linux-kernel - Re: [PATCH 03/27] mm, vmstat: Add infrastructure for per-node vmstats

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Message-ID: <20160223181318.GC13816@cmpxchg.org>
Date:	Tue, 23 Feb 2016 10:13:18 -0800
From:	Johannes Weiner <hannes@...xchg.org>
To:	Mel Gorman <mgorman@...hsingularity.net>
Cc:	Linux-MM <linux-mm@...ck.org>, Rik van Riel <riel@...riel.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 03/27] mm, vmstat: Add infrastructure for per-node vmstats

On Tue, Feb 23, 2016 at 03:04:26PM +0000, Mel Gorman wrote:
> VM statistic counters for reclaim decisions are zone-based. If the kernel
> is to reclaim on a per-node basis then we need to track per-node statistics
> but there is no infrastructure for that. The most notable change is that
> the old node_page_state is renamed to sum_zone_node_page_state.  The new
> node_page_state takes a pglist_data and uses per-node stats but none exist
> yet. There is some renaming such as vm_stat to vm_zone_stat and the addition
> of vm_node_stat and the renaming of mod_state to mod_zone_state. Otherwise,
> this is mostly a mechanical patch with no functional change. There is a
> lot of similarity between the node and zone helpers which is unfortunate
> but there was no obvious way of reusing the code and maintaining type safety.
> 
> Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>

Hopefully we can eventually ditch /proc/zoneinfo in favor of a
/proc/nodeinfo and get rid of the per-zone stats accounting.

In general, this patch looks good to me.

Acked-by: Johannes Weiner <hannes@...xchg.org>

Only one thing I noticed:

> @@ -349,12 +349,14 @@ static unsigned long count_shadow_nodes(struct shrinker *shrinker,
>  	shadow_nodes = list_lru_shrink_count(&workingset_shadow_nodes, sc);
>  	local_irq_enable();
>  
> -	if (memcg_kmem_enabled())
> +	if (memcg_kmem_enabled()) {
>  		pages = mem_cgroup_node_nr_lru_pages(sc->memcg, sc->nid,
>  						     LRU_ALL_FILE);
> -	else
> -		pages = node_page_state(sc->nid, NR_ACTIVE_FILE) +
> -			node_page_state(sc->nid, NR_INACTIVE_FILE);
> +	} else {
> +		pg_data_t *pgdat = NODE_DATA(sc->nid);
> +		pages = node_page_state(pgdat, NR_ACTIVE_FILE) +
> +			node_page_state(pgdat, NR_INACTIVE_FILE);
> +	}

That should also be sum_zone_node_page_state, right? These are not
valid node items (yet).