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b=PPguWuDxV90WFW4FyKTJraT08uHhvn0/gt+Plk+13SLUmCX7/Oc9r6Zj7Z2tT4IK1 hraku9eA24FpFJw9I6qP+3wMZIcWV21rux5ALfze4LNKVTQisK725WzSnPy2rzCr0b 55ifH/89+CEiDxP+pjauFr8TcBnlUKGKuha7TaQA= Date: Mon, 21 Apr 2025 11:26:50 -0700 From: Andrew Morton To: Mike Rapoport Cc: Ruihan Li , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mm/mm_init: Don't iterate pages below ARCH_PFN_OFFSET Message-Id: <20250421112650.4fe689205944ccdaf078ca28@linux-foundation.org> In-Reply-To: References: <20250419122801.1752234-1-lrh2000@pku.edu.cn> <20250420135709.732883ee775ad8b41fb668ca@linux-foundation.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: 1geuzjfybija8yekdbaxy438ja3xwn46 X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 55F1320004 X-Rspam-User: X-HE-Tag: 1745260012-657154 X-HE-Meta: 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 u6FmMHI0 HsIy+nscCEfXKLmfnFIeC5J5APPmACD96jp0/lt3+H5YW6Oxg/er1cwp7jU6UtaT8dPMY4XNbQG5ptneZaMnH5B6zSkTMroZEpVaK2gpbINAbX6KiL85wR4aBJdtcKrw3VK0UGgRfWlUgBu9eDYlaEOlbpJzzVDL+tb5egbi3OecCYfWhDICJ+n/ieIw8mrNOymCYB6gv8TjY1JDDDBAcVTPtpOZWVcwVX+5YTGNbG0IuVhM7SD7Jy1mPJYiXRbhLA+IbHdcHsu1mGw7g9XwC+c+eAKj/5TeOVKB5gorEFoEXyjAyUsjITjh/Fk6ZnlFqx8bE 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 Mon, 21 Apr 2025 19:35:25 +0300 Mike Rapoport wrote: > On Sun, Apr 20, 2025 at 01:57:09PM -0700, Andrew Morton wrote: > > On Sat, 19 Apr 2025 20:28:01 +0800 Ruihan Li wrote: > > > > > If ARCH_PFN_OFFSET is very large (e.g., something like 2^64-2GiB if the > > > kernel is used as a library and loaded at a very high address), the > > > pointless iteration for pages below ARCH_PFN_OFFSET will take a very > > > long time, and the kernel will look stuck at boot time. > > > > > > This commit sets the initial value of pfn_hole to ARCH_PFN_OFFSET, which > > > avoids the problematic and useless iteration mentioned above. > > > > > > This problem has existed since commit 907ec5fca3dc ("mm: zero remaining > > > unavailable struct pages"). > > > > > > Signed-off-by: Ruihan Li > > > --- > > > Link to v1: > > > - https://lore.kernel.org/linux-mm/20250418162727.1535335-1-lrh2000@pku.edu.cn/ > > > Changes since v1: > > > - Removed the unnecessary Fixes tag. > > > > Why was the Fixes: considered unnecessary? It seems to be useful > > information? > > I didn't think it was important enough for AUTOSEL to pick it. They've been asked not to backport MM patches unless they have an explicit cc:stable.