linux-kernel - Re: [PATCH 2/2] mm: Consolidate page table accounting

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Message-Id: <3aabab03-7f0a-e82e-a1c2-79120aed5ace@linux.vnet.ibm.com>
Date:   Thu, 5 Oct 2017 10:38:29 +0530
From:   Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-api@...r.kernel.org, Michal Hocko <mhocko@...nel.org>
Subject: Re: [PATCH 2/2] mm: Consolidate page table accounting

On 10/04/2017 10:06 PM, Kirill A. Shutemov wrote:
> This patch switches page table accounting to single counter from
> three -- nr_ptes, nr_pmds and nr_puds.
> 
> mm->pgtables_bytes is now used to account page table levels. We use
> bytes, because page table size for different levels of page table tree
> may be different.
> 
> The change has user-visible effect: we don't have VmPMD and VmPUD
> reported in /proc/[pid]/status. Not sure if anybody uses them.
> (As alternative, we can always report 0 kB for them.)
> 
> OOM-killer report is also slightly changed: we now report pgtables_bytes
> instead of nr_ptes, nr_pmd, nr_puds.

Could you please mention the motivation of doing this ? Why we are
consolidating the counters which also changes /proc/ interface as
well as OOM report ? What is the benefit ?