linux-kernel - Re: [PATCH v8 1/1] mm: report per-page metadata information

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Message-ID: <CA+CK2bDH9E_nHs4FVYxuOUcddL_asOTTXHJd1FuVmGfEGNeZXw@mail.gmail.com>
Date: Thu, 15 Feb 2024 19:51:37 -0500
From: Pasha Tatashin <pasha.tatashin@...een.com>
To: Suren Baghdasaryan <surenb@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Sourav Panda <souravpanda@...gle.com>, corbet@....net, 
	gregkh@...uxfoundation.org, rafael@...nel.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, 
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org, 
	linux-doc@...r.kernel.org, linux-mm@...ck.org, willy@...radead.org, 
	weixugc@...gle.com
Subject: Re: [PATCH v8 1/1] mm: report per-page metadata information

On Thu, Feb 15, 2024 at 7:40 PM Suren Baghdasaryan <surenb@...gle.com> wrote:
>
> On Thu, Feb 15, 2024 at 4:14 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
> >
> > On Wed, 14 Feb 2024 14:57:40 -0800 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.
> >
> > Would this information be available by the proposed memory
> > allocation profiling?
>
> Well, not without jumping through the hoops. You would need to find
> the places in the source code where all this matadata is allocated and
> find the appropriate records inside /proc/allocinfo file.

Another difference is that memory allocation profiling does not report
memblock allocated memory, this patch reports the amount of per-page
metadata allocated by the memblock allocator in addition to various
paths that are used to allocate per-page metdata after the buddy
allocator is initialized. Also, the memory profiling has page_ext
overhead, so it is not practical to unconditionally enable it
throughout the fleet.

Pasha