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

Minchan Kim
2026-04-24T19:26:19Z

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.