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Date: Mon, 21 Mar 2016 15:01:58 +0100
From: Jan Viktorin <viktorin@rehivetech.com>
To: Thomas Monjalon <thomas.monjalon@6wind.com>
Cc: Jianbo Liu <jianbo.liu@linaro.org>, dev@dpdk.org, Jerin Jacob
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Subject: Re: [dpdk-dev] [PATCH v3 4/4] eal/arm: introduce
 CONFIG_RTE_ARCH_ARM_NEON_MEMCPY
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On Mon, 21 Mar 2016 06:24:37 -0700 (PDT)
Thomas Monjalon <thomas.monjalon@6wind.com> wrote:

> 2016-03-21 13:21, Jan Viktorin:
> > On Mon, 21 Mar 2016 13:42:31 +0800
> > Jianbo Liu <jianbo.liu@linaro.org> wrote:
> >   
> > > On 20 March 2016 at 03:58, Jan Viktorin <viktorin@rehivetech.com> wrote:  
> > > > The flag is used to enable memcpy optimizations in EAL. As it is not always
> > > > the performance benefit, the flag allows to disable it.
> > > >
> > > > Signed-off-by: Jan Viktorin <viktorin@rehivetech.com>
> > > > ---
> > > >  config/defconfig_arm-armv7a-linuxapp-gcc               | 1 +
> > > >  lib/librte_eal/common/include/arch/arm/rte_memcpy_32.h | 8 ++++++--
> > > >  2 files changed, 7 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/config/defconfig_arm-armv7a-linuxapp-gcc b/config/defconfig_arm-armv7a-linuxapp-gcc
> > > > index 96c3343..2c60c2c 100644
> > > > --- a/config/defconfig_arm-armv7a-linuxapp-gcc
> > > > +++ b/config/defconfig_arm-armv7a-linuxapp-gcc
> > > > @@ -36,6 +36,7 @@ CONFIG_RTE_ARCH="arm"
> > > >  CONFIG_RTE_ARCH_ARM=y
> > > >  CONFIG_RTE_ARCH_ARMv7=y
> > > >  CONFIG_RTE_ARCH_ARM_TUNE="cortex-a9"
> > > > +CONFIG_RTE_ARCH_ARM_NEON_MEMCPY=y
> > > >    
> > > If it's not always benefit, why not disable here since it is common
> > > armv7a config, and enable in your or other user's own config file?  
> > 
> > Jianbo, you are right. In that case, I'd just turn it off by default.
> > And when there is a new platform-specific defconfig, it can enable it.
> > 
> > Anyway, I am thinking of adding some comment into the rte_memcpy_32.h
> > file describing the potential of the NEON code. What about:
> > 
> > /* Enable in your defconfig to accelerate memcpy operations. Consider
> >    enabling this for Cortex-A15. For Cortex-A7 and Cortex-A9, It might
> >    accelerate short data copies (< 64 B). */
> > 
> > Thomas, do you consider this enough?  
> 
> Yes it is perfect.
> Why not put it in defconfig_arm-armv7a-linuxapp-gcc?

So, for now, I leave the patch as is and just add the comment.

Jan