Group some variables based on their sizes to reduce hole and avoid padding. On x86_64, this shrinks the size of 'struct hdmi_avi_infoframe' from 68 to 60 bytes. It saves a few bytes of memory and is more cache-line friendly. This also reduces the union hdmi_infoframe the same way. Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx> --- Using pahole Before: ====== struct hdmi_avi_infoframe { enum hdmi_infoframe_type type; /* 0 4 */ unsigned char version; /* 4 1 */ unsigned char length; /* 5 1 */ /* XXX 2 bytes hole, try to pack */ enum hdmi_colorspace colorspace; /* 8 4 */ enum hdmi_scan_mode scan_mode; /* 12 4 */ enum hdmi_colorimetry colorimetry; /* 16 4 */ enum hdmi_picture_aspect picture_aspect; /* 20 4 */ enum hdmi_active_aspect active_aspect; /* 24 4 */ bool itc; /* 28 1 */ /* XXX 3 bytes hole, try to pack */ enum hdmi_extended_colorimetry extended_colorimetry; /* 32 4 */ enum hdmi_quantization_range quantization_range; /* 36 4 */ enum hdmi_nups nups; /* 40 4 */ unsigned char video_code; /* 44 1 */ /* XXX 3 bytes hole, try to pack */ enum hdmi_ycc_quantization_range ycc_quantization_range; /* 48 4 */ enum hdmi_content_type content_type; /* 52 4 */ unsigned char pixel_repeat; /* 56 1 */ /* XXX 1 byte hole, try to pack */ short unsigned int top_bar; /* 58 2 */ short unsigned int bottom_bar; /* 60 2 */ short unsigned int left_bar; /* 62 2 */ /* --- cacheline 1 boundary (64 bytes) --- */ short unsigned int right_bar; /* 64 2 */ /* size: 68, cachelines: 2, members: 20 */ /* sum members: 57, holes: 4, sum holes: 9 */ /* padding: 2 */ /* last cacheline: 4 bytes */ }; After: ===== struct hdmi_avi_infoframe { enum hdmi_infoframe_type type; /* 0 4 */ unsigned char version; /* 4 1 */ unsigned char length; /* 5 1 */ bool itc; /* 6 1 */ unsigned char pixel_repeat; /* 7 1 */ enum hdmi_colorspace colorspace; /* 8 4 */ enum hdmi_scan_mode scan_mode; /* 12 4 */ enum hdmi_colorimetry colorimetry; /* 16 4 */ enum hdmi_picture_aspect picture_aspect; /* 20 4 */ enum hdmi_active_aspect active_aspect; /* 24 4 */ enum hdmi_extended_colorimetry extended_colorimetry; /* 28 4 */ enum hdmi_quantization_range quantization_range; /* 32 4 */ enum hdmi_nups nups; /* 36 4 */ unsigned char video_code; /* 40 1 */ /* XXX 3 bytes hole, try to pack */ enum hdmi_ycc_quantization_range ycc_quantization_range; /* 44 4 */ enum hdmi_content_type content_type; /* 48 4 */ short unsigned int top_bar; /* 52 2 */ short unsigned int bottom_bar; /* 54 2 */ short unsigned int left_bar; /* 56 2 */ short unsigned int right_bar; /* 58 2 */ /* size: 60, cachelines: 1, members: 20 */ /* sum members: 57, holes: 1, sum holes: 3 */ /* last cacheline: 60 bytes */ }; --- include/linux/hdmi.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/linux/hdmi.h b/include/linux/hdmi.h index 2f4dcc8d060e..3bb87bf6bc65 100644 --- a/include/linux/hdmi.h +++ b/include/linux/hdmi.h @@ -170,19 +170,19 @@ struct hdmi_avi_infoframe { enum hdmi_infoframe_type type; unsigned char version; unsigned char length; + bool itc; + unsigned char pixel_repeat; enum hdmi_colorspace colorspace; enum hdmi_scan_mode scan_mode; enum hdmi_colorimetry colorimetry; enum hdmi_picture_aspect picture_aspect; enum hdmi_active_aspect active_aspect; - bool itc; enum hdmi_extended_colorimetry extended_colorimetry; enum hdmi_quantization_range quantization_range; enum hdmi_nups nups; unsigned char video_code; enum hdmi_ycc_quantization_range ycc_quantization_range; enum hdmi_content_type content_type; - unsigned char pixel_repeat; unsigned short top_bar; unsigned short bottom_bar; unsigned short left_bar; -- 2.34.1