On Oct 26, 2020, at 9:18 AM, Matthew Wilcox (Oracle) [off-list ref] wrote:

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

Looks good to me.

Reviewed-by: William Kucharski <redacted>