From: Andreas Dilger Subject: Re: Documenting MS_LAZYTIME Date: Fri, 20 Feb 2015 05:32:58 -0700 Message-ID: <44893EA7-B11A-469A-9911-6CE2E8B26EB4@dilger.ca> References: Mime-Version: 1.0 (Mac OS X Mail 8.2 \(2070.6\)) Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Theodore Ts'o , Ext4 Developers List , Linux btrfs Developers List , XFS Developers , linux-man-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Linux-Fsdevel , Linux API To: Michael Kerrisk Return-path: In-Reply-To: Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-ext4.vger.kernel.org On Feb 20, 2015, at 1:50 AM, Michael Kerrisk w= rote: >=20 > Hello Ted, >=20 > Based on your commit message 0ae45f63d4e, I I wrote the documentation > below for MS_LAZYTIME, to go into the mount(2) man page. Could you > please check it over and let me know if it's accurate. In particular, > I added pieces marked with "*" below that were not part of the commit > message and I'd like confirmation that they're accurate. >=20 > Thanks, >=20 > Michael >=20 > [[ > MS_LAZYTIME (since Linux 3.20) > Only update filetimes (atime, mtime, ctime) on the in- > memory version of the file inode. The on-disk time=E2= =80=90 > stamps are updated only when: >=20 > (a) the inode needs to be updated for some change unre=E2= =80=90 > lated to file timestamps; >=20 > (b) the application employs fsync(2), syncfs(2), or > sync(2); >=20 > (c) an undeleted inode is evicted from memory; or >=20 > * (d) more than 24 hours have passed since the i-node wa= s > * written to disk. >=20 > This mount option significantly reduces writes to the > inode table for workloads that perform frequent random > writes to preallocated files. >=20 > * As at Linux 3.20, this option is supported only on ext4= =2E I _think_ that the lazytime mount option is generic for all filesystems= =2E I believe ext4 has an extra optimization for it, but that's it. Cheers, Andreas