linux-kernel - Re: [PATCH 31/31] mm, vmstat: Remove zone and node double accounting by approximating retries

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Date:	Thu, 7 Jul 2016 12:26:20 +0100
From:	Mel Gorman <mgorman@...hsingularity.net>
To:	Dave Hansen <dave.hansen@...el.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux-MM <linux-mm@...ck.org>, Rik van Riel <riel@...riel.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 31/31] mm, vmstat: Remove zone and node double accounting
 by approximating retries

On Wed, Jul 06, 2016 at 11:12:52AM -0700, Dave Hansen wrote:
> On 07/01/2016 01:01 PM, Mel Gorman wrote:
> > +#ifdef CONFIG_HIGHMEM
> > +extern unsigned long highmem_file_pages;
> > +
> > +static inline void acct_highmem_file_pages(int zid, enum lru_list lru,
> > +							int nr_pages)
> > +{
> > +	if (is_highmem_idx(zid) && is_file_lru(lru))
> > +		highmem_file_pages += nr_pages;
> > +}
> > +#else
> 
> Shouldn't highmem_file_pages technically be an atomic_t (or atomic64_t)?
>  We could have highmem on two nodes which take two different LRU locks.

It would require a NUMA machine with highmem or very weird
configurations but sure, atomic is safer.

-- 
Mel Gorman
SUSE Labs