | 3 | | John Levine |
1 May 24 | Re: Byte Addressability And Beyond | 1 | | John Levine |
1 May 24 | Re: Byte Addressability And Beyond | 1 | | Lawrence D'Oliveiro |
1 May 24 | Re: Byte Addressability And Beyond | 1 | | Michael S |
1 May 24 | Re: Byte Addressability And Beyond | 404 | | John Levine |
2 May 24 | Re: Byte Addressability And Beyond | 382 | | Lawrence D'Oliveiro |
2 May 24 | Re: Byte Addressability And Beyond | 4 | | John Levine |
2 May 24 | Re: Byte Addressability And Beyond | 3 | | Lawrence D'Oliveiro |
2 May 24 | Re: Byte Addressability And Beyond | 2 | | John Levine |
5 May 24 | Re: Byte Addressability And Beyond | 1 | | Lawrence D'Oliveiro |
2 May 24 | Re: Byte Addressability And Beyond | 367 | | John Savard |
2 May 24 | Re: Byte Addressability And Beyond | 2 | | MitchAlsup1 |
11 May 24 | Re: Byte Addressability And Beyond | 1 | | John Savard |
4 May 24 | Re: Byte Addressability And Beyond | 364 | | Lawrence D'Oliveiro |
8 May 24 | Re: Byte Addressability And Beyond | 363 | | John Savard |
8 May 24 | Re: Byte Addressability And Beyond | 2 | | Lawrence D'Oliveiro |
10 May 24 | Re: Byte Addressability And Beyond | 1 | | David Brown |
8 May 24 | Re: Byte Addressability And Beyond | 360 | | MitchAlsup1 |
8 May 24 | Re: Byte Addressability And Beyond | 359 | | John Levine |
8 May 24 | Re: Byte Addressability And Beyond | 357 | | Lawrence D'Oliveiro |
9 May 24 | Re: Byte Addressability And Beyond | 356 | | John Levine |
10 May 24 | Re: Byte Addressability And Beyond | 354 | | David Brown |
10 May 24 | Re: Byte Addressability And Beyond | 353 | | Anton Ertl |
11 May 24 | Re: Byte Addressability And Beyond | 352 | | David Brown |
11 May 24 | Re: Byte Addressability And Beyond | 351 | | Anton Ertl |
11 May 24 | Re: Byte Addressability And Beyond | 158 | | David Brown |
11 May 24 | Re: Byte Addressability And Beyond | 1 | | Anton Ertl |
27 May 24 | Re: Byte Addressability And Beyond | 156 | | Lawrence D'Oliveiro |
27 May 24 | Re: Byte Addressability And Beyond | 155 | | John Levine |
27 May 24 | Re: Byte Addressability And Beyond | 154 | | Lawrence D'Oliveiro |
27 May 24 | Re: Byte Addressability And Beyond | 153 | | John Levine |
27 May 24 | Re: Byte Addressability And Beyond | 149 | | John Levine |
27 May 24 | Re: Byte Addressability And Beyond | 1 | | MitchAlsup1 |
28 May 24 | Re: Byte Addressability And Beyond | 147 | | Lawrence D'Oliveiro |
28 May 24 | Re: encoding conversion, Byte Addressability And Beyond | 1 | | John Levine |
28 May 24 | Re: Byte Addressability And Beyond | 145 | | Thomas Koenig |
29 May 24 | Re: Byte Addressability And Beyond | 137 | | Lawrence D'Oliveiro |
29 May 24 | Re: Byte Addressability And Beyond | 136 | | Anton Ertl |
29 May 24 | Re: Byte Addressability And Beyond | 12 | | Stefan Monnier |
29 May 24 | Re: Byte Addressability And Beyond | 10 | | Stefan Monnier |
29 May 24 | Re: Byte Addressability And Beyond | 3 | | John Levine |
30 May 24 | Re: Byte Addressability And Beyond | 2 | | George Neuner |
4 Jun 24 | Re: Byte Addressability And Beyond | 1 | | George Neuner |
30 May 24 | Re: Byte Addressability And Beyond | 6 | | Anton Ertl |
4 Jun 24 | Re: Byte Addressability And Beyond | 1 | | Lawrence D'Oliveiro |
4 Jun 24 | Re: Byte Addressability And Beyond | 4 | | Stefan Monnier |
7 Jun 24 | Re: Byte Addressability And Beyond | 1 | | Terje Mathisen |
7 Jun 24 | Re: Character non-equivalence, was Byte Addressability And Beyond | 2 | | John Levine |
9 Jun 24 | Re: Character non-equivalence, was Byte Addressability And Beyond | 1 | | Lawrence D'Oliveiro |
30 May 24 | Re: Byte Addressability And Beyond | 1 | | Lawrence D'Oliveiro |
30 May 24 | Re: Byte Addressability And Beyond | 117 | | Lawrence D'Oliveiro |
30 May 24 | Re: architectural goals, Byte Addressability And Beyond | 66 | | John Levine |
30 May 24 | Re: architectural goals, Byte Addressability And Beyond | 1 | | Stephen Fuld |
30 May 24 | Re: architectural goals, Byte Addressability And Beyond | 22 | | Anton Ertl |
30 May 24 | Re: architectural goals, Byte Addressability And Beyond | 21 | | Thomas Koenig |
30 May 24 | Re: architectural goals, Byte Addressability And Beyond | 8 | | Michael S |
30 May 24 | Re: architectural goals, Byte Addressability And Beyond | 1 | | Thomas Koenig |
30 May 24 | Re: IBM architectural goals, Byte Addressability And Beyond | 5 | | John Levine |
30 May 24 | Re: IBM architectural goals, Byte Addressability And Beyond | 2 | | Michael S |
30 May 24 | Re: IBM architectural goals, Byte Addressability And Beyond | 1 | | John Levine |
30 May 24 | Re: IBM architectural goals, Byte Addressability And Beyond | 2 | | Thomas Koenig |
30 May 24 | Re: IBM architectural goals, Byte Addressability And Beyond | 1 | | John Levine |
30 May 24 | Re: architectural goals, Byte Addressability And Beyond | 1 | | Anton Ertl |
