Re: [PATCH next] mm/swap.c: reduce lock contention in lru_cache_add

Alex Shi
2020-11-26T08:09:48Z

在 2020/11/26 下午3:24, Yu Zhao 写道:
> Oh, no, I'm not against your idea. I was saying it doesn't seem
> necessary to sort -- a nested loop would just do the job given
> pagevec is small.
>
> diff --git a/mm/swap.c b/mm/swap.c
> index cb3794e13b48..1d238edc2907 100644
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -996,15 +996,26 @@ static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec)
> */
> void __pagevec_lru_add(struct pagevec *pvec)
> {
> - int i;
> + int i, j;
> struct lruvec *lruvec = NULL;
> unsigned long flags = 0;
>
> for (i = 0; i < pagevec_count(pvec); i++) {
> struct page *page = pvec->pages[i];
>
> + if (!page)
> + continue;
> +
> lruvec = relock_page_lruvec_irqsave(page, lruvec, &flags);
> - __pagevec_lru_add_fn(page, lruvec);
> +
> + for (j = i; j < pagevec_count(pvec); j++) {
> + if (page_to_nid(pvec->pages[j]) != page_to_nid(page) ||
> + page_memcg(pvec->pages[j]) != page_memcg(page))
> + continue;
> +
> + __pagevec_lru_add_fn(pvec->pages[j], lruvec);
> + pvec->pages[j] = NULL;
> + }

Uh, I have to say your method is more better than mine.
And this could be reused for all relock_page_lruvec. I expect this could
speed up lru performance a lot!

> }
> if (lruvec)
> unlock_page_lruvec_irqrestore(lruvec, flags);