Re: [PATCH v2 1/3] mm/mglru: factor out lru_gen_seq_nr_pages()

[Baoquan He]

On 09/11/26 at 06:29pm, Ridong Chen wrote:
> From: Ridong Chen <chenridong@xxxxxxxxxx>
> 
> Both lruvec_evictable_size() and the debugfs lru_gen_seq_show() compute
> the number of pages in a generation the same way: sum lrugen->nr_pages
> over all zones for a given (gen, type) and clamp each term to >= 0.
> 
> Factor that out into lru_gen_seq_nr_pages() so the open-coded zone loop
> lives in one place. No functional change.
> 
> A follow-up patch adds a tracepoint that needs the same per-generation
> page count, and will reuse this helper instead of open-coding it again.
> 
> Assisted-by: Claude:claude-opus-4-8
> Signed-off-by: Ridong Chen <chenridong@xxxxxxxxxx>
> ---
>  mm/vmscan.c | 24 ++++++++++++++++--------
>  1 file changed, 16 insertions(+), 8 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 40d3f1b48a74..2554a6513aa8 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2813,6 +2813,18 @@ static int get_nr_gens(struct lruvec *lruvec, int type)
>  	return lruvec->lrugen.max_seq - lruvec->lrugen.min_seq[type] + 1;
>  }
>  
> +/* the number of pages in a generation, summed over zones and clamped to >= 0 */
      ^
The first letter should be capitalized?

Other than the nit, LGTM,

Reviewed-by: Baoquan He <baoquan.he@xxxxxxxxx>

> +static unsigned long lru_gen_seq_nr_pages(struct lru_gen_folio *lrugen, int gen, int type)
> +{
> +	int zone;
> +	unsigned long size = 0;
> +
> +	for (zone = 0; zone < MAX_NR_ZONES; zone++)
> +		size += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L);
> +
> +	return size;
> +}
> +
>  static bool __maybe_unused seq_is_valid(struct lruvec *lruvec)
>  {
>  	int type;
> @@ -4239,7 +4251,7 @@ static void set_initial_priority(struct pglist_data *pgdat, struct scan_control
>  
>  static unsigned long lruvec_evictable_size(struct lruvec *lruvec, int swappiness)
>  {
> -	int gen, type, zone;
> +	int gen, type;
>  	unsigned long seq, total = 0;
>  	struct lru_gen_folio *lrugen = &lruvec->lrugen;
>  	DEFINE_MAX_SEQ(lruvec);
> @@ -4248,8 +4260,7 @@ static unsigned long lruvec_evictable_size(struct lruvec *lruvec, int swappiness
>  	for_each_evictable_type(type, swappiness) {
>  		for (seq = min_seq[type]; seq <= max_seq; seq++) {
>  			gen = lru_gen_from_seq(seq);
> -			for (zone = 0; zone < MAX_NR_ZONES; zone++)
> -				total += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L);
> +			total += lru_gen_seq_nr_pages(lrugen, gen, type);
>  		}
>  	}
>  
> @@ -5738,19 +5749,16 @@ static int lru_gen_seq_show(struct seq_file *m, void *v)
>  		seq = 0;
>  
>  	for (; seq <= max_seq; seq++) {
> -		int type, zone;
> +		int type;
>  		int gen = lru_gen_from_seq(seq);
>  		unsigned long birth = READ_ONCE(lruvec->lrugen.timestamps[gen]);
>  
>  		seq_printf(m, " %10lu %10u", seq, jiffies_to_msecs(jiffies - birth));
>  
>  		for (type = 0; type < ANON_AND_FILE; type++) {
> -			unsigned long size = 0;
> +			unsigned long size = lru_gen_seq_nr_pages(lrugen, gen, type);
>  			char mark = full && seq < min_seq[type] ? 'x' : ' ';
>  
> -			for (zone = 0; zone < MAX_NR_ZONES; zone++)
> -				size += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L);
> -
>  			seq_printf(m, " %10lu%c", size, mark);
>  		}
>  
> -- 
> 2.34.1
>