| Message ID | f5745aeab896f8d4622ff4c3cd0475d9be6bafd8.1687121400.git.christophe.jaillet@wanadoo.fr (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Headers | show |
| Series | video/hdmi: Reorder fields in 'struct hdmi_avi_infoframe' | expand |
On 6/18/23 22:52, Christophe JAILLET wrote: > 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@wanadoo.fr> applied. Thanks! Helge > --- > 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;
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;
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@wanadoo.fr> --- 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(-)