Re: [dpdk-dev] [PATCH 2/2] build: establish an invariant machine type

[Christian Ehrhardt <christian.ehrhardt@canonical.com>]

On Wed, Nov 14, 2018 at 1:05 PM Luca Boccassi <bluca@debian.org> wrote:
>
> On Wed, 2018-11-14 at 11:52 +0000, Bruce Richardson wrote:
> > On Wed, Nov 14, 2018 at 11:40:11AM +0000, Luca Boccassi wrote:
> > > On Wed, 2018-11-14 at 12:34 +0100, Christian Ehrhardt wrote:
> > > > Add the machine definition 'baseline' which is special compared
> > > > to 'native' (most optimized for current system) or any explicit
> > > > type (external entity has to decide on the type).
> > > >
> > > > It defaults to the per arch agreed common minimal baseline
> > > > needed for DPDK to reasonable work.
> > > >
> > > > That might not be the most optimized, but the most portable
> > > > version while still being able to support the CPU features
> > > > required for DPDK.
> > > >
> > > > Going forward this can be bumped up by the DPDK project, but it
> > > > can never be an invariant like 'native'.
> > > >
> > > > Distributions and other needing portable code are expected to
> > > > define the machine as 'baseline'.
> > > >
> > > > Signed-off-by: Christian Ehrhardt <christian.ehrhardt@canonical.c
> > > > om>
> > > > ---
> > > >  config/meson.build | 21 +++++++++++++++++++++
> > > >  1 file changed, 21 insertions(+)
> > > >
> > > > diff --git a/config/meson.build b/config/meson.build
> > > > index 1af305f46..23f612457 100644
> > > > --- a/config/meson.build
> > > > +++ b/config/meson.build
> > > > @@ -7,6 +7,27 @@ if meson.is_cross_build()
> > > >  else
> > > >   machine = get_option('machine')
> > > >  endif
> > > > +
> > > > +# machine type 'baseline' is special, it defaults to the per
> > > > arch
> > > > agreed common
> > > > +# minimal baseline needed for DPDK.
> > > > +# That might not be the most optimized, but the most portable
> > > > version while
> > > > +# still being able to support the CPU features required for
> > > > DPDK.
> > > > +# This can be bumped up by the DPDK project, but it can never be
> > > > an
> > > > +# invariant like 'native'
> > > > +if machine == 'baseline'
> > > > + if host_machine.cpu_family().startswith('x86')
> > > > +         # matches the old pre-meson build systems
> > > > default
> > > > +         machine = 'corei7'
> > > > + elif host_machine.cpu_family().startswith('arm')
> > > > +         machine = 'armv7a'
> > > > + elif host_machine.cpu_family().startswith('aarch')
> > > > +         # arm64 manages defaults in
> > > > config/arm/meson.build
> > > > +         machine = 'default'
> > > > + elif host_machine.cpu_family().startswith('ppc')
> > > > +         machine = 'power8'
> > > > + endif
> > > > +endif
> > > > +
> > > >  dpdk_conf.set('RTE_MACHINE', machine)
> > > >  machine_args = []
> > >
> > > Acked-by: Luca Boccassi <bluca@debian.org>
> > >
> >
> > No objection in principle, but, for alignment with make build system,
> > do we
> > want to call this "default" instead? Given a clean slate, "baseline"
> > is more
> > descriptive, but make already uses "default" for this. Perhaps
> > support
> > both?
> >
> > /Bruce
>
> I'm fine with both - but if make already has default, it makes sense to
> keep it consistent.

Yeah I agree for consistency, I just need to check for a v2 if none of
them will misuse default to become native again

> --
> Kind regards,
> Luca Boccassi



-- 
Christian Ehrhardt
Software Engineer, Ubuntu Server
Canonical Ltd