From: Theodore Ts'o Subject: [PATCH-v5 0/5] add support for a lazytime mount option Date: Fri, 28 Nov 2014 01:00:05 -0500 Message-ID: <1417154411-5367-1-git-send-email-tytso@mit.edu> Cc: Linux Filesystem Development List , Theodore Ts'o To: Ext4 Developers List Return-path: Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org This is an updated version of what had originally been an ext4-specific patch which significantly improves performance by lazily writing timestamp updates (and in particular, mtime updates) to disk. The in-memory timestamps are always correct, but they are only written to disk when required for correctness. This provides a huge performance boost for ext4 due to how it handles journalling, but it's valuable for all file systems running on flash storage or drive-managed SMR disks by reducing the metadata write load. So upon request, I've moved the functionality to the VFS layer. Once the /sbin/mount program adds support for MS_LAZYTIME, all file systems should be able to benefit from this optimization. There is still an ext4-specific optimization, which may be applicable for other file systems which store more than one inode in a block, but it will require file system specific code. It is purely optional, however. Please note the changes to update_time() and the new write_time() inode operations functions, which impact btrfs and xfs. The changes are fairly simple, but I would appreciate confirmation from the btrfs and xfs teams that I got things right. Thanks!! Changes since -v4: - Fix ext4 optimization so it does not need to increment (and more problematically, decrement) the inode reference count - Per Christoph's suggestion, drop support for btrfs and xfs for now, issues with how btrfs and xfs handle dirty inode tracking. We can add btrfs and xfs support back later or at the end of this series if we want to revisit this decision. - Miscellaneous cleanups Changes since -v3: - inodes with I_DIRTY_TIME set are placed on a new bdi list, b_dirty_time. This allows filesystem-level syncs to more easily iterate over those inodes that need to have their timestamps written to disk. - dirty timestamps will be written out asynchronously on the final iput, instead of when the inode gets evicted. - separate the definition of the new function find_active_inode_nowait() to a separate patch - create separate flag masks: I_DIRTY_WB and I_DIRTY_INODE, which indicate whether the inode needs to be on the write back lists, or whether the inode itself is dirty, while I_DIRTY means any one of the inode dirty flags are set. This simplifies the fs writeback logic which needs to test for different combinations of the inode dirty flags in different places. Changes since -v2: - If update_time() updates i_version, it will not use lazytime (i..e, the inode will be marked dirty so the change will be persisted on to disk sooner rather than later). Yes, this eliminates the benefits of lazytime if the user is experting the file system via NFSv4. Sad, but NFS's requirements seem to mandate this. - Fix time wrapping bug 49 days after the system boots (on a system with a 32-bit jiffies). Use get_monotonic_boottime() instead. - Clean up type warning in include/tracing/ext4.h - Added explicit parenthesis for stylistic reasons - Added an is_readonly() inode operations method so btrfs doesn't have to duplicate code in update_time(). Changes since -v1: - Added explanatory comments in update_time() regarding i_ts_dirty_days - Fix type used for days_since_boot - Improve SMP scalability in update_time and ext4_update_other_inodes_time - Added tracepoints to help test and characterize how often and under what circumstances inodes have their timestamps lazily updated Theodore Ts'o (5): vfs: add support for a lazytime mount option vfs: don't let the dirty time inodes get more than a day stale vfs: add lazytime tracepoints for better debugging vfs: add find_inode_nowait() function ext4: add optimization for the lazytime mount option fs/ext4/inode.c | 66 +++++++++++++++++++++++-- fs/ext4/super.c | 9 ++++ fs/fs-writeback.c | 66 ++++++++++++++++++++++--- fs/inode.c | 116 +++++++++++++++++++++++++++++++++++++++++--- fs/libfs.c | 2 +- fs/logfs/readwrite.c | 2 +- fs/nfsd/vfs.c | 2 +- fs/pipe.c | 2 +- fs/proc_namespace.c | 1 + fs/sync.c | 8 +++ fs/ufs/truncate.c | 2 +- include/linux/backing-dev.h | 1 + include/linux/fs.h | 17 ++++++- include/trace/events/ext4.h | 30 ++++++++++++ include/trace/events/fs.h | 56 +++++++++++++++++++++ include/uapi/linux/fs.h | 1 + mm/backing-dev.c | 10 +++- 17 files changed, 367 insertions(+), 24 deletions(-) create mode 100644 include/trace/events/fs.h -- 2.1.0