Re: [PATCH v6 00/21] arch_topology: Updates to add socket support and fix cluster ids

Conor.Dooley
2022-07-05T20:16:10Z

On 05/07/2022 21:07, Sudeep Holla wrote:
> On Tue, Jul 05, 2022 at 07:06:17PM +0000, Conor.Dooley@microchip.com wrote:
>> [Adding back the CC list from the original thread]
>>
>> On 05/07/2022 13:27, Brice Goglin wrote:
>>> [You don't often get email from brice.goglin@inria.fr. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
>>>
>>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>>
>>> Hello Conor
>>>
>>> I am the main developer of hwloc [1] which is used by many people to
>>> detect the topology of servers. We're started to see some users of hwloc
>>> on RISC-V and we got some reports about the topology exposed by
>>> Linux/sysfs being wrong on some platforms.
>>>
>>> For instance https://github.com/open-mpi/hwloc/issues/536 says HiFive
>>> Unmatched with SiFive Freedom U740 running Linux 5.15 exposes a single
>>> core with 4 threads instead of 4 cores, while StarFive VisionFive v1
>>> with JH7100 running 5.18.5 correctly exposes 2 cores.
>>
>> And with Sudeep's patches applied I get (next-20220704):
>> # hwloc-calc -N core all
>> 1
>> # hwloc-calc -N pu all
>> 4
>> On a PolarFire SoC (so the same as a SiFive U540).
>> So unfortunately, these patches are not the fix you seek!
>>
>
> Not sure what you mean by that ?

Nothing meaningful really, just saying that this patchset
was unrelated to the problem he reported his response to
it.

>
>> Wracked my brains for a bit, but could not see any differences
>> between the U740 and the JH7100. Culprit seems to be the lack
>> of a cpu-map node (which is only present in the downstream dt).
>>
>
> Indeed, the topology depends on /cpu-map node. However on ARM64 we do
> have fallback settings in absence of /cpu-map node so that it is handled
> correctly. I wasn't sure what was or can be done on RISC-V as /cpu-map
> is optional.
>
>> I've sent patches for the upstream devicetrees:
>> https://lore.kernel.org/linux-riscv/20220705190435.1790466-1-mail@conchuod.ie/
>>
>
> I will take a look.
>
>>> Does it depend a lot on the platform because
>>> device-tree and/or ACPI aren't always properly filled by vendors?
>
> Absolutely.
>
>>> Does it depend a lot on the Linux kernel version?
>
> Ideally not much, but hey we had some issues on Arm64 too which this series
> is addressing.
>
>>> Should I expect significant improvements for both in the next months?
>
> Not much in topology or nothing planned. I have no idea on NUMA
>
>
> Hi Conor,
>
> I would have preferred you to add me to the original thread and referred
> this thread from there. I don't want to derail the discussion in this
> thread as nothing much can be done here.

This is the original thread! It was just one off-list email that was a
to me only response to this arch_topologu thread that you can see here

But yeah - should have CCed you on the cpu-map stuff too.