* [TUHS] XID register
@ 2023-12-03 6:01 ron minnich
2024-01-10 4:22 ` [TUHS] " Rico Pajarola
0 siblings, 1 reply; 2+ messages in thread
From: ron minnich @ 2023-12-03 6:01 UTC (permalink / raw)
To: The Eunuchs Hysterical Society
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SunRPC, among other protocols, needs transaction IDs (XIDs) to distinguish
RPCs.For SunRPC, it's important that XIDs not be reused (not for all
protocols; 9p has no such requirement). Stateless protocols like NFS and
reused XIDs can get messy.
There is a vague, 30 year old memory, I have, that at some point SPARC got
a time register, or some other register, that always provided a different
answer each time it was read, even if read back to back, in part to enable
creation of non-reused XIDs. Note that things like the TSC or RISC-V MTIME
register make no such guarantee.
I am pretty sure someone here can fill me in, or tell me I'm wrong, about
my SPARC memory.
thanks
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* [TUHS] Re: XID register
2023-12-03 6:01 [TUHS] XID register ron minnich
@ 2024-01-10 4:22 ` Rico Pajarola
0 siblings, 0 replies; 2+ messages in thread
From: Rico Pajarola @ 2024-01-10 4:22 UTC (permalink / raw)
To: ron minnich; +Cc: The Eunuchs Hysterical Society
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SPARCv9 has %tick register which just counts up on each clock cycle. Older
SPARCs don't have that. I'd still suspect you'd get non-unique results in a
multi CPU machine without additional effort.
On Sat, Dec 2, 2023 at 10:02 PM ron minnich <rminnich@gmail.com> wrote:
> SunRPC, among other protocols, needs transaction IDs (XIDs) to distinguish
> RPCs.For SunRPC, it's important that XIDs not be reused (not for all
> protocols; 9p has no such requirement). Stateless protocols like NFS and
> reused XIDs can get messy.
>
> There is a vague, 30 year old memory, I have, that at some point SPARC got
> a time register, or some other register, that always provided a different
> answer each time it was read, even if read back to back, in part to enable
> creation of non-reused XIDs. Note that things like the TSC or RISC-V MTIME
> register make no such guarantee.
>
> I am pretty sure someone here can fill me in, or tell me I'm wrong, about
> my SPARC memory.
>
> thanks
>
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