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Date: Fri, 28 Nov 2014 09:55:19 +0100 From: Sedat Dilek <sedat.dilek@...il.com> To: "Theodore Ts'o" <tytso@....edu> Cc: Ext4 Developers List <linux-ext4@...r.kernel.org>, Linux Filesystem Development List <linux-fsdevel@...r.kernel.org> Subject: Re: [PATCH-v5 0/5] add support for a lazytime mount option On Fri, Nov 28, 2014 at 7:00 AM, Theodore Ts'o <tytso@....edu> wrote: > 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!! > Some questions... on how to test this... [ Base ] Is this patchset on top of ext4-next (ext4.git#dev)? Might someone test on top of Linux v3.18-rc6 with pulled in ext4.git#dev2? [ Userland ] Do I need an updated userland (/sbin/mount)? IOW, adding "lazytime" to my ext4-line(s) in /etc/fstab is enough? [ Benchmarks ] Do you have numbers - how big/fast is the benefit? On a desktop machine? Thanks in advance. - Sedat - > 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 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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