Re: [PATCH RFC 07/15] mm/mglru: move refault workingset activation into lru_gen_refault

[Baoquan He]

On 08/04/26 at 03:47am, Kairui Song via B4 Relay wrote:
> From: Kairui Song <kasong@xxxxxxxxxxx>
> 
> Move the folio_set_active() for refaulted workingset folios from
> folio_add_lru() into lru_gen_refault(), where the refault detection
> already happens.  No functional change: the ordering and logic are
> preserved in all cases, and no other paths reach the removed branch.

It doesn't explain or even mention why it doesn't matter to
discarding these two checkings.

!folio_test_unevictable(folio)
!(current->flags & PF_MEMALLOC)
> 
> This is a preparatory cleanup for MGLRU-FG.
> ---
>  mm/folio.c      | 6 +-----
>  mm/workingset.c | 9 ++++-----
>  2 files changed, 5 insertions(+), 10 deletions(-)
> 
> diff --git a/mm/folio.c b/mm/folio.c
> index f90b7f86dbe3..fab00cb02970 100644
> --- a/mm/folio.c
> +++ b/mm/folio.c
> @@ -474,17 +474,13 @@ void folio_add_lru(struct folio *folio)
>  	VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
>  
>  	/*
> -	 * For refaulted workingset folios, set PG_active so they
> -	 * can be added to active generations.
>  	 * For prefaulted file folios, folio_mark_accessed() sets
>  	 * PG_referenced so lru_gen_folio_seq() places them into
>  	 * the second oldest generation.
>  	 */
>  	if (lru_gen_enabled() && !folio_test_unevictable(folio) &&
>  	    lru_gen_in_fault() && !(current->flags & PF_MEMALLOC)) {
> -		if (folio_test_workingset(folio))
> -			folio_set_active(folio);
> -		else if (!folio_test_referenced(folio))
> +		if (!folio_test_referenced(folio) && !folio_test_workingset(folio))
>  			folio_mark_accessed(folio);
>  	}
>  
> diff --git a/mm/workingset.c b/mm/workingset.c
> index 7ac2b88c80ae..5438e9390011 100644
> --- a/mm/workingset.c
> +++ b/mm/workingset.c
> @@ -320,12 +320,11 @@ static void lru_gen_refault(struct folio *folio, void *shadow)
>  	atomic_long_add(delta, &lrugen->refaulted[hist][type][tier]);
>  
>  	if (workingset) {
> -		/*
> -		 * see folio_add_lru(), where folio_set_active() is
> -		 * called for workingset folios
> -		 */
> -		if (lru_gen_in_fault())
> +		/* Send refaulted workingset folios to active generations. */
> +		if (lru_gen_in_fault()) {
> +			folio_set_active(folio);
>  			mod_lruvec_state(lruvec, WORKINGSET_ACTIVATE_BASE + type, delta);
> +		}
>  		folio_set_workingset(folio);
>  		mod_lruvec_state(lruvec, WORKINGSET_RESTORE_BASE + type, delta);
>  	} else
> 
> -- 
> 2.55.0
> 
>