Yes - Here's a quick blurb from some IBM doc I have on my PC:
"Simultaneous multithreading is the ability of a single physical
processor (core) to simultaneously dispatch instructions from more than
one hardware thread context. Because there are two hardware threads per
physical processor, additional instructions can run at the same time."
Beyond that, I have no idea how this works, or what workloads could
benefit from it.
On 9/1/2023 9:11 AM, Tony Harminc wrote:
On Fri, 1 Sept 2023 at 09:55, Scott Chapman
<000003fffd029d68-dmarc-requ...@listserv.ua.edu> wrote:
There are two levels of dispatching here: PR/SM dispatches zIIP cores for the
LPARs to use. Whether the LPAR uses both threads on that core or not depends on
the z/OS setting. With SMT enabled, it looks like you have twice as many zIIPs
as the LPAR has online zIIP cores. But (IIRC) the even-odd pairs are really two
threads on the same zIIP core.
I'm obviously missing something here, but since I don't do production
on Real Iron, I haven't been following SMT closely...
Jim's original question didn't mention zIIPs. Do PR/SM and z/OS not
follow similar rules for multi threading on CPs as for zIIPs? Is there
something inherently magic about zIIPs in this context, beyond that
z/OS won't routinely dispatch general work to them?
Tony H.
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