Re: [PATCH 1/2] sched/topology: Allow archs to override cpu_smt_mask

From: Srikar Dronamraju
Date: Thu Aug 06 2020 - 12:43:31 EST

* peterz@xxxxxxxxxxxxx <peterz@xxxxxxxxxxxxx> [2020-08-06 15:15:47]:

> > But my understanding is most LPARs don't get migrated back and forth,
> > they'll start life on a P8 and only get migrated to a P9 once when the
> > customer gets a P9. They might then run for a long time (months to
> > years) on the P9 in P8 compat mode, not because they ever want to
> > migrate back to a real P8, but because the software in the LPAR is still
> > expecting to be on a P8.
> >
> > I'm not a real expert on all the Enterprisey stuff though, so someone
> > else might be able to give us a better picture.
> >
> > But the point of mentioning the migration stuff was mainly just to
> > explain why we feel we need to present SMT8 to userspace even on P9.
> OK, fair enough. The patch wasn't particularly onerous, I was just
> wondering why etc..
> The case of starting on a P8 and being migrated to a P9 makes sense to
> me; in that case you'd like to rebuild your sched domains, but can't go
> about changing user visible topolofy information.
> I suppose:
> Acked-by; Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> An updated Changelog that recaps some of this discussion might also be
> nice.

Okay, will surely do the needful.

Thanks and Regards
Srikar Dronamraju