On 2020-11-05 13:57, Linus Walleij wrote:
On Wed, Oct 28, 2020 at 3:51 PM Geert Uytterhoeven
<geert+renesas@xxxxxxxxx> wrote:
On 64-bit platforms, pointer size and alignment are 64-bit, hence two
4-byte holes are present before the pins and gc members of the
pinctrl_gpio_range structure. Get rid of these holes by moving the
pins pointer.
This reduces kernel size of an arm64 Rockchip kernel by ca. 512 bytes.
Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
---
Compile-tested only (arm/multi_v7_defconfig and arm64/defconfig).
Patch applied.
Do you think it'd be worth it to add a check to checkpatch to suggest
to move pointers toward the end of any struct?
For a general rule, I thought that ordering struct members largest-first
was the conventional wisdom, since that way no sensible compiler would
add padding between any members, only at the end?
That said, the trouble with any checkpatch rule is that people will
inevitably try to apply it indiscriminately. With structure layout, that
could often end up hurting readability and/or performance (via cache
effects), while in many cases making no actual difference to the overall
size anyway.
Robin.
