linux-kernel - Re: [PATCHv3 1/2] proc: mm: export PTE sizes directly in smaps

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Message-ID: <10bc2525-fccc-81e6-1ec0-27d63cff89b4@intel.com>
Date:   Thu, 26 Oct 2017 07:25:37 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Michal Hocko <mhocko@...nel.org>, "Du, Fan" <fan.du@...el.com>
Cc:     "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "hch@....de" <hch@....de>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>
Subject: Re: [PATCHv3 1/2] proc: mm: export PTE sizes directly in smaps

On 10/26/2017 07:19 AM, Michal Hocko wrote:
>> Current vm_normal_page implementation doesn't pick up page with DEVMAP pfn.
>> The second patch fix this and export DAX mappings into counters introduced in the
>> first patch.
>>
>> IMO, the user care more about how much persistent memory they used, how about
>> a small tweak with smaps_account, and report the total mapping size into RSS/PSS,
>> which user are usually more familiar with?
> No! Rss and pss is already used by many tools to evaluate misbehaving
> tasks. If you start accounting the memory which is not bound to the
> process life time then you can break those usecases. This is the reason
> why hugetlb is not accounted to rss as well.

Yeah, folks (rightly) assume Rss is memory and eaten from MemTotal.  DAX
mappings do not use RAM.