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d=hostedemail.com; s=arc-20220608; t=1772161042; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=BnO3ft+Pk0rGB/9WqfxjOSo4cLnldakpwR0V6eyea0M=; b=0QwyG5BSfddn/uSskttUe+98nOEK/zZdC3CI2KPKzHY16/SW+BH6H0pdwTN5x8Q+ab/pHp bLl/H41qGWHfP5FJHlRzCVDGV/RvRseCjWeiS7NOUni3snHQphCtt2zXEoLZ8yUjjyGvS1 uSrkt92I5qJk4kDZtcFHh4eJQh6RLjY= Received: from mail.maildlp.com (unknown [172.19.163.170]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTPS id 4fMXzN5H6mzYQtj0 for ; Fri, 27 Feb 2026 10:56:48 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.128]) by mail.maildlp.com (Postfix) with ESMTP id 2893D40570 for ; Fri, 27 Feb 2026 10:57:15 +0800 (CST) Received: from huaweicloud.com (unknown [10.50.87.132]) by APP4 (Coremail) with SMTP id gCh0CgBXuPgJCKFpsEGdIw--.32070S7; Fri, 27 Feb 2026 10:57:15 +0800 (CST) From: Ye Bin To: viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, linux-fsdevel@vger.kernel.org Cc: akpm@linux-foundation.org, david@fromorbit.com, zhengqi.arch@bytedance.com, roman.gushchin@linux.dev, muchun.song@linux.dev, linux-mm@kvack.org, yebin10@huawei.com Subject: [PATCH v3 3/3] Documentation: add instructions for using 'drop_fs_caches sysctl' sysctl Date: Fri, 27 Feb 2026 10:55:48 +0800 Message-Id: <20260227025548.2252380-4-yebin@huaweicloud.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260227025548.2252380-1-yebin@huaweicloud.com> References: <20260227025548.2252380-1-yebin@huaweicloud.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CM-TRANSID:gCh0CgBXuPgJCKFpsEGdIw--.32070S7 X-Coremail-Antispam: 1UD129KBjvJXoW7CrW3Gw18ZrWDZw15WF4fuFg_yoW5JFWrpF ZrAryIgw18Xay3WrnxXr47tFyfXay8JFy0q3s7Kr1rZw15CFyj9rsFyw4YqFy7GFW8C3yI qrW5Kwn8Ww1DtFJanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUPFb4IE77IF4wAFF20E14v26rWj6s0DM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28IrcIa0xkI8VA2jI8067AKxVWUWw A2048vs2IY020Ec7CjxVAFwI0_Xr0E3s1l8cAvFVAK0II2c7xJM28CjxkF64kEwVA0rcxS w2x7M28EF7xvwVC0I7IYx2IY67AKxVWDJVCq3wA2z4x0Y4vE2Ix0cI8IcVCY1x0267AKxV W8Jr0_Cr1UM28EF7xvwVC2z280aVAFwI0_GcCE3s1l84ACjcxK6I8E87Iv6xkF7I0E14v2 6rxl6s0DM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40Ex7xfMc Ij6xIIjxv20xvE14v26r106r15McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x0Yz7v_ Jr0_Gr1lF7xvr2IYc2Ij64vIr41lFIxGxcIEc7CjxVA2Y2ka0xkIwI1lc7CjxVAaw2AFwI 0_Jw0_GFyl42xK82IYc2Ij64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxVAqx4xG 67AKxVWUJVWUGwC20s026x8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r1q6r43MI IYrxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_Jr0_JF4lIxAIcVC0I7IYx2IY6xkF7I0E 14v26r4j6F4UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWUCwCI42IY6I8E87Iv67AKxVWUJV W8JwCI42IY6I8E87Iv6xkF7I0E14v26r4j6r4UJbIYCTnIWIevJa73UjIFyTuYvjxUOGQ6 DUUUU X-CM-SenderInfo: p1hex046kxt4xhlfz01xgou0bp/ X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 842001C0005 X-Stat-Signature: xyjiadc6gd5gq1pk1pfyp8g5j5fswnn3 X-Rspam-User: X-HE-Tag: 1772161039-602863 X-HE-Meta: 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 XinzUQ/X JGHXOnjWMlcK2x5ikeIXENgInHD47H6iFwgrXJFexuxcs4VDCzq7ZZOlC9cBFfJBo2tSVWIW2vvtyOPVsHSK1AgWsMHaVFX8yfqInWkOLr5DyDvnYjVu5Sr4GfePLEH/jNfBV+mfH1IcR0uo= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Ye Bin Add instructions for 'drop_fs_caches sysctl' sysctl in 'vm.rst'. Signed-off-by: Ye Bin --- Documentation/admin-guide/sysctl/vm.rst | 44 +++++++++++++++++++++++++ 1 file changed, 44 insertions(+) diff --git a/Documentation/admin-guide/sysctl/vm.rst b/Documentation/admin-guide/sysctl/vm.rst index 97e12359775c..76545da53e20 100644 --- a/Documentation/admin-guide/sysctl/vm.rst +++ b/Documentation/admin-guide/sysctl/vm.rst @@ -37,6 +37,7 @@ Currently, these files are in /proc/sys/vm: - dirtytime_expire_seconds - dirty_writeback_centisecs - drop_caches +- drop_fs_caches - enable_soft_offline - extfrag_threshold - highmem_is_dirtyable @@ -286,6 +287,49 @@ used:: These are informational only. They do not mean that anything is wrong with your system. To disable them, echo 4 (bit 2) into drop_caches. +drop_fs_caches +============== + +Writing to this will cause the kernel to drop clean for a specific file system +caches, as well as reclaimable slab objects like dentries and inodes. Once +dropped, their memory becomes free. Except for specifying the device number +or file path for a specific file system, everything else is consistent with +drop_caches. The device number can be viewed through "cat /proc/self/montinfo" +or 'lsblk'. + +To free pagecache:: + + echo "1 MAJOR:MINOR" > /proc/sys/vm/drop_fs_caches +Or + echo "1 /mnt/XX" > /proc/sys/vm/drop_fs_caches + +To free reclaimable slab objects (includes dentries and inodes):: + + echo "2 MAJOR:MINOR" > /proc/sys/vm/drop_fs_caches +Or + echo "2 /mnt/XX" > /proc/sys/vm/drop_fs_caches + +To free slab objects and pagecache:: + + echo "3 MAJOR:MINOR" > /proc/sys/vm/drop_fs_caches +Or + echo "3 /mnt/XX" > /proc/sys/vm/drop_fs_caches + +You may see error messages in your kernel log when incorrect path or device +number provided:: + + echo (1234): drop_fs_caches: failed to get path(/mnt/XX) ERRNO +Or + echo (1234): drop_fs_caches: failed to get dev(MAJOR:MINOR)'s sb + +You may see informational messages in your kernel log when this file is +used:: + + echo (1234): drop_fs_caches: 3 MAJOR:MINOR + +These are informational only. They do not mean that anything is wrong +with your system. To disable them, echo 4 (bit 2) into drop_fs_caches. + enable_soft_offline =================== Correctable memory errors are very common on servers. Soft-offline is kernel's -- 2.34.1