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Date: Thu, 19 Mar 2015 13:12:05 +0300
From: Cyrill Gorcunov <gorcunov@gmail.com>
To: Vladimir Davydov <vdavydov@parallels.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Johannes Weiner <hannes@cmpxchg.org>, Michal Hocko <mhocko@suse.cz>,
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        Pavel Emelyanov <xemul@parallels.com>,
        Jonathan Corbet <corbet@lwn.net>, linux-api@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/3] mm: idle memory tracking
Message-ID: <20150319101205.GC27066@moon>
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 <0b70e70137aa5232cce44a69c0b5e320f2745f7d.1426706637.git.vdavydov@parallels.com>
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On Wed, Mar 18, 2015 at 11:44:36PM +0300, Vladimir Davydov wrote:
> Knowing the portion of memory that is not used by a certain application
> or memory cgroup (idle memory) can be useful for partitioning the system
> efficiently. Currently, the only means to estimate the amount of idle
> memory provided by the kernel is /proc/PID/clear_refs. However, it has
> two serious shortcomings:
> 
>  - it does not count unmapped file pages
>  - it affects the reclaimer logic
> 
> This patch attempts to provide the userspace with the means to track
> idle memory without the above mentioned limitations.
...
> +static void set_mem_idle(void)
> +{
> +	int nid;
> +
> +	for_each_online_node(nid)
> +		set_mem_idle_node(nid);
> +}

Vladimir, might we need get_online_mems/put_online_mems here,
or if node gets offline this wont be a problem? (Asking
because i don't know).