Re: [PATCH v3 2/2] mm: mglru: promote mapped executable folios after first usage

[Baolin Wang]

On 7/17/26 8:44 PM, Johannes Weiner wrote:
> On Fri, Jul 17, 2026 at 06:05:34PM +0800, 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
> >
> > While we are at it, introduce a new helper to check mapped executable
> > file folios.
> >
> > Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
>
> Both patches contained herein look good:
>
> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>

Thanks for reviewing.

> [ Sorry ;-) Please don't mix refactoring work with functional
>    changes. It's difficult to look through a sequence of diff hunks
>    with more than one review narrative interleaved. ]

Ha, sure. Sorry for mixing in a helper replacement. I'll split it out 
into a separate patch next time. :)