linux-kernel - Re: [PATCH v9 1/1] mm: report per-page metadata information

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Message-ID: <CA+CK2bAqdFL-kGmTR8msdy_FSr4Zt7+riJgjdTxX+FN+-M0pLA@mail.gmail.com>
Date: Wed, 13 Mar 2024 18:37:55 -0400
From: Pasha Tatashin <pasha.tatashin@...een.com>
To: Wei Xu <weixugc@...gle.com>
Cc: 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, david@...hat.com, 
	rdunlap@...radead.org, chenlinxuan@...ontech.com, yang.yang29@....com.cn, 
	tomas.mudrunka@...il.com, bhelgaas@...gle.com, ivan@...udflare.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, 
	willy@...radead.org
Subject: Re: [PATCH v9 1/1] mm: report per-page metadata information

On Mon, Feb 26, 2024 at 1:12 PM Wei Xu <weixugc@...gle.com> wrote:
>
> On Tue, Feb 20, 2024 at 1:46 PM Sourav Panda <souravpanda@...gle.com> wrote:
> >
> > Adds two new per-node fields, namely nr_memmap and nr_memmap_boot,
> > to /sys/devices/system/node/nodeN/vmstat and a global Memmap 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.
>
> /proc/vmstat also has the system-wide nr_memmap and nr_memmap_boot.
> Given that nr_memmap in /proc/vmstat provides the same info (in
> different units) as Memmap in /proc/meminfo, it would be better to
> remove Memmap from /proc/meminfo to avoid duplication and confusion.

There are many items both in meminfo and in vmstat. Given that
/proc/meminfo covers all kmem memory, it is beneficial to keep the
kmem part of memmap in meminfo as another classification item.

Pasha