Received-SPF: pass (google.com: domain of linux-kernel+bounces-108157-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.199.223 as permitted sender) client-ip=147.75.199.223;
Date: Tue, 19 Mar 2024 14:33:20 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Sourav Panda <souravpanda@google.com>
Cc: corbet@lwn.net, gregkh@linuxfoundation.org, rafael@kernel.org,
 mike.kravetz@oracle.com, muchun.song@linux.dev, rppt@kernel.org,
 david@redhat.com, rdunlap@infradead.org, chenlinxuan@uniontech.com,
 yang.yang29@zte.com.cn, tomas.mudrunka@gmail.com, bhelgaas@google.com,
 ivan@cloudflare.com, pasha.tatashin@soleen.com, yosryahmed@google.com,
 hannes@cmpxchg.org, shakeelb@google.com, kirill.shutemov@linux.intel.com,
 wangkefeng.wang@huawei.com, adobriyan@gmail.com, vbabka@suse.cz,
 Liam.Howlett@Oracle.com, surenb@google.com, linux-kernel@vger.kernel.org,
 linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org,
 linux-mm@kvack.org, willy@infradead.org, weixugc@google.com
Subject: Re: [PATCH v9 1/1] mm: report per-page metadata information
Message-Id: <20240319143320.d1b1ef7f6fa77b748579ba59@linux-foundation.org>
In-Reply-To: <20240220214558.3377482-2-souravpanda@google.com>
References: <20240220214558.3377482-1-souravpanda@google.com>
	<20240220214558.3377482-2-souravpanda@google.com>
Precedence: bulk
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit

On Tue, 20 Feb 2024 13:45:58 -0800 Sourav Panda <souravpanda@google.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.

I yield to no man in my admiration of changelogging but boy, that's a
lot of changelogging.  Would it be possible to consolidate the [0/N]
coverletter and the [1/N] changelog into a single thing please?

>  Documentation/filesystems/proc.rst |  3 +++
>  fs/proc/meminfo.c                  |  4 ++++
>  include/linux/mmzone.h             |  4 ++++
>  include/linux/vmstat.h             |  4 ++++
>  mm/hugetlb_vmemmap.c               | 17 ++++++++++++----
>  mm/mm_init.c                       |  3 +++
>  mm/page_alloc.c                    |  1 +
>  mm/page_ext.c                      | 32 +++++++++++++++++++++---------
>  mm/sparse-vmemmap.c                |  8 ++++++++
>  mm/sparse.c                        |  7 ++++++-
>  mm/vmstat.c                        | 26 +++++++++++++++++++++++-
>  11 files changed, 94 insertions(+), 15 deletions(-)

And yet we offer the users basically no documentation.  The new sysfs
file should be documented under Documentation/ABI somewhere and
perhaps we could prepare some more expansive user-facing documentation
elsewhere?

I'd like to hear others' views on the overall usefulness/utility of this
change, please?