Re: [PATCH v5 07/14] fs: remove nr_thps from struct address_space

[Nico Pache]

On 4/29/26 9:35 AM, Zi Yan wrote:
> filemap_nr_thps*() are removed, the related field, address_space->nr_thps,
> is no longer needed. Remove it. This shrinks struct address_space by 8
> bytes on 64-bit systems which may increase the number of inodes we can
> cache.

We've had performance impacts in the past by changing the alignment of 
certain structs. This is a rather critical one. Ill keep an eye out for 
any performance differences noted by our PerfQE team surrounding this 
feature.

LGTM!

Reviewed-by: Nico Pache <npache@xxxxxxxxxx>

> Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
> Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@xxxxxxxxxx>
> Acked-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>
> Reviewed-by: Lance Yang <lance.yang@xxxxxxxxx>
> Reviewed-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> ---
>   fs/inode.c         | 3 ---
>   include/linux/fs.h | 5 -----
>   2 files changed, 8 deletions(-)
>
> diff --git a/fs/inode.c b/fs/inode.c
> index 6a3cbc7dcd28c..d8a6d6266c3c3 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -279,9 +279,6 @@ int inode_init_always_gfp(struct super_block *sb, struct inode *inode, gfp_t gfp
>   	mapping->flags = 0;
>   	mapping->wb_err = 0;
>   	atomic_set(&mapping->i_mmap_writable, 0);
> -#ifdef CONFIG_READ_ONLY_THP_FOR_FS
> -	atomic_set(&mapping->nr_thps, 0);
> -#endif
>   	mapping_set_gfp_mask(mapping, GFP_HIGHUSER_MOVABLE);
>   	mapping->writeback_index = 0;
>   	init_rwsem(&mapping->invalidate_lock);
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 11559c513dfbb..bb9cc4f7207c1 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -460,7 +460,6 @@ struct mapping_metadata_bhs {
>    *   memory mappings.
>    * @gfp_mask: Memory allocation flags to use for allocating pages.
>    * @i_mmap_writable: Number of VM_SHARED, VM_MAYWRITE mappings.
> - * @nr_thps: Number of THPs in the pagecache (non-shmem only).
>    * @i_mmap: Tree of private and shared mappings.
>    * @i_mmap_rwsem: Protects @i_mmap and @i_mmap_writable.
>    * @nrpages: Number of page entries, protected by the i_pages lock.
> @@ -476,10 +475,6 @@ struct address_space {
>   	struct rw_semaphore	invalidate_lock;
>   	gfp_t			gfp_mask;
>   	atomic_t		i_mmap_writable;
> -#ifdef CONFIG_READ_ONLY_THP_FOR_FS
> -	/* number of thp, only for non-shmem files */
> -	atomic_t		nr_thps;
> -#endif
>   	struct rb_root_cached	i_mmap;
>   	unsigned long		nrpages;
>   	pgoff_t			writeback_index;