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

[David Christensen <drc@linux.vnet.ibm.com>]

On 7/16/21 6:53 AM, 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?

I can't help with FreeBSD here, I only have Linux on systems within IBM.

> 
>> $ 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?

node8 above is the ninth NUMA node so I'd need to use 
RTE_MAX_NUMA_NODES=9 as a minimum so that any arrays using that value 
are adequately sized.

Dave