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(unknown []) by gzsmtp3 (Coremail) with SMTP id PigvCgCHsO+nu2Vpjun8LA--.33S2; Tue, 13 Jan 2026 11:27:38 +0800 (CST) From: ranxiaokai627@163.com To: kent.overstreet@linux.dev Cc: Liam.Howlett@oracle.com, akpm@linux-foundation.org, corbet@lwn.net, david@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com, mhocko@suse.com, ran.xiaokai@zte.com.cn, ranxiaokai627@163.com, rppt@kernel.org, surenb@google.com, vbabka@suse.cz Subject: Re: [PATCH] alloc_tag: remove sysctl prefix from mem_profiling boot parameter Date: Tue, 13 Jan 2026 03:27:35 +0000 Message-ID: <20260113032735.161838-1-ranxiaokai627@163.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CM-TRANSID:PigvCgCHsO+nu2Vpjun8LA--.33S2 X-Coremail-Antispam: 1Uf129KBjvJXoW7AFWfuFWDGr4rKry7trWrXwb_yoW8uF45pF WkGF18tr1kJ3s2kr17Aw1IgrySyr48Jr4aqw1DWrW0ywnrWF92vrWI9FWSyFnrWr93Ca18 Xa1ava40vw4jv37anT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x0JUo5lUUUUUU= X-Originating-IP: [117.176.243.29] X-CM-SenderInfo: xudq5x5drntxqwsxqiywtou0bp/xtbCxQrMGWllu6oN3QAA3X X-Stat-Signature: h7i7cjysunmp71gyzweoyna5ore6q4zy X-Rspamd-Queue-Id: 0C670140007 X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1768274875-677756 X-HE-Meta: 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 +Bo/KiGy 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 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, Jan 09, 2026 at 06:24:19AM +0000, ranxiaokai627@163.com wrote: >> From: Ran Xiaokai >> >> Boot parameters prefixed with "sysctl." are processed separately >> during the final stage of system initialization via kernel_init()-> >> do_sysctl_args(). Since mem_profiling support should be parsed >> in early boot stage, it is unsuitable for centralized handling >> in do_sysctl_args(). >> Also, when CONFIG_MEM_ALLOC_PROFILING_DEBUG is enabled, >> the sysctl.vm.mem_profiling entry is not writable and will cause >> a warning. To prevent duplicate processing of sysctl.vm.mem_profiling, >> rename the boot parameter to "mem_profiling". >> >> Signed-off-by: Ran Xiaokai > >How was this observed/detected? Actually no kernel bug or funtional defect was observed through testing. Via code reading, i found after commit [1], boot parameters prefixed with sysctl is processed redundantly. [1] https://lore.kernel.org/all/20200427180433.7029-3-vbabka@suse.cz/T/#u >My reading of early_param() would seem to indicate that >setup_early_mem_profiling() is getting called at the appropriate time - >and then additionally a second time by do_sysctl_args(), which then >becomes a noop. In the handling of process_sysctl_arg(), it at least needs to call kern_mount("proc"), file_open_root_mnt("/proc/sys/vm/xxx"), kernel_write(), and filp_close() for processing. I dont quite understand why it was optimized into a noop. >So the only bug would seem to be that the sysctl is not writeable in >debug mode? There's an easier fix for that one... - When debug mode is enabled, a warning is triggered because the file is not writable. - When debug mode is disabled, do_sysctl_args() cannot handle boot parameters like "1,compressed". It only accepts writes of 0 or 1. As mem_profiling should be parsed in early boot, so this makes it unsuitable for processing in do_sysctl_args(), which is why I have renamed the parameter. But as Andrew mentioned, I did not consider the backward compatibility issues.