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Fri, 13 Feb 2026 06:52:39 -0800 (PST) MIME-Version: 1.0 References: <20260210043456.2137482-1-haowenchao22@gmail.com> <5c4d773c-e3e7-4a71-b250-91701cbdd4a2@kernel.org> <201fcbb4-c43c-406c-ad54-f2c9301c12b0@kernel.org> In-Reply-To: From: Wenchao Hao Date: Fri, 13 Feb 2026 22:52:28 +0800 X-Gm-Features: AZwV_QjFh_hBIesWneXx_AGXafgFmkb2lL8_tH60Wk2lj6ZVnsRw1UVpkSgrwRM Message-ID: Subject: Re: [RFC PATCH] mm: only set fault addrsss' access bit in do_anonymous_page To: "David Hildenbrand (Arm)" Cc: Andrew Morton , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: D35FA100014 X-Stat-Signature: 7uqechc5xbb7811x1ikhsxap8pn9yoap X-Rspam-User: X-HE-Tag: 1770994360-446899 X-HE-Meta: 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 WBqEMBvA IQ/YTIbWwKFzsHMYFlLNaRxd8eg61rJpFx683a8qc90cZ8tqtkYd3wAOaqv5grFbyYfl2iAkjL6WG4KRcrIRDHGujaTbipesfMVoSc9qsKhAUb2h40YfpsHt8VIW36SIA9uCjtqyg0KvrzvNPy9n9yZqoRZ1nHB7uB58ZkA2iayHeCBffjBXA4FCkQUa4seQ8zkG9T89QQY9EE9o1PZorHQMnWkTErVF6AYKHH67/0o21S4ZvRFmXoVMrWH9PWLcY+9gQG5cTn61ojPJzNSe/EtD/wqonwann9CI9a9VdeGwK2jlnxKxyy5CKL4xnj/6m4v/Wb+U2z+4D6RsYeMbn9qFJcQVwiKJbMDrV3o0s9K1aarf7pfm334SqPxFVMPpXdAliJhxy0BUFgtbuFS37Z9V/QxTDsWTeA+2eV8DIjCoBFYFZZV9dY6UhJWG5SX8fzIIFmo4kOa68upUfcGPm+guZzw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Feb 13, 2026 at 5:08=E2=80=AFPM David Hildenbrand (Arm) wrote: > > On 2/13/26 10:02, Wenchao Hao wrote: > > On Thu, Feb 12, 2026 at 4:54=E2=80=AFPM David Hildenbrand (Arm) > > wrote: > >> > >> On 2/12/26 02:57, Wenchao Hao wrote: > >>> On Wed, Feb 11, 2026 at 5:05=E2=80=AFPM David Hildenbrand (Arm) > >>> wrote: > >>> > >>> Thanks for your explanation. I now understand the design logic. > >>> > >>> What I=E2=80=99m proposing is mainly for debugging. After enabling 64= K large folio > >>> on Android, we observed increased application memory footprint, espec= ially > >>> for anonymous pages. > >>> > >>> Since Android app memory usage depends on runtime scenarios, we canno= t > >>> confirm if the growth is directly caused by large folio. We want to > >>> analyze memory > >>> usage via the `Referenced` field in `/proc/[pid]/smaps`. > >> > >> Scanning for zero-filled pages will be much easier and more reliable. > >> For a debug feature good enough. > >> > >> I'm wondering what the best interface for something like that could be= : > >> we don't want to make "/proc/[pid]/smaps" slower for all users. > >> > >> Maybe we could for debug kernels. > >> > >> For example, adding with CONFIG_DEBUG_KERNEL a new entry > >> > >> Anon_Zero: > >> > >> counter that just tests whether the page content of an anonymous page = is > >> all zeroes could be doable. > >> > > > > Apologies for the delayed reply =E2=80=93 I was just writing a demo to = verify the > > approach you mentioned. > > > > Using the CONFIG_DEBUG_KERNEL compile-time macro to isolate this featur= e > > is indeed an excellent idea. > > > > However, in engineering practice, it requires recompiling and > > replacing the kernel, > > which can be cumbersome. Could we instead use a dynamic switch to contr= ol > > whether scan for zero-filled pages when reading /proc/[pid]/smaps? > > Maybe a kernel cmdline option could do? Kernel command line parameters can meet our requirements. > Selectively enabling it for some PIDs only is not really possible, but al= so, maybe it's not really needed. Yes, it is unnecessary to do that. By the way, will you send a new patch for this, or shall I take care of it? Thanks. > > -- > Cheers, > > David