[LEDE-DEV] [PATCH] config: add option to select kernel compile optimization type

[Jonas Gorski]

Hi,

On 18 January 2018 at 10:50, Koen Vandeputte
<koen.vandeputte at ncentric.com> wrote:
> A lot of targets have more than sufficient space to allow
> building the kernel for speed iso size.
>
> Export this performance option to the main config:
>
> - Making it easy accessable for users
> - Discarding the need to adjust it in the kernel config each time
> when building from scratch and only using "make oldconfig"
>
> Compiling for size is still the default.

This would be a "regression" for layerscape, as this target sets
CC_OPTIMIZE_FOR_PERFORMANCE to y.

>
> Purely informational:
>
> On my cns3xxx board, kernel size increases by ~100kB
> but boot time decreased by ~8%.
>
> Signed-off-by: Koen Vandeputte <koen.vandeputte at ncentric.com>
> ---
>  config/Config-kernel.in | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
>
> diff --git a/config/Config-kernel.in b/config/Config-kernel.in
> index fa06b5044219..b98c5dd04591 100644
> --- a/config/Config-kernel.in
> +++ b/config/Config-kernel.in
> @@ -194,6 +194,22 @@ config KERNEL_DEBUG_GPIO
>         bool "Compile the kernel with gpio debugging"
>         select KERNEL_DEBUG_KERNEL
>
> +config KERNEL_CC_OPTIMIZE_FOR_PERFORMANCE
> +        bool
> +        default y if COMPILE_KERNEL_FOR_SPEED
> +        default n
> +
> +config KERNEL_CC_OPTIMIZE_FOR_SIZE
> +        bool
> +        default n if COMPILE_KERNEL_FOR_SPEED
> +        default y
> +
> +config COMPILE_KERNEL_FOR_SPEED
> +        bool "Optimize the kernel for speed instead of size"
> +        default n
> +        help
> +          This will compile your kernel for maximum speed (-O2) instead of smaller size (-Os)

The kernel uses a choice here, so I think it would be better to just
copy that. One less config option as well.

Also the options should be removed from the kernel configs then.


Regards
Jonas