From: Jan Viktorin <viktorin@rehivetech.com>
To: "Kulasek, TomaszX" <tomaszx.kulasek@intel.com>
Cc: Thomas Monjalon <thomas.monjalon@6wind.com>,
Jerin Jacob <jerin.jacob@caviumnetworks.com>,
"dev@dpdk.org" <dev@dpdk.org>,
"jianbo.liu@linaro.org" <jianbo.liu@linaro.org>
Subject: Re: [dpdk-dev] [PATCH v5] examples/l3fwd: em path performance fix
Date: Fri, 18 Mar 2016 13:50:36 +0100 [thread overview]
Message-ID: <20160318135036.631fa60a@pcviktorin.fit.vutbr.cz> (raw)
In-Reply-To: <3042915272161B4EB253DA4D77EB373A14E6C71E@IRSMSX102.ger.corp.intel.com>
On Fri, 18 Mar 2016 12:45:03 +0000
"Kulasek, TomaszX" <tomaszx.kulasek@intel.com> wrote:
> > -----Original Message-----
> > From: Jan Viktorin [mailto:viktorin@rehivetech.com]
> > Sent: Friday, March 18, 2016 12:57
> > To: Thomas Monjalon <thomas.monjalon@6wind.com>
> > Cc: Jerin Jacob <jerin.jacob@caviumnetworks.com>; Kulasek, TomaszX
> > <tomaszx.kulasek@intel.com>; dev@dpdk.org; jianbo.liu@linaro.org
> > Subject: Re: [dpdk-dev] [PATCH v5] examples/l3fwd: em path performance fix
> >
> > Hello Thomas, Jerin, Tomasz, all...
> >
> > On Fri, 18 Mar 2016 12:00:24 +0100
> > Thomas Monjalon <thomas.monjalon@6wind.com> wrote:
> >
> > > 2016-03-18 16:22, Jerin Jacob:
> > > > On Fri, Mar 18, 2016 at 11:04:49AM +0100, Thomas Monjalon wrote:
> > > > > 2016-03-18 10:52, Tomasz Kulasek:
> > > > > > +#if !defined(NO_HASH_MULTI_LOOKUP) && defined(__ARM_NEON)
> > > > >
> > > > > I think we should use CONFIG_RTE_ARCH_ARM_NEON here.
> > > > > Any ARM maintainer to confirm?
> > > >
> > > > __ARM_NEON should work existing GCC, but it is better to use
> > > > RTE_MACHINE_CPUFLAG_NEON as -it has been generated by probing the
> > > > compiler capabilities.
> > > > -it's future-proof solution to support clang or other gcc versions
> > > > in future
> > >
> > > I agree to use RTE_MACHINE_CPUFLAG_NEON.
> > >
> > > I just don't understand why CONFIG_RTE_ARCH_ARM_NEON has been
> > introduced.
> > > It seems to be used to disable NEON on ARMv7:
> >
> > This is true. You should be able to disable the NEON-specific code if it
> > is unwanted. Eg., the memcpy operations are not always faster with NEON.
> > But...
> >
> > $ git grep ARM_NEON
> > ...
> > lib/librte_eal/common/include/arch/arm/rte_memcpy_32.h:45:#ifdef
> > __ARM_NEON_FP
> > lib/librte_eal/common/include/arch/arm/rte_memcpy_32.h:328:#endif /*
> > __ARM_NEON_FP */ ...
> >
> > From this point of view, this is wrong and should be fixed to check a
> > different constant.
> >
> > > ifeq ($(CONFIG_RTE_ARCH_ARM_NEON),y)
> > > MACHINE_CFLAGS += -mfpu=neon
> > > endif
> >
> > However, there is another possible way of understanding these options.
> > We can (well, unlikely and I am about to say 'never') have an ARM
> > processor without NEON. This cannot be detected by gcc as it does not know
> > the target processor... So from my point of view:
> >
> > * CONFIG_RTE_ARCH_ARM_NEON says "my CPU does (not) support NEON" or "I
> > want to enable/disable NEON" while
> > * RTE_MACHINE_CPUFLAG_NEON says, the _compiler_ supports NEON
> >
> > I'll send a patch trying to solve this.
> >
> > Regards
> > Jan
>
> Hi
>
> As I understand with your last patch it's safe and preferred to use RTE_MACHINE_CPUFLAG_NEON for ARM Neon detection? If so, I can include this modification for whole l3fwd in v6 of this patch.
Yes, I'd prefer this approach as well.
Jan
>
> Tomasz.
--
Jan Viktorin E-mail: Viktorin@RehiveTech.com
System Architect Web: www.RehiveTech.com
RehiveTech
Brno, Czech Republic
next prev parent reply other threads:[~2016-03-18 12:50 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-03 17:23 [dpdk-dev] [PATCH] " Tomasz Kulasek
2016-03-07 6:19 ` Xu, Qian Q
2016-03-08 12:58 ` [dpdk-dev] [PATCH v2] " Tomasz Kulasek
2016-03-11 11:14 ` Thomas Monjalon
2016-03-11 12:28 ` Kulasek, TomaszX
2016-03-11 12:10 ` [dpdk-dev] [PATCH v3] " Tomasz Kulasek
2016-03-11 16:23 ` Thomas Monjalon
2016-03-11 17:48 ` Kulasek, TomaszX
2016-03-15 14:31 ` Kulasek, TomaszX
2016-03-15 14:49 ` Thomas Monjalon
2016-03-15 16:06 ` Kulasek, TomaszX
2016-03-15 19:42 ` [dpdk-dev] Odp.: " Czekaj, Maciej
2016-03-18 9:36 ` [dpdk-dev] [PATCH v4] " Tomasz Kulasek
2016-03-18 9:43 ` Kulasek, TomaszX
2016-03-18 9:52 ` [dpdk-dev] [PATCH v5] " Tomasz Kulasek
2016-03-18 10:04 ` Thomas Monjalon
2016-03-18 10:52 ` Jerin Jacob
2016-03-18 11:00 ` Thomas Monjalon
2016-03-18 11:16 ` [dpdk-dev] [PATCH] examples/l3fwd: prefer probed NEON flag to ARM gcc flag Thomas Monjalon
2016-03-18 11:20 ` [dpdk-dev] [PATCH v2] " Thomas Monjalon
2016-03-18 11:56 ` [dpdk-dev] [PATCH v5] examples/l3fwd: em path performance fix Jan Viktorin
2016-03-18 12:45 ` Kulasek, TomaszX
2016-03-18 12:50 ` Jan Viktorin [this message]
2016-03-18 13:31 ` [dpdk-dev] [PATCH v6] " Tomasz Kulasek
2016-03-21 11:57 ` Thomas Monjalon
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