We actually use nrexceptional for very little these days. It's a minor pain to keep in sync with nrpages, but the pain becomes much bigger with the THP patches because we don't know how many indices a shadow entry occupies. It's easier to just remove it than keep it accurate. Also, we save 8 bytes per inode which is nothing to sneeze at; on my laptop, it would improve shmem_inode_cache from 22 to 23 objects per 16kB, and inode_cache from 26 to 27 objects. Combined, that saves a megabyte of memory from a combined usage of 25MB for both caches. Unfortunately, ext4 doesn't cross a magic boundary, so it doesn't save any memory for ext4. Matthew Wilcox (Oracle) (4): mm: Introduce and use mapping_empty mm: Stop accounting shadow entries dax: Account DAX entries as nrpages mm: Remove nrexceptional from inode fs/block_dev.c | 2 +- fs/dax.c | 8 ++++---- fs/gfs2/glock.c | 3 +-- fs/inode.c | 2 +- include/linux/fs.h | 2 -- include/linux/pagemap.h | 5 +++++ mm/filemap.c | 16 ---------------- mm/swap_state.c | 4 ---- mm/truncate.c | 19 +++---------------- mm/workingset.c | 1 - 10 files changed, 15 insertions(+), 47 deletions(-) -- 2.28.0
