On Tue, Jun 18, 2024 at 12:40:23PM -0400, JunChao Sun wrote: > Darrick J. Wong <djwong@xxxxxxxxxx> 于2024年6月18日周二 12:23写道： > > > > On Tue, Jun 18, 2024 at 07:35:04PM +0800, Junchao Sun wrote: > > > By reordering the elements in the xfs_inode structure, we can > > > reduce the padding needed on an x86_64 system by 8 bytes. > > > > > > > Does this result in denser packing of xfs_inode objects in the slab > > > page? > > No. Before applying the patch, the size of xfs_inode is 1800 bytes > with my config, and after applying the patch, the size is 1792 bytes. > This slight reduction does not result in a denser packing of xfs_inode > objects within a single page. The "config dependent" part of this is important though. On my laptop running Debian 6.6.15-amd64, xfs_inode is exactly 1024 bytes, and slab chooses to allocate 32 of them from an order-3 slab. Your config gets you 18 from an order-3 slab, and you'd need to get it down to 1724 (probably 1720 bytes due to alignment) to get 19 from an order-3 slab. I bet you have lockdep or something on.
