[PATCH] ARM: makefile: add tuning options for Armada 370/XP

[Gregory CLEMENT]

Hi Willy,

On 04/06/2013 09:29 PM, Willy Tarreau wrote:
> Hi,
> 
> A patch from Marvell was merged in GCC 4.8 to add support for their
> PJ4 CPU core used in Armada370 and XP. I noticed a steady 2% network
> performance increase using -mcpu=marvell-pj4 and around 1% when using
> -mtune=xscale instead. I have no idea whether it provides anything to
> the Dove platform and I don't have one to test, so I didn't touch it.
> 
> Now that 4.8 is released, it would be nice to have this option used
> when supported.

Sure it will be very nice! But what happens when the kernel is built
in multiarch?
It seems to me that in this case gcc will tune the code for PJ4 whereas
the kernel built can also be run on a Cortex-A, a Scorpion or a Krait.

Regards,
> 
> Regards,
> Willy
> 
> From b5b34f87e753fbd756f3c23536e731bb1aa6bf7f Mon Sep 17 00:00:00 2001
> From: Willy Tarreau <w at 1wt.eu>
> Date: Sun, 3 Mar 2013 23:26:41 +0100
> Subject: [PATCH] ARM: makefile: add tuning options for Armada 370/XP
> 
> Let's pass -mcpu=marvell-pj4 and fall back to -mtune=xscale for Armada370
> and ArmadaXP. Both settings have shown an improvement over the default
> setting on these chips using gcc-4.7 with and without the Marvell patch
> (typically 2% on network traffic).
> 
> Signed-off-by: Willy Tarreau <w at 1wt.eu>
> ---
>  arch/arm/Makefile | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm/Makefile b/arch/arm/Makefile
> index 15747d9..7dd5418 100644
> --- a/arch/arm/Makefile
> +++ b/arch/arm/Makefile
> @@ -93,6 +93,7 @@ tune-$(CONFIG_CPU_XSC3)		:=$(call cc-option,-mtune=xscale,-mtune=strongarm110) -
>  tune-$(CONFIG_CPU_FEROCEON)	:=$(call cc-option,-mtune=marvell-f,-mtune=xscale)
>  tune-$(CONFIG_CPU_V6)		:=$(call cc-option,-mtune=arm1136j-s,-mtune=strongarm)
>  tune-$(CONFIG_CPU_V6K)		:=$(call cc-option,-mtune=arm1136j-s,-mtune=strongarm)
> +tune-$(CONFIG_MACH_ARMADA_370_XP)	:=$(call cc-option,-mcpu=marvell-pj4,-mtune=xscale)
>  
>  ifeq ($(CONFIG_AEABI),y)
>  CFLAGS_ABI	:=-mabi=aapcs-linux -mno-thumb-interwork
> 


-- 
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com