RE: [PATCH] config/x86: config support for AMD EPYC processors

["Morten Brørup" <mb@smartsharesystems.com>]

> From: Kevin Traynor [mailto:ktraynor@redhat.com]
> Sent: Tuesday, 17 October 2023 11.45
> 
> On 16/10/2023 06:20, Tummala, Sivaprasad wrote:
> > [AMD Official Use Only - General]
> >
> > Hi DPDK Techboard,
> >
> > Request to add this topic for discussion in the next techboard
> meeting.
> >
> 
> Hi Sivaprasad,
> 
> Are you or a representative (Ferruh?) able to attend the techboard
> meeting (3pm UTC Wednesday) to discuss this item?
> 
> thanks,
> Kevin.
> 
> > Thanks & Regards,
> > Sivaprasad
> >
> >> From: Tummala, Sivaprasad <Sivaprasad.Tummala@amd.com>
> >> Sent: Monday, October 16, 2023 10:44 AM
> >>
> >>> From: David Marchand <david.marchand@redhat.com>
> >>> Sent: Friday, October 6, 2023 1:21 PM
> >>>
> >>> On Mon, Sep 25, 2023 at 5:11 PM Sivaprasad Tummala
> >>> <sivaprasad.tummala@amd.com> wrote:
> >>>>
> >>>> From: Sivaprasad Tummala <Sivaprasad.Tummala@amd.com>
> >>>>
> >>>> By default, max lcores are limited to 128 for x86 platforms.
> >>>> On AMD EPYC processors, this limit needs to be increased to
> leverage
> >>>> all the cores.
> >>>>
> >>>> The patch adjusts the limit specifically for native compilation on
> >>>> AMD EPYC CPUs.
> >>>>
> >>>> Signed-off-by: Sivaprasad Tummala <Sivaprasad.Tummala@amd.com>
> >>>
> >>> This patch is a revamp of
> >>>
> >>
> http://inbox.dpdk.org/dev/BY5PR12MB3681C3FC6676BC03F0B42CCC96789@BY5PR
> >>> 12MB3681.namprd12.prod.outlook.com/
> >>> for which a discussion at techboard is supposed to have taken place.
> >>> But I didn't find a trace of it.
> >>>
> >>> One option that had been discussed in the previous thread was to
> >>> increase the max number of cores for x86.
> >>> I am unclear if this option has been properly evaluated/debatted.

Here are the minutes from the previous techboard discussions:
[1]: http://inbox.dpdk.org/dev/YZ43U36bFWHYClAi@platinum/
[2]: http://inbox.dpdk.org/dev/20211202112506.68acaa1a@hermes.local/

AFAIK, there has been no progress with dynamic max_lcores, so I guess the techboard's conclusion still stands:

There is no identified use-case where a single application requires more than 128 lcores. If a case a use-case exists for a single application that uses more than 128 lcores, the TB is ok to update the default config value.

> >>>
> >>> Can the topic be brought again at techboard?
> >>
> >> Hi David,
> >>
> >> The patch is intended to detect AMD platforms and enable all CPU
> cores by default
> >> on native builds.

This is done on native ARM builds, so why not on native X86 builds too?

> >>
> >> As an optimization for memory footprint, users can override this by
> specifying "-
> >> Dmax_lcores" option based on DPDK lcores required for their usecases.
> >>
> >> Sure, will request to add this topic for discussion at techboard.
> >>>
> >>> Thanks.
> >>>
> >>> --
> >>> David Marchand
> >