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Subject: Re: [PATCH next] mm/swap.c: reduce lock contention in lru_cache_add
To:     Yu Zhao <yuzhao@google.com>
Cc:     Konstantin Khlebnikov <koct9i@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Hugh Dickins <hughd@google.com>,
        Michal Hocko <mhocko@suse.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
References: <1605860847-47445-1-git-send-email-alex.shi@linux.alibaba.com>
 <20201126045234.GA1014081@google.com>
 <ed19e3f7-33cb-20ae-537e-a7ada2036895@linux.alibaba.com>
 <20201126072402.GA1047005@google.com>
From:   Alex Shi <alex.shi@linux.alibaba.com>
Message-ID: <0e14f1dc-31bb-5965-4711-9e59c51ee36d@linux.alibaba.com>
Date:   Thu, 26 Nov 2020 16:09:29 +0800
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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);