On Fri, Feb 02, 2024 at 05:34:07PM +0800, JonasZhou-oc wrote: > In the struct address_space, there is a 32-byte gap between i_mmap > and i_mmap_rwsem. Due to the alignment of struct address_space > variables to 8 bytes, in certain situations, i_mmap and > i_mmap_rwsem may end up in the same CACHE line. > > While running Unixbench/execl, we observe high false sharing issues > when accessing i_mmap against i_mmap_rwsem. We move i_mmap_rwsem > after i_private_list, ensuring a 64-byte gap between i_mmap and > i_mmap_rwsem. I'm confused. i_mmap_rwsem protects i_mmap. Usually you want the lock and the thing it's protecting in the same cacheline. Why is that not the case here?