30 May 24 | Re: architectural goals, Byte Addressability And Beyond | 3 | | Anton Ertl |
30 May 24 | Re: architectural goals, Byte Addressability And Beyond | 1 | | John Levine |
30 May 24 | Re: architectural goals, Byte Addressability And Beyond | 1 | | Thomas Koenig |
31 May 24 | Re: architectural goals, Byte Addressability And Beyond | 5 | | Terje Mathisen |
1 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 4 | | Thomas Koenig |
1 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 3 | | Anton Ertl |
2 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 2 | | John Levine |
4 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 1 | | Stefan Monnier |
4 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 4 | | Lawrence D'Oliveiro |
4 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 1 | | MitchAlsup1 |
4 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 1 | | Lynn Wheeler |
4 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 1 | | Stefan Monnier |
31 May 24 | Re: architectural goals, Byte Addressability And Beyond | 42 | | John Savard |
31 May 24 | Re: architectural goals, Byte Addressability And Beyond | 41 | | John Levine |
1 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 31 | | John Savard |
1 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 20 | | Thomas Koenig |
2 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 6 | | John Savard |
2 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 5 | | Thomas Koenig |
2 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 3 | | John Levine |
3 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 2 | | OrangeFish |
3 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 1 | | John Levine |
4 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 1 | | Lawrence D'Oliveiro |
4 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 13 | | Lawrence D'Oliveiro |
5 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 12 | | Lawrence D'Oliveiro |
5 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 1 | | Lawrence D'Oliveiro |
6 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 10 | | George Neuner |
6 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 6 | | John Levine |
7 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 4 | | Lawrence D'Oliveiro |
7 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 3 | | Stephen Fuld |
7 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 2 | | Lawrence D'Oliveiro |
7 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 1 | | Stephen Fuld |
7 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 1 | | Terje Mathisen |
6 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 1 | | Lynn Wheeler |
6 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 1 | | OrangeFish |
7 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 1 | | Lawrence D'Oliveiro |
2 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 10 | | John Dallman |
2 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 1 | | Michael S |
2 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 1 | | John Dallman |
4 Jun 24 | Re: architectural goals, Byte Addressability And Beyond | 7 | | Lawrence D'Oliveiro |
30 May 24 | Re: Byte Addressability And Beyond | 49 | | Stephen Fuld |
30 May 24 | Re: Byte Addressability And Beyond | 1 | | Anton Ertl |
30 May 24 | Re: Byte Addressability And Beyond | 2 | | Lawrence D'Oliveiro |
30 May 24 | Re: Byte Addressability And Beyond | 4 | | Terje Mathisen |
30 May 24 | Re: Byte Addressability And Beyond | 7 | | Terje Mathisen |
28 May 24 | Re: Byte Addressability And Beyond | 3 | | Lawrence D'Oliveiro |
12 May 24 | Re: python text, Byte Addressability And Beyond | 14 | | John Levine |
12 May 24 | Re: Byte Addressability And Beyond | 178 | | Thomas Koenig |
27 May 24 | Re: Byte Addressability And Beyond | 1 | | Lawrence D'Oliveiro |
8 May 24 | Re: Byte Addressability And Beyond | 1 | | Michael S |
2 May 24 | Re: Byte Addressability And Beyond | 10 | | MitchAlsup1 |
2 May 24 | Re: Byte Addressability And Beyond | 3 | | Michael S |
2 May 24 | Re: Byte Addressability And Beyond | 18 | | Anton Ertl |
1 May 24 | Byte Order (was: Byte Addressability And Beyond) | 4 | | Anton Ertl |
1 May 24 | Re: Byte Addressability And Beyond | 17 | | Stefan Monnier |
1 May 24 | Re: Byte Addressability And Beyond | 40 | | MitchAlsup1 |
1 May 24 | Re: Byte Addressability And Beyond | 15 | | Thomas Koenig |
1 May 24 | Re: Byte Addressability And Beyond | 3 | | Michael S |
2 May 24 | Re: Byte Addressability And Beyond | 4 | | Lawrence D'Oliveiro |
3 May 24 | Re: Byte Addressability And Beyond | 75 | | Anton Ertl |
5 May 24 | Re: Byte Addressability And Beyond | 20 | | John Savard |
5 May 24 | Re: Byte Addressability And Beyond | 1 | | John Savard |