| Message ID | 20240618113505.476072-2-sunjunchao2870@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [1/2] xfs: reorder xfs_inode structure elements to remove unneeded padding. | expand |
On Tue, Jun 18, 2024 at 07:35:05PM GMT, Junchao Sun wrote: > By reordering the elements in the struct file structure, we can > reduce the padding needed on an x86_64 system by 8 bytes. > > Signed-off-by: Junchao Sun <sunjunchao2870@gmail.com> > --- > include/linux/fs.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/linux/fs.h b/include/linux/fs.h > index 0283cf366c2a..9235b7a960d3 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -999,10 +999,10 @@ struct file { > */ > spinlock_t f_lock; > fmode_t f_mode; > + unsigned int f_flags; Iiuc, then this will push f_pos_lock into a new cache line whereas it's explicitly optimized so that f_lock, f_mode, and f_pos_lock are all in the same cache line. You could play around with moving the union to the end of struct file.
diff --git a/include/linux/fs.h b/include/linux/fs.h index 0283cf366c2a..9235b7a960d3 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -999,10 +999,10 @@ struct file { */ spinlock_t f_lock; fmode_t f_mode; + unsigned int f_flags; atomic_long_t f_count; struct mutex f_pos_lock; loff_t f_pos; - unsigned int f_flags; struct fown_struct f_owner; const struct cred *f_cred; struct file_ra_state f_ra;
By reordering the elements in the struct file structure, we can reduce the padding needed on an x86_64 system by 8 bytes. Signed-off-by: Junchao Sun <sunjunchao2870@gmail.com> --- include/linux/fs.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)