Citeren Jonas Gorski <jonas.gor...@gmail.com>:

Hi,

On 18 January 2018 at 10:50, Koen Vandeputte
<koen.vandepu...@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.vandepu...@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.

One thing that wonders me, couldn't the option CONFIG_TARGET_OPTIONS=y and CONFIG_TARGET_OPTIMIZATION that is already available be used for this as well? So far I have used this to set the optimization used, which seems to do the job just fine (for the whole target, not just the kernel).


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