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

[Bruce Richardson <bruce.richardson@intel.com>]

On Fri, Jul 16, 2021 at 01:53:18PM +0000, Juraj Linkeš wrote:
> 
> 
> > -----Original Message-----
> > From: David Christensen <drc@linux.vnet.ibm.com>
> > Sent: Tuesday, July 6, 2021 8:11 PM
> > To: Bruce Richardson <bruce.richardson@intel.com>; Juraj Linkeš
> > <juraj.linkes@pantheon.tech>
> > Cc: thomas@monjalon.net; david.marchand@redhat.com;
> > Honnappa.Nagarahalli@arm.com; Ruifeng.Wang@arm.com;
> > ferruh.yigit@intel.com; jerinjacobk@gmail.com; dev@dpdk.org
> > Subject: Re: [dpdk-dev] [PATCH v4] build: optional NUMA and cpu counts
> > detection
> > 
> > 
> > 
> > On 7/6/21 2:08 AM, Bruce Richardson wrote:
> > > On Tue, Jul 06, 2021 at 08:56:37AM +0000, Juraj Linkeš wrote:
> > >>
> > >>
> > >>> -----Original Message-----
> > >>> From: Bruce Richardson <bruce.richardson@intel.com>
> > >>> Sent: Tuesday, June 29, 2021 1:29 PM
> > >>> To: Juraj Linkeš <juraj.linkes@pantheon.tech>
> > >>> Cc: thomas@monjalon.net; david.marchand@redhat.com;
> > >>> Honnappa.Nagarahalli@arm.com; Ruifeng.Wang@arm.com;
> > >>> ferruh.yigit@intel.com; jerinjacobk@gmail.com; dev@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@pantheon.tech>
> > >>>> Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> > >>>> ---
> > >>> Two very minor suggestions inline below.
> > >>>
> > >>> Acked-by: Bruce Richardson <bruce.richardson@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?
> > >
> > > I'm not sure, and I think to be really sure we'd need it tested on a
> > > P9 system. The help text for the sysctl node says "Number of physical
> > > memory domains available", which would imply 2 in the case above.
> > > [However, we also would need to find out how BSD numbers the domains,
> > > too, as it's possible an OS could just call them 0 and 1, rather than
> > > 0 and 8 if it wanted to.]
> > >
> > > In short, we'd need to test to be sure. Is FreeBSD on P9 a supported
> > > config, and if so can the P9 maintainer perhaps help out with testing?
> > 
> > Results of the v4 patch on an IBM AC922 P9 system with Linux:
> > 
> 
> Can you get results from FreeBSD as well?
> 
> > $ python3 get-numa-count.py
> > 8
> > NUMA node0 CPU(s):   0-63
> > NUMA node8 CPU(s):   64-127
> <snip>
> Is this the right number for your case, i.e. are you able to use both numa nodes when RTE_MAX_NUMA_NODES=8?
> 
> Or maybe this is a question for Bruce or Thomas - what do we need to set in RTE_MAX_NUMA_NODES to be able to use all numa nodes on the system? The highest numa node number or that + 1? In linux, with 4 numa nodes, there will be node0-node3 under /sys/devices/system/node - do we need to set RTE_MAX_NUMA_NODES to 3 or 4?
>

4, I believe.