linux-kernel - Re: [PATCH 3/6] mm: memcontrol: replace node summing with memcg_page

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Message-Id: <20190321185453.6458679180e1e41893e7312b@linux-foundation.org>
Date:   Thu, 21 Mar 2019 18:54:53 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Johannes Weiner <hannes@...xchg.org>
Cc:     Tejun Heo <tj@...nel.org>, Roman Gushchin <guro@...com>,
        linux-mm@...ck.org, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-team@...com
Subject: Re: [PATCH 3/6] mm: memcontrol: replace node summing with
 memcg_page_state()

On Thu, 28 Feb 2019 11:30:17 -0500 Johannes Weiner <hannes@...xchg.org> wrote:

> Instead of adding up the node counters, use memcg_page_state() to get
> the memcg state directly. This is a bit cheaper and more stream-lined.
> 
> ...
>
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -746,10 +746,13 @@ static unsigned long mem_cgroup_nr_lru_pages(struct mem_cgroup *memcg,
>  			unsigned int lru_mask)
>  {
>  	unsigned long nr = 0;
> -	int nid;
> +	enum lru_list lru;
>  
> -	for_each_node_state(nid, N_MEMORY)
> -		nr += mem_cgroup_node_nr_lru_pages(memcg, nid, lru_mask);
> +	for_each_lru(lru) {
> +		if (!(BIT(lru) & lru_mask))
> +			continue;
> +		nr += memcg_page_state(memcg, NR_LRU_BASE + lru);
> +	}

Might be able to use for_each_set_bit(&lru_mnask) here, but it's much
of a muchness.