linux-kernel - Re: [PATCH v4 19/25] proc/task_mmu: Ignore ZONE

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Message-ID: <c7bd9b00-6920-4dc0-8e2e-36c16ef7ad5a@redhat.com>
Date: Tue, 17 Dec 2024 23:31:25 +0100
From: David Hildenbrand <david@...hat.com>
To: Alistair Popple <apopple@...dia.com>, akpm@...ux-foundation.org,
 dan.j.williams@...el.com, linux-mm@...ck.org
Cc: lina@...hilina.net, zhang.lyra@...il.com, gerald.schaefer@...ux.ibm.com,
 vishal.l.verma@...el.com, dave.jiang@...el.com, logang@...tatee.com,
 bhelgaas@...gle.com, jack@...e.cz, jgg@...pe.ca, catalin.marinas@....com,
 will@...nel.org, mpe@...erman.id.au, npiggin@...il.com,
 dave.hansen@...ux.intel.com, ira.weiny@...el.com, willy@...radead.org,
 djwong@...nel.org, tytso@....edu, linmiaohe@...wei.com, peterx@...hat.com,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linuxppc-dev@...ts.ozlabs.org,
 nvdimm@...ts.linux.dev, linux-cxl@...r.kernel.org,
 linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
 linux-xfs@...r.kernel.org, jhubbard@...dia.com, hch@....de,
 david@...morbit.com
Subject: Re: [PATCH v4 19/25] proc/task_mmu: Ignore ZONE_DEVICE pages

On 17.12.24 06:13, Alistair Popple wrote:
> The procfs mmu files such as smaps currently ignore device dax and fs
> dax pages because these pages are considered special. To maintain
> existing behaviour once these pages are treated as normal pages and
> returned from vm_normal_page() add tests to explicitly skip them.
> 
> Signed-off-by: Alistair Popple <apopple@...dia.com>
> ---
>   fs/proc/task_mmu.c | 18 ++++++++++++++----
>   1 file changed, 14 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 38a5a3e..c9b227a 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -801,6 +801,8 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr,
>   
>   	if (pte_present(ptent)) {
>   		page = vm_normal_page(vma, addr, ptent);
> +		if (page && (is_device_dax_page(page) || is_fsdax_page(page)))

This "is_device_dax_page(page) || is_fsdax_page(page)" is a common theme 
here, likely we should have a special helper?


But, don't we actually want to include them in the smaps output now? I 
think we want.

The rmap code will indicate these pages in /proc/meminfo, per-node info, 
in the memcg ... as "Mapped:" etc.

So likely we just want to also indicate them here, or is there any 
downsides we know of?

-- 
Cheers,

David / dhildenb