Re: "Mini" tags to reduce the number of op codes

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Sujet : Re: "Mini" tags to reduce the number of op codes
De : mitchalsup (at) *nospam* aol.com (MitchAlsup1)
Groupes : comp.arch
Date : 12. Apr 2024, 00:12:25
Autres entêtes
Organisation : Rocksolid Light
Message-ID : <e4443c417f7145d65b04bec48160c629@www.novabbs.org>
References : 1 2 3 4 5 6 7 8 9 10 11 12 13
User-Agent : Rocksolid Light
Scott Lurndal wrote:

"Paul A. Clayton" <paaronclayton@gmail.com> writes:
On 4/9/24 8:28 PM, MitchAlsup1 wrote:
BGB-Alt wrote:
[snip]
Things like memcpy/memmove/memset/etc, are function calls in cases when not directly transformed into register load/store sequences.
 My 66000 does not convert them into LD-ST sequences, MM is a single instruction.
>
I wonder if it would be useful to have an immediate count form of
memory move. Copying fixed-size structures would be able to use an
immediate. Aside from not having to load an immediate for such
cases, there might be microarchitectural benefits to using a
constant. Since fixed-sized copies would likely be limited to
smaller regions (with the possible exception of 8 MiB page copies)
and the overhead of loading a constant for large sizes would be
tiny, only providing a 16-bit immediate form might be reasonable.

It seems to me that an offloaded DMA engine would be a far
better way to do memmove (over some threshhold, perhaps a
cache line) without trashing the caches.   Likewise memset.
Effectively, that is what HW does, even on the lower end machines,
the AGEN unit of the Cache access pipeline is repeatedly cycled,
and data is read and/or written. One can execute instructions not
needing memory references while LDM, STM, ENTER, EXIT, MM, and MS
are in progress.
Moving this sequencer farther out would still require it to consume
all L1 BW in any event (snooping) for memory consistency reasons.
{Note: cache accesses are performed line-wide not register width wide}

>
Did end up with an intermediate "memcpy slide", which can handle medium size memcpy and memset style operations by branching into a slide.
 MMs and MSs that do not cross page boundaries are ATOMIC. The entire system
sees only the before or only the after state and nothing in between.

One might wonder how that atomicity is guaranteed in a
SMP processor...
The entire chunk of data traverses the interconnect as a single
transaction. All interested 3rd parties (not originator nor
recipient) see either the memory state before the transfer or
after the transfer.

