Date: Wed, 29 Apr 2015 14:02:47 +0900
From: Minchan Kim <minchan@kernel.org>
To: Vladimir Davydov <vdavydov@parallels.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Johannes Weiner <hannes@cmpxchg.org>, Michal Hocko <mhocko@suse.cz>,
        Greg Thelen <gthelen@google.com>,
        Michel Lespinasse <walken@google.com>,
        David Rientjes <rientjes@google.com>,
        Pavel Emelyanov <xemul@parallels.com>,
        Cyrill Gorcunov <gorcunov@openvz.org>,
        Jonathan Corbet <corbet@lwn.net>, linux-api@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 0/3] idle memory tracking
Message-ID: <20150429050247.GB27051@blaptop>
References: <cover.1430217477.git.vdavydov@parallels.com>
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On Tue, Apr 28, 2015 at 03:24:39PM +0300, Vladimir Davydov wrote:
> Hi,
> 
> This patch set introduces a new user API for tracking user memory pages
> that have not been used for a given period of time. The purpose of this
> is to provide the userspace with the means of tracking a workload's
> working set, i.e. the set of pages that are actively used by the
> workload. Knowing the working set size can be useful for partitioning
> the system more efficiently, e.g. by tuning memory cgroup limits
> appropriately, or for job placement within a compute cluster.
> 
> ---- USE CASES ----
> 
> The unified cgroup hierarchy has memory.low and memory.high knobs, which
> are defined as the low and high boundaries for the workload working set
> size. However, the working set size of a workload may be unknown or
> change in time. With this patch set, one can periodically estimate the
> amount of memory unused by each cgroup and tune their memory.low and
> memory.high parameters accordingly, therefore optimizing the overall
> memory utilization.
> 
> Another use case is balancing workloads within a compute cluster.
> Knowing how much memory is not really used by a workload unit may help
> take a more optimal decision when considering migrating the unit to
> another node within the cluster.

Another usecase I have a interest is working with per-process reclaim.
https://lwn.net/Articles/545668/
With idle tracking, we could reclaim idle pages only by smart user
memory-manager.

Thanks.

-- 
Kind regards,
Minchan Kim
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