| Message ID | 9accb4ebd1247e2f2acc77dd053f67e60bf8d283.1687079502.git.christophe.jaillet@wanadoo.fr (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | HID: Reorder fields in 'struct hid_input' | expand |
On Sun, 18 Jun 2023, 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 hid_input' > from 72 to 64 bytes. > > It saves a few bytes of memory and is more cache-line friendly. Applied, thanks.
diff --git a/include/linux/hid.h b/include/linux/hid.h index 5be5e671c263..d29c5de96a40 100644 --- a/include/linux/hid.h +++ b/include/linux/hid.h @@ -555,9 +555,9 @@ struct hid_input { struct hid_report *report; struct input_dev *input; const char *name; - bool registered; struct list_head reports; /* the list of reports */ unsigned int application; /* application usage for this input */ + bool registered; }; enum hid_type {
Group some variables based on their sizes to reduce hole and avoid padding. On x86_64, this shrinks the size of 'struct hid_input' from 72 to 64 bytes. It saves a few bytes of memory and is more cache-line friendly. Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr> --- Using pahole Before: ====== struct hid_input { struct list_head list; /* 0 16 */ struct hid_report * report; /* 16 8 */ struct input_dev * input; /* 24 8 */ const char * name; /* 32 8 */ bool registered; /* 40 1 */ /* XXX 7 bytes hole, try to pack */ struct list_head reports; /* 48 16 */ /* --- cacheline 1 boundary (64 bytes) --- */ unsigned int application; /* 64 4 */ /* size: 72, cachelines: 2, members: 7 */ /* sum members: 61, holes: 1, sum holes: 7 */ /* padding: 4 */ /* last cacheline: 8 bytes */ }; After: ===== struct hid_input { struct list_head list; /* 0 16 */ struct hid_report * report; /* 16 8 */ struct input_dev * input; /* 24 8 */ const char * name; /* 32 8 */ struct list_head reports; /* 40 16 */ unsigned int application; /* 56 4 */ bool registered; /* 60 1 */ /* size: 64, cachelines: 1, members: 7 */ /* padding: 3 */ }; --- include/linux/hid.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)