Date Sujet#  Auteur
3 Apr 24 * "Mini" tags to reduce the number of op codes81Stephen Fuld
3 Apr 24 +* Re: "Mini" tags to reduce the number of op codes8Anton Ertl
15 Apr 24 i+* Re: "Mini" tags to reduce the number of op codes6MitchAlsup1
15 Apr 24 ii`* Re: "Mini" tags to reduce the number of op codes5Terje Mathisen
15 Apr 24 ii +- Re: "Mini" tags to reduce the number of op codes1Terje Mathisen
15 Apr 24 ii `* Re: "Mini" tags to reduce the number of op codes3MitchAlsup1
16 Apr 24 ii  `* Re: "Mini" tags to reduce the number of op codes2Terje Mathisen
16 Apr 24 ii   `- Re: "Mini" tags to reduce the number of op codes1MitchAlsup1
17 Apr 24 i`- Re: "Mini" tags to reduce the number of op codes1Stephen Fuld
3 Apr 24 +* Re: "Mini" tags to reduce the number of op codes3Thomas Koenig
17 Apr 24 i`* Re: "Mini" tags to reduce the number of op codes2Stephen Fuld
17 Apr 24 i `- Re: "Mini" tags to reduce the number of op codes1BGB-Alt
3 Apr 24 +* Re: "Mini" tags to reduce the number of op codes12BGB-Alt
3 Apr 24 i+* Re: "Mini" tags to reduce the number of op codes9MitchAlsup1
4 Apr 24 ii+* Re: "Mini" tags to reduce the number of op codes7Terje Mathisen
4 Apr 24 iii+* Re: "Mini" tags to reduce the number of op codes3Michael S
4 Apr 24 iiii`* Re: "Mini" tags to reduce the number of op codes2Terje Mathisen
4 Apr 24 iiii `- Re: "Mini" tags to reduce the number of op codes1Michael S
5 Apr 24 iii`* Re: "Mini" tags to reduce the number of op codes3BGB-Alt
5 Apr 24 iii `* Re: "Mini" tags to reduce the number of op codes2MitchAlsup1
5 Apr 24 iii  `- Re: "Mini" tags to reduce the number of op codes1BGB
17 Apr 24 ii`- Re: "Mini" tags to reduce the number of op codes1Stephen Fuld
3 Apr 24 i`* Re: "Mini" tags to reduce the number of op codes2MitchAlsup1
4 Apr 24 i `- Re: "Mini" tags to reduce the number of op codes1BGB
5 Apr 24 +* Re: "Mini" tags to reduce the number of op codes54John Savard
5 Apr 24 i+- Re: "Mini" tags to reduce the number of op codes1BGB-Alt
5 Apr 24 i`* Re: "Mini" tags to reduce the number of op codes52MitchAlsup1
7 Apr 24 i `* Re: "Mini" tags to reduce the number of op codes51John Savard
7 Apr 24 i  +* Re: "Mini" tags to reduce the number of op codes6MitchAlsup1
8 Apr 24 i  i`* Re: "Mini" tags to reduce the number of op codes5John Savard
8 Apr 24 i  i +* Re: "Mini" tags to reduce the number of op codes2Thomas Koenig
17 Apr 24 i  i i`- Re: "Mini" tags to reduce the number of op codes1John Savard
8 Apr 24 i  i `* Re: "Mini" tags to reduce the number of op codes2MitchAlsup1
17 Apr 24 i  i  `- Re: "Mini" tags to reduce the number of op codes1John Savard
7 Apr 24 i  `* Re: "Mini" tags to reduce the number of op codes44Thomas Koenig
7 Apr 24 i   `* Re: "Mini" tags to reduce the number of op codes43MitchAlsup1
8 Apr 24 i    `* Re: "Mini" tags to reduce the number of op codes42Thomas Koenig
8 Apr 24 i     +- Re: "Mini" tags to reduce the number of op codes1Anton Ertl
9 Apr 24 i     `* Re: "Mini" tags to reduce the number of op codes40Thomas Koenig
9 Apr 24 i      +* Re: "Mini" tags to reduce the number of op codes38BGB
9 Apr 24 i      i`* Re: "Mini" tags to reduce the number of op codes37MitchAlsup1
10 Apr 24 i      i `* Re: "Mini" tags to reduce the number of op codes36BGB-Alt
10 Apr 24 i      i  +* Re: "Mini" tags to reduce the number of op codes31MitchAlsup1
10 Apr 24 i      i  i+* Re: "Mini" tags to reduce the number of op codes23BGB
10 Apr 24 i      i  ii`* Re: "Mini" tags to reduce the number of op codes22MitchAlsup1
10 Apr 24 i      i  ii +* Re: "Mini" tags to reduce the number of op codes3BGB-Alt
10 Apr 24 i      i  ii i`* Re: "Mini" tags to reduce the number of op codes2MitchAlsup1
11 Apr 24 i      i  ii i `- Re: "Mini" tags to reduce the number of op codes1BGB
10 Apr 24 i      i  ii +- Re: "Mini" tags to reduce the number of op codes1BGB-Alt
11 Apr 24 i      i  ii +* Re: "Mini" tags to reduce the number of op codes16MitchAlsup1
11 Apr 24 i      i  ii i`* Re: "Mini" tags to reduce the number of op codes15Michael S
11 Apr 24 i      i  ii i `* Re: "Mini" tags to reduce the number of op codes14BGB
11 Apr 24 i      i  ii i  `* Re: "Mini" tags to reduce the number of op codes13MitchAlsup1
11 Apr 24 i      i  ii i   +* Re: "Mini" tags to reduce the number of op codes9BGB-Alt
12 Apr 24 i      i  ii i   i`* Re: "Mini" tags to reduce the number of op codes8MitchAlsup1
12 Apr 24 i      i  ii i   i `* Re: "Mini" tags to reduce the number of op codes7BGB
12 Apr 24 i      i  ii i   i  `* Re: "Mini" tags to reduce the number of op codes6MitchAlsup1
12 Apr 24 i      i  ii i   i   `* Re: "Mini" tags to reduce the number of op codes5BGB
13 Apr 24 i      i  ii i   i    +- Re: "Mini" tags to reduce the number of op codes1MitchAlsup1
13 Apr 24 i      i  ii i   i    `* Re: "Mini" tags to reduce the number of op codes3MitchAlsup1
13 Apr 24 i      i  ii i   i     +- Re: "Mini" tags to reduce the number of op codes1BGB
15 Apr 24 i      i  ii i   i     `- Re: "Mini" tags to reduce the number of op codes1BGB-Alt
12 Apr 24 i      i  ii i   `* Re: "Mini" tags to reduce the number of op codes3Michael S
12 Apr 24 i      i  ii i    +- Re: "Mini" tags to reduce the number of op codes1Michael S
15 Apr 24 i      i  ii i    `- Re: "Mini" tags to reduce the number of op codes1MitchAlsup1
11 Apr 24 i      i  ii `- Re: "Mini" tags to reduce the number of op codes1Terje Mathisen
11 Apr 24 i      i  i`* Re: "Mini" tags to reduce the number of op codes7Paul A. Clayton
11 Apr 24 i      i  i +- Re: "Mini" tags to reduce the number of op codes1BGB
11 Apr 24 i      i  i +* Re: "Mini" tags to reduce the number of op codes2BGB-Alt
12 Apr 24 i      i  i i`- Re: "Mini" tags to reduce the number of op codes1MitchAlsup1
12 Apr 24 i      i  i +* Re: "Mini" tags to reduce the number of op codes2MitchAlsup1
21 Apr 24 i      i  i i`- Re: "Mini" tags to reduce the number of op codes1Paul A. Clayton
21 Apr 24 i      i  i `- Re: "Mini" tags to reduce the number of op codes1Paul A. Clayton
10 Apr 24 i      i  `* Re: "Mini" tags to reduce the number of op codes4Chris M. Thomasson
10 Apr 24 i      i   `* Re: "Mini" tags to reduce the number of op codes3BGB
10 Apr 24 i      i    `* Re: "Mini" tags to reduce the number of op codes2Chris M. Thomasson
10 Apr 24 i      i     `- Re: "Mini" tags to reduce the number of op codes1BGB-Alt
13 Apr 24 i      `- Re: "Mini" tags to reduce the number of op codes1Brian G. Lucas
15 Apr 24 +- Re: "Mini" tags to reduce the number of op codes1MitchAlsup1
17 Apr 24 `* Re: "Mini" tags to reduce the number of op codes2Stephen Fuld
17 Apr 24  `- Re: "Mini" tags to reduce the number of op codes1MitchAlsup1

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