Re: [PATCH v2 0/4] Remove nrexceptional tracking

[William Kucharski <william.kucharski@oracle.com>]

> On Oct 26, 2020, at 9:18 AM, Matthew Wilcox (Oracle) <willy@infradead.org> 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 <william.kucharski@oracle.com>
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