| Message ID | 6b868520dac20434296b6282496d3234fae01115.1676631473.git.christophe.jaillet@wanadoo.fr (mailing list archive) |
|---|---|
| State | RFC, archived |
| Headers | show |
| Series | ACPI: video: Reorder fields in 'struct acpi_video_device' | expand |
diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c index 97b711e57bff..1118dd7dbf6c 100644 --- a/drivers/acpi/acpi_video.c +++ b/drivers/acpi/acpi_video.c @@ -202,11 +202,11 @@ struct acpi_video_device_cap { struct acpi_video_device { unsigned long device_id; + struct list_head entry; struct acpi_video_device_flags flags; struct acpi_video_device_cap cap; - struct list_head entry; - struct delayed_work switch_brightness_work; int switch_brightness_event; + struct delayed_work switch_brightness_work; struct acpi_video_bus *video; struct acpi_device *dev; struct acpi_video_device_brightness *brightness;
Group some variables based on their sizes to reduce hole and avoid padding. On x86_64, this shrinks the size of 'struct acpi_video_device' from 264 to 256 bytes. This size is much better when the struct is kmalloc()'ed. Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr> --- Using pahole Before: ====== struct acpi_video_device { long unsigned int device_id; /* 0 8 */ struct acpi_video_device_flags flags; /* 8 1 */ struct acpi_video_device_cap cap; /* 9 1 */ /* XXX 6 bytes hole, try to pack */ struct list_head entry; /* 16 16 */ struct delayed_work switch_brightness_work; /* 32 184 */ /* XXX last struct has 4 bytes of padding */ /* --- cacheline 3 boundary (192 bytes) was 24 bytes ago --- */ int switch_brightness_event; /* 216 4 */ /* XXX 4 bytes hole, try to pack */ struct acpi_video_bus * video; /* 224 8 */ struct acpi_device * dev; /* 232 8 */ struct acpi_video_device_brightness * brightness; /* 240 8 */ struct backlight_device * backlight; /* 248 8 */ /* --- cacheline 4 boundary (256 bytes) --- */ struct thermal_cooling_device * cooling_dev; /* 256 8 */ /* size: 264, cachelines: 5, members: 11 */ /* sum members: 254, holes: 2, sum holes: 10 */ /* paddings: 1, sum paddings: 4 */ /* last cacheline: 8 bytes */ }; After: ===== struct acpi_video_device { long unsigned int device_id; /* 0 8 */ struct list_head entry; /* 8 16 */ struct acpi_video_device_flags flags; /* 24 1 */ struct acpi_video_device_cap cap; /* 25 1 */ /* XXX 2 bytes hole, try to pack */ int switch_brightness_event; /* 28 4 */ struct delayed_work switch_brightness_work; /* 32 184 */ /* XXX last struct has 4 bytes of padding */ /* --- cacheline 3 boundary (192 bytes) was 24 bytes ago --- */ struct acpi_video_bus * video; /* 216 8 */ struct acpi_device * dev; /* 224 8 */ struct acpi_video_device_brightness * brightness; /* 232 8 */ struct backlight_device * backlight; /* 240 8 */ struct thermal_cooling_device * cooling_dev; /* 248 8 */ /* size: 256, cachelines: 4, members: 11 */ /* sum members: 254, holes: 1, sum holes: 2 */ /* paddings: 1, sum paddings: 4 */ }; --- drivers/acpi/acpi_video.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)