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Date: Tue, 30 Aug 2016 10:15:34 +0200
From: Michal Hocko <mhocko@kernel.org>
To: Sonny Rao <sonnyrao@chromium.org>
Cc: Jann Horn <jann@thejh.net>, Robert Foss <robert.foss@collabora.com>,
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Subject: Re: [PACTH v2 0/3] Implement /proc/<pid>/totmaps
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On Mon 29-08-16 16:37:04, Michal Hocko wrote:
> [Sorry for a late reply, I was busy with other stuff]
> 
> On Mon 22-08-16 15:44:53, Sonny Rao wrote:
> > On Mon, Aug 22, 2016 at 12:54 AM, Michal Hocko <mhocko@kernel.org> wrote:
> [...]
> > But what about the private_clean and private_dirty?  Surely
> > those are more generally useful for calculating a lower bound on
> > process memory usage without additional knowledge?
> 
> I guess private_clean can be used as a reasonable estimate.

I was thinking about this more and I think I am wrong here. Even truly
MAP_PRIVATE|MAP_ANON will be in private_dirty. So private_clean will
become not all that interesting and similarly misleading as its _dirty
variant (mmaped file after [m]sync should become _clean) and that
doesn't mean the memory will get freed after the process which maps it
terminates. Take shmem as an example again.

> private_dirty less so because it may refer to e.g. tmpfs which is not
> mapped by other process and so no memory would be freed after unmap
> without removing the file.

-- 
Michal Hocko
SUSE Labs