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

[David Hildenbrand (Arm)]

On 4/24/26 09:51, 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@xxxxxxxxxx>
> 
> 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 think there was a lengthy discussion involving Johannes from a previous series.

That should be linked here indeed.

-- 
Cheers,

David