Re: [dpdk-dev] [PATCH v2 2/3] config: add arm neoverse N1 SDP configuration

[Thomas Monjalon <thomas@monjalon.net>]

28/10/2019 04:24, Honnappa Nagarahalli:
> > 23/10/2019 07:03, Jerin Jacob:
> > > On Wed, Oct 23, 2019 at 2:37 AM Honnappa Nagarahalli
> > > <Honnappa.Nagarahalli@arm.com> wrote:
> > > > > > > On Thu, 2019-08-01 at 07:48 +0800, Gavin Hu wrote:
> > > > > > > > Arm N1 SDP is an infrastructure segment development platform
> > > > > > > > based on armv8.2-a Neoverse N1 CPU. For more information, refer
> > to:
> > > > > > > > https://community.arm.com/developer/tools-software/oss-platf
> > > > > > > > orms/w
> > > > > > > > /
> > > > > > > > docs/440/neoverse-n1-sdp
> > > > > > > >
> > > > > > > > Signed-off-by: Gavin Hu <gavin.hu@arm.com>
> > > > > > > > Reviewed-by: Honnappa Nagarahalli
> > > > > > > > <honnappa.nagarahalli@arm.com>
> > > > > > > > Reviewed-by: Steve Capper <steve.capper@arm.com>
> > > > > > > > ---
> > > > > > > > +CONFIG_RTE_MACHINE="neoversen1"
> > > > > > > This should probably be "n1sdp" as this is the name of the
> > > > > > > platform that matches the below configuration.
> > > > > > A clear definition of RTE_MACHINE is required. Jerin?
> > > > >
> > > > > I think, In the existing scheme of things, RTE_MACHINE defines,
> > > > > where to take the MACHINE_CFLAGS mk/machine/xxxx/rte.vars.mk
> > > > Ok, thank you
> > > >
> > > > >
> > > > > Considering the fact that there will be a lot of reusable IPs(for
> > > > > CPU) from ARM for  armv8, I think, it would make sense to
> > > > > introduce  RTE_MICRO_ARCH to avoid a lot of code duplications and
> > confusion.
> > > > >
> > > > > RTE_ARCH                             example: "x86" or "arm64"
> > > > > RTE_MICRO_ARCH               example: "a72" or "thunderx3" - defines
> > > > > mcpu and armv8 verion arch etc
> > > > > RTE_MACHINE                       example: "bluefield" or "thunderx3"
> > > > > - defines, number of cores, NUMA or not? etc
> > > > Looking at mk/machine/ directory, looks like RTE_MACHINE seems to be
> > defining micro-architecture for Intel. For ex: hsw, nhm, wsm. I see the same
> > for Arm as well.
> > > > Are you suggesting that we use RTE_MICRO_ARCH to pick mk/micro-
> > arch/xxxx/rte.vars.mk? and RTE_MACHINE would pick
> > mk/machine/xxxx/rte.vars.mk, but contain NUMA, #of cores etc?
> > >
> > > Yes for Make build. I think, it is deprecated soon, so we need a
> > > similar solution for meson.
> > 
> > Yes I would prefer we clean the mess in Meson, instead of talking about the
> > makefile system.
> > And honestly, N1 is not needed in the legacy makefile system.
> Unfortunately, most of the guys I talk to are still on makefile.

You need to help them to switch.
Adding new targets in meson-only can be a good motivation :)

> When is makefile system getting removed?

It must be clearly decided and announced.
The previous techboard discussions were about making makefile
hardly usable during 2020, i.e. very soon.

> > So focusing on config/arm/meson.build,
> > I think RTE_MACHINE is defined only for API compatibility with makefile.
> > However, I doubt this value is used by any application.
> > I think we can try to remove RTE_MACHINE from meson builds in DPDK 19.11,
> > or use RTE_MACHINE as micro-arch (my preference).
> 'MACHINE' means different things to different people, which is the root cause of this discussion.
> 'MICRO-ARCH' has a very clear meaning. Do you see any problem going with MICRO-ARCH instead?

Some applications may use RTE_MACHINE for this purpose.
It is part of the API since the befinning of DPDK.
I don't see a real motivation to break this API now.