Re: [dpdk-dev] [PATCH v5] build: optional NUMA and cpu counts detection

["Juraj Linkeš" <juraj.linkes@pantheon.tech>]

> -----Original Message-----
> From: Bruce Richardson <bruce.richardson@intel.com>
> Sent: Tuesday, August 31, 2021 10:03 AM
> To: Juraj Linkeš <juraj.linkes@pantheon.tech>
> Cc: Piotr Kubaj <pkubaj@anongoth.pl>; David Christensen
> <drc@linux.vnet.ibm.com>; thomas@monjalon.net;
> david.marchand@redhat.com; Honnappa.Nagarahalli@arm.com;
> Ruifeng.Wang@arm.com; ferruh.yigit@intel.com; jerinjacobk@gmail.com;
> jerinj@marvell.com; stephen@networkplumber.org; dev@dpdk.org
> Subject: Re: [PATCH v5] build: optional NUMA and cpu counts detection
> 
> On Tue, Aug 31, 2021 at 07:54:16AM +0000, Juraj Linkeš wrote:
> >
> >
> > > -----Original Message-----
> > > From: Piotr Kubaj <pkubaj@anongoth.pl>
> > > Sent: Tuesday, August 31, 2021 2:55 AM
> > > To: Juraj Linkeš <juraj.linkes@pantheon.tech>
> > > Cc: David Christensen <drc@linux.vnet.ibm.com>; thomas@monjalon.net;
> > > david.marchand@redhat.com; bruce.richardson@intel.com;
> > > Honnappa.Nagarahalli@arm.com; Ruifeng.Wang@arm.com;
> > > ferruh.yigit@intel.com; jerinjacobk@gmail.com; jerinj@marvell.com;
> > > stephen@networkplumber.org; dev@dpdk.org
> > > Subject: Re: [PATCH v5] build: optional NUMA and cpu counts
> > > detection
> > >
> > > Hi,
> > >
> > > sorry for the late answer.
> >
> > Thanks for the answer anyway, better late than never.
> >
> > >
> > > I suppose you mean sysctl command, not systemctl.
> > >
> >
> > That's right. What does lscpu say? Are the NUMA nodes non-contiguous like
> this?:
> > NUMA node0 CPU(s):   0-63
> > NUMA node8 CPU(s):   64-127
> > NUMA node252 CPU(s):
> > NUMA node253 CPU(s):
> > NUMA node254 CPU(s):
> > NUMA node255 CPU(s):
> >
> > > On dual CPU systems, it returns 2. On single CPU ones, 1.
> >
> > I asked the previous question so that we know the actual numa node number
> of the second CPU. If it's 8, then sysctl does some renumeration and we can't
> use it.
> >
> > Bruce, maybe we should just parse lscpu output? That introduces a
> dependency, but that may not be such a big deal as lscpu is pretty common.
> >
> Until we are sure that we need it, can we just keep things simple? Perhaps we
> can use lscpu if present, and fallback to sysctl output if not.

Piotr says lscpu isn't available on ppc FreeBSD. I think this leaves us with two options:
1. either use sysctl with the risk that it may not return an accurate value
2. not support PPC for numa detection

What do you think?