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

[Koen Vandeputte]

On 2018-01-21 13:37, Jonas Gorski wrote:
> 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.
Hi Jonas,

Could you elaborate a bit more on this specific point?
I'm not quite fully understanding your proposal here.

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

>
> Regards
> Jonas