Re: [dpdk-dev] [PATCH v4 3/3] build: add option to enable wait until equal

From: Thomas Monjalon <thomas@monjalon.net>
To: Ruifeng Wang <Ruifeng.Wang@arm.com>, Jerin Jacob <jerinjacobk@gmail.com>
Cc: Bruce Richardson <bruce.richardson@intel.com>,
	Jan Viktorin <viktorin@rehivetech.com>,
	"jerinj@marvell.com" <jerinj@marvell.com>,
	"dev@dpdk.org" <dev@dpdk.org>,
	"david.marchand@redhat.com" <david.marchand@redhat.com>,
	nd <nd@arm.com>,
	Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>
Subject: Re: [dpdk-dev] [PATCH v4 3/3] build: add option to enable wait until equal
Date: Thu, 08 Jul 2021 09:32:57 +0200	[thread overview]
Message-ID: <4337273.iQpEcjLWDA@thomas> (raw)
In-Reply-To: <CALBAE1NzutaQ421q173H4B1iXOL3C2tuBhT2RWRP4Cv3cUK8DQ@mail.gmail.com>

08/07/2021 08:32, Jerin Jacob:
> On Thu, Jul 8, 2021 at 11:55 AM Ruifeng Wang <Ruifeng.Wang@arm.com> wrote:
> > From: Jerin Jacob <jerinjacobk@gmail.com>
> > > On Wed, Jul 7, 2021 at 5:57 PM Bruce Richardson
> > > <bruce.richardson@intel.com> wrote:
> > > > On Wed, Jul 07, 2021 at 06:46:33AM +0000, Ruifeng Wang wrote:
> > > > > From: Thomas Monjalon <thomas@monjalon.net>
> > > > > > 07/07/2021 07:48, Ruifeng Wang:
> > > > > > > Introduce a meson option 'use_wfe' to select wait until equal method.
> > > > > > > The default is disable. Traditional polling loop is used.
> > > > > > > When enabled, architecture specific mechanism is relied on to do
> > > > > > > the wait.
> > > > > >
> > > > > > Why do we need an option?
> > > > > > Can it be automatic to enable it when supported?
> > > > > >
> > > > > The problem is inconsistency in performance on different Arm platforms.
> > > We had decided that each platform needs to enable it after some testing.
> > > > >
> > > > Can that not be done via variables in the cross-file for the builds,
> > > > or via automatic detection if it's a native build? Is it likely that
> > > > individual users of DPDK will be knowledgable enough to use this option
> > > correctly?
> > >
> > > +1 to add this in cross-file instead of the top of config option as
> > > scope if is only for arm64 builds.
> >
> > Currently this option is in config/arm/meson.build (flags_common). SoCs can build
> > with this option enabled/disabled. And the ability is available for both native build
> > and cross build as cross build also goes through meson.build.
> > If a SoC needs to enable the option by default, an entry and be added to the SoC flags.
> >
> > The key difference here is whether this option need to be exposed to the top level config.
> 
> In the view of limiting top-level config options and it is specific to
> Arm, I think, it better to
> be a cross file only option.

+1, sorry for the late notice.
I would advocate to take this patch in 21.08-rc2.