[dpdk-dev] [PATCH v4] build: optional NUMA and cpu counts detection

[Juraj Linkeš]

> -----Original Message-----
> From: Bruce Richardson <bruce.richardson at intel.com>
> Sent: Tuesday, June 29, 2021 1:29 PM
> To: Juraj Linkeš <juraj.linkes at pantheon.tech>
> Cc: thomas at monjalon.net; david.marchand at redhat.com;
> Honnappa.Nagarahalli at arm.com; Ruifeng.Wang at arm.com;
> ferruh.yigit at intel.com; jerinjacobk at gmail.com; dev at dpdk.org
> Subject: Re: [PATCH v4] build: optional NUMA and cpu counts detection
> 
> On Tue, Jun 29, 2021 at 12:55:05PM +0200, Juraj Linkeš wrote:
> > Add an option to automatically discover the host's numa and cpu counts
> > and use those values for a non cross-build.
> > Give users the option to override the per-arch default values or
> > values from cross files by specifying them on the command line with
> > -Dmax_lcores and -Dmax_numa_nodes.
> >
> > Signed-off-by: Juraj Linkeš <juraj.linkes at pantheon.tech>
> > Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli at arm.com>
> > ---
> Two very minor suggestions inline below.
> 
> Acked-by: Bruce Richardson <bruce.richardson at intel.com>
> 
> >
> <snip>
> > +max_lcores = get_option('max_lcores') if max_lcores == 'auto'
> 
> Rather than "auto", would "detect" be a clearer name for this option value?
> 
> <snip>
> > +option('max_lcores', type: 'string', value: 'default', description:
> > +       'Set maximum number of cores/threads supported by EAL. The
> > +default is different per-arch. Set to auto to detect the number of cores on the
> build machine.') option('max_numa_nodes', type: 'string', value: 'default',
> description:
> > +       'Set highest NUMA node supported by EAL. The default is
> > +different per-arch. Set to auto to detect the highest numa node on
> > +the build machine.')
> 
> I'd put the explicit values of "default" and "auto"(or "detect") in quotes "" to
> make clear they are literal values.
> 

Thanks, Bruce, I'll change it. I have one extra question now that I'm looking at the patch:
What does subprocess.run(['sysctl', '-n', 'vm.ndomains'], check=False) return exactly? Is the the number of NUMA nodes (looks like it) or the highest NUMA node on the system (the highest number of all NUMA nodes)? I'm asking because of how NUMA works on P9:
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):

Here we need not just two NUMA nodes, but at least 9 (0-8). Linux and Windows should return the highest NUMA, not sure about FreeBSD. Or maybe we should return the highest NUMA on which there are actual CPUs?