On Fri, Sep 15, 2017 at 02:39:16PM +0530, Nikunj A Dadhania wrote: > David Gibson <da...@gibson.dropbear.id.au> writes: > > > On Fri, Sep 15, 2017 at 01:53:15PM +0530, Nikunj A Dadhania wrote: > >> David Gibson <da...@gibson.dropbear.id.au> writes: > >> > >> >> > >> >> I thought, I am doing the same here for PowerNV, number of online cores > >> >> is equal to initial online vcpus / threads per core > >> >> > >> >> int boot_cores_nr = smp_cpus / smp_threads; > >> >> > >> >> Only difference that I see in PowerNV is that we have multiple chips > >> >> (max 2, at the moment) > >> >> > >> >> cores_per_chip = smp_cpus / (smp_threads * pnv->num_chips); > >> > > >> > This doesn't make sense to me. Cores per chip should *always* equal > >> > smp_cores, you shouldn't need another calculation for it. > >> > > >> >> And in case user has provided sane smp_cores, we use it. > >> > > >> > If smp_cores isn't sane, you should simply reject it, not try to fix > >> > it. That's just asking for confusion. > >> > >> This is the case where the user does not provide a topology(which is a > >> valid scenario), not sure we should reject it. So qemu defaults > >> smp_cores/smt_threads to 1. I think it makes sense to over-ride. > > > > If you can find a way to override it by altering smp_cores when it's > > not explicitly specified, then ok. > > Should I change the global smp_cores here as well ?
I'm pretty uneasy with that option. It would take a fair bit of
checking to ensure that changing smp_cores is safe here. An easier to
verify option would be to make the generic logic which splits up an
unspecified -smp N into cores and sockets more flexible, possibly
based on machine options for max values.
That might still be more trouble than its worth.
> > But overriding smp_cores with a different variable that's the "real"
> > number of cores is not acceptable. If that means the user has to
> > specify cores explicitly, so be it.
>
> Right, we would error out in case there is mismatch.
>
> > Slight awkwardness in command line is preferable to breaking the
> > assumption that smp_cores == (# of cores per next level up cpu object)
> > which is used all over the place.
>
> Regards
> Nikunj
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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