> > > > > > >> From: Tummala, Sivaprasad <sivaprasad.tumm...@amd.com> > > > > > > >>> From: David Marchand <david.march...@redhat.com> > > > > > > >>> On Mon, Sep 25, 2023 at 5:11 PM Sivaprasad Tummala > > > > > > >>>> From: Sivaprasad Tummala <sivaprasad.tumm...@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.tumm...@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. > > > > > > > > This is the summary of the techboard meeting: > > > > (see https://mails.dpdk.org/archives/dev/2023-October/279672.html) > > > > > > > > - There is some asks for more than 128 worker cores > > > > - Discussion about generally increasing the default max core count > > and > > > > trade-offs with memory consumption but this is longer term issue > > > > > > The distros are currently satisfied with the 128 cores default, so > > the decision here was: Leave the 128 cores default as is, for now. > > > > > > Any long term improvements regarding memory consumption of many-core > > systems are not relevant for this patch. > > > > > > > - Acceptance for the direction of this patch in the short term > > > > > > With the twist that it must work for cross compile. It is the > > properties of the target CPU that matter, not the properties of the > > host > > > CPU. (Although the build may be "native", i.e. the target CPU is the > > same as the host CPU, it is still the target CPU that matters.) > > > > > > > - Details of whether it should be for EPYC only or x86 to be > > figured > > > > out > > > > on mailing list > > > > > > I think this is obvious... > > > > > > ARM already provides ARM CPU specific optimizations. > > > AMD should be allowed to provide AMD CPU specific optimizations too. > > > Intel can also provide Intel CPU specific optimizations. > > > > I suppose no-one stopping AMD/Intel/ARM to provide their CPU specific > > optimizations. > > Though as end-user, my preference would be to have one generic build > > (machine=default) that would work ok > > on all cpus for given architecture (let say x86) instead of > > maintaining/testing dozens of different flavors. > > Agree. Machine specific builds should be explicitly specified. I consider > "native" a variant of explicitly specifying the target machine. > > > I suppose for 23.11 we have not much choice but accept that patch as it > > is. > > No. They agreed in the techboard meeting to rework it for cross compile.
Ah, yes, cross-builds, nearly forgot about them. I suppose yes, you are right, it needs to be supported for completeness. > > > Though I think in future (24.11?) it would be ideal to make > > RTE_MAX_LCORE a runtime parameter and > > remove it from public API structs. > > It is probably more difficult than it sounds to fully remove RTE_MAX_LCORE. I am not saying it is not an easy one, otherwise probably it will be already done. > However, if we could make it mostly a runtime parameter, and only keep > RTE_MAX_LCORE in arrays of small structures, we could > increase it to some very large (but still sane) value, like 4096 or whatever > number of CPU cores can be found in the largest system out > there. > > > > > > > > And if some of these optimizations are rooted in the same criteria, > > they should be shared across the relevant CPU architectures. We > > > follow this principle in the source code files, and the principle > > also applies to the build files. > > > > > > > > > > > So now let's figure out the details please. > > > > Suggestions? > > > > > > Suggestions provided inline above. :-)
