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From: bfields@fieldses.org (J. Bruce Fields)
To: Jeff Layton