Re: [PATCH v2 2/2] mm: mglru: promote mapped executable folios after first usage

["David Hildenbrand (Arm)" <david@kernel.org>]

On 7/16/26 12:46, Baolin Wang wrote:
> Classical LRU protects mapped executable file folios through commit
> 8cab4754d24a0 ("vmscan: make mapped executable pages the first class
> citizen") and commit c909e99364c8 ("vmscan: activate executable pages
> after first usage"), giving executable code a better chance to stay in
> memory, avoiding IO thrashing and improving workload performance.
> 
> However, MGLRU's protection of mapped executable file folios is less
> reliable. Although shrink_folio_list() checks references, the access flag
> of mapped executable file folios may have already been checked and
> cleared by lru_gen_look_around() or walk_mm(). Additionally,
> folio_update_gen() or lru_gen_set_refs() only sets the 'PG_referenced'
> flag for mapped executable file folios, which causes shrink_folio_list()
> to ignore the first usage of these mapped executable file folios and
> reclaim them easily.
> 
> Follow the classical LRU's logic, promoting mapped executable file folios
> after their first usage in folio_update_gen() and lru_gen_set_refs(),
> giving executable code a better chance to stay in memory.
> 
> On my 32-core Arm machine, with the memcg limit set to 2G, running
> 'make -j32' to build kernel showed some improvement in sys time.
> 
> base			patched
> 9248.543s		7861.579s
> 
> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
> ---
>  include/linux/mm_inline.h |  6 ++++++
>  mm/vmscan.c               | 41 ++++++++++++++++++++++++---------------
>  2 files changed, 31 insertions(+), 16 deletions(-)
> 
> diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
> index b5c4dc0f3fe3..30fdf1056312 100644
> --- a/include/linux/mm_inline.h
> +++ b/include/linux/mm_inline.h
> @@ -30,6 +30,12 @@ static inline int folio_is_file_lru(const struct folio *folio)
>  	return !folio_test_swapbacked(folio);
>  }
>  
> +static inline bool folio_is_exec_file(const struct folio *folio,
> +		const vma_flags_t *vma_flags)
> +{
> +	return vma_flags_test(vma_flags, VMA_EXEC_BIT) && folio_is_file_lru(folio);
> +}

I don't quite like a generic folio_is* helper to consume vma flags. Whether it
is executable depends on the VMA. When called from a non-exec VMA it would just
give a wrong answer.

Not sure if something like "is_executable_file_folio()"/"is_exec_file_folio"
would be better, to distinguish from the actualy folio_is* helpers that are
independent of context.

Also, can this helper just go to vmscan.c?

-- 
Cheers,

David