Re: Inside an IBM z17

In article <vv9fdc$3mhk4$1@dont-email.me>,
Lawrence D'Oliveiro  <ldo@nz.invalid> wrote:

On Sun, 4 May 2025 20:53:42 -0400 (EDT), Scott Dorsey wrote:
>

You should check out Martin's "Design of Real-Time Computer Systems"
which was written in the early days of SAABRE and other transaction
processing systems.

>
Their idea of real time was responding in a few seconds, before the user
got frustrated enough to hit SEND again.

Today we would call those "interactive systems," yes.  Not the same as
true realtime systems with deadlines.

Meanwhile, Linux recently mainlined the PREEMPT_RT patches, where the
definition of real time is being able to provide sub-millisecond
response to playing or recording sound samples for pro audio.

That's still not hard realtime at all, but it gives you reduced latency,
realtime scheduling, and the ability to preempt kernel threads.  That
latter one has become a big deal since som much crap has been rolled into
the kernel.

But what they mean by "RT" isn't what hard realtime people mean by "RT"
which has nothing to do with what the transaction processing guys meant
as "RT."  Do not get hung up on words, especially when people use the same
words for rather different concepts.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."