linux-kernel - Re: [PATCH v18 15/32] mm/lru: move lock into lru_note

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Date:   Mon, 21 Sep 2020 14:36:52 -0700 (PDT)
From:   Hugh Dickins <hughd@...gle.com>
To:     Alex Shi <alex.shi@...ux.alibaba.com>
cc:     akpm@...ux-foundation.org, mgorman@...hsingularity.net,
        tj@...nel.org, hughd@...gle.com, khlebnikov@...dex-team.ru,
        daniel.m.jordan@...cle.com, willy@...radead.org,
        hannes@...xchg.org, lkp@...el.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
        shakeelb@...gle.com, iamjoonsoo.kim@....com,
        richard.weiyang@...il.com, kirill@...temov.name,
        alexander.duyck@...il.com, rong.a.chen@...el.com, mhocko@...e.com,
        vdavydov.dev@...il.com, shy828301@...il.com
Subject: Re: [PATCH v18 15/32] mm/lru: move lock into lru_note_cost

On Mon, 24 Aug 2020, Alex Shi wrote:

> We have to move lru_lock into lru_note_cost, since it cycle up on memcg
> tree, for future per lruvec lru_lock replace. It's a bit ugly and may
> cost a bit more locking, but benefit from multiple memcg locking could
> cover the lost.
> 
> Signed-off-by: Alex Shi <alex.shi@...ux.alibaba.com>

Acked-by: Hugh Dickins <hughd@...gle.com>

In your lruv19 github tree, you have merged 14/32 into this one: thanks.

> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: linux-mm@...ck.org
> Cc: linux-kernel@...r.kernel.org
> ---
>  mm/swap.c   | 5 +++--
>  mm/vmscan.c | 4 +---
>  2 files changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/swap.c b/mm/swap.c
> index 906255db6006..f80ccd6f3cb4 100644
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -269,7 +269,9 @@ void lru_note_cost(struct lruvec *lruvec, bool file, unsigned int nr_pages)
>  {
>  	do {
>  		unsigned long lrusize;
> +		struct pglist_data *pgdat = lruvec_pgdat(lruvec);
>  
> +		spin_lock_irq(&pgdat->lru_lock);
>  		/* Record cost event */
>  		if (file)
>  			lruvec->file_cost += nr_pages;
> @@ -293,15 +295,14 @@ void lru_note_cost(struct lruvec *lruvec, bool file, unsigned int nr_pages)
>  			lruvec->file_cost /= 2;
>  			lruvec->anon_cost /= 2;
>  		}
> +		spin_unlock_irq(&pgdat->lru_lock);
>  	} while ((lruvec = parent_lruvec(lruvec)));
>  }
>  
>  void lru_note_cost_page(struct page *page)
>  {
> -	spin_lock_irq(&page_pgdat(page)->lru_lock);
>  	lru_note_cost(mem_cgroup_page_lruvec(page, page_pgdat(page)),
>  		      page_is_file_lru(page), thp_nr_pages(page));
> -	spin_unlock_irq(&page_pgdat(page)->lru_lock);
>  }
>  
>  static void __activate_page(struct page *page, struct lruvec *lruvec)
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index ffccb94defaf..7b7b36bd1448 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1971,19 +1971,17 @@ static int current_may_throttle(void)
>  				&stat, false);
>  
>  	spin_lock_irq(&pgdat->lru_lock);
> -
>  	move_pages_to_lru(lruvec, &page_list);
>  
>  	__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
> -	lru_note_cost(lruvec, file, stat.nr_pageout);
>  	item = current_is_kswapd() ? PGSTEAL_KSWAPD : PGSTEAL_DIRECT;
>  	if (!cgroup_reclaim(sc))
>  		__count_vm_events(item, nr_reclaimed);
>  	__count_memcg_events(lruvec_memcg(lruvec), item, nr_reclaimed);
>  	__count_vm_events(PGSTEAL_ANON + file, nr_reclaimed);
> -
>  	spin_unlock_irq(&pgdat->lru_lock);
>  
> +	lru_note_cost(lruvec, file, stat.nr_pageout);
>  	mem_cgroup_uncharge_list(&page_list);
>  	free_unref_page_list(&page_list);
>  
> -- 
> 1.8.3.1
> 
>