linux-kernel - Re: [PATCH v1 1/1] mm: report per-page metadata information

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Message-ID: <5d6a780e-2945-2b24-bca6-3e38565fe157@redhat.com>
Date:   Thu, 14 Sep 2023 15:00:18 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Sourav Panda <souravpanda@...gle.com>, corbet@....net,
        gregkh@...uxfoundation.org, rafael@...nel.org,
        akpm@...ux-foundation.org, mike.kravetz@...cle.com,
        muchun.song@...ux.dev, rppt@...nel.org, rdunlap@...radead.org,
        chenlinxuan@...ontech.com, yang.yang29@....com.cn,
        tomas.mudrunka@...il.com, bhelgaas@...gle.com, ivan@...udflare.com,
        pasha.tatashin@...een.com, yosryahmed@...gle.com,
        hannes@...xchg.org, shakeelb@...gle.com,
        kirill.shutemov@...ux.intel.com, wangkefeng.wang@...wei.com,
        adobriyan@...il.com, vbabka@...e.cz, Liam.Howlett@...cle.com,
        surenb@...gle.com, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH v1 1/1] mm: report per-page metadata information

On 13.09.23 19:30, Sourav Panda wrote:
> Adds a new per-node PageMetadata field to
> /sys/devices/system/node/nodeN/meminfo
> and a global PageMetadata field to /proc/meminfo. This information can
> be used by users to see how much memory is being used by per-page
> metadata, which can vary depending on build configuration, machine
> architecture, and system use.
> 
> Per-page metadata is the amount of memory that Linux needs in order to
> manage memory at the page granularity. The majority of such memory is
> used by "struct page" and "page_ext" data structures.

It's probably worth mentioning, that in contrast to most other "memory 
consumption" statistics, this metadata might not be included "MemTotal"; 
when the memmap is allocated using the memblock allocator, it's not 
included, when it's dynamically allocated using the buddy (e.g., memory 
hotplug), it's included.

-- 
Cheers,

David / dhildenb