Re: [PATCH v1 2/3] mm: process_mrelease: skip LRU movement for exclusive file folios

[Minchan Kim <minchan@kernel.org>]

On Fri, Apr 24, 2026 at 09:51:22AM +0200, Michal Hocko wrote:
> On Tue 21-04-26 16:02:38, Minchan Kim wrote:
> > For the process_mrelease reclaim, skip LRU handling for exclusive
> > file-backed folios since they will be freed soon so pointless
> > to move around in the LRU.
> > 
> > This avoids costly LRU movement which accounts for a significant portion
> > of the time during unmap_page_range.
> > 
> > -   91.31%     0.00%  mmap_exit_test   [kernel.kallsyms]  [.] exit_mm
> >      exit_mm
> >      __mmput
> >      exit_mmap
> >      unmap_vmas
> >    - unmap_page_range
> >       - 55.75% folio_mark_accessed
> >          + 48.79% __folio_batch_add_and_move
> >            4.23% workingset_activation
> >       + 12.94% folio_remove_rmap_ptes
> >       + 9.86% page_table_check_clear
> >       + 3.34% tlb_flush_mmu
> >         1.06% __page_table_check_pte_clear
> > 
> > Signed-off-by: Minchan Kim <minchan@kernel.org>
> 
> As pointed out in the previous version of the patch. I really dislike
> this to be mrelease or OOM specific. Behavior. You do not explain why
> this needs to be this way, except for the performance reasons. My main
> question is still unanswered (and NAK before this is sorted out). Why
> this cannot be applied in general for _any_ exiting task. As you argue
> the memory will just likely go away so why to bother?

I revised the description to explain why I wanted to go with only
specific, not in general.

https://lore.kernel.org/linux-mm/aevBRh08X4UTMUj9@google.com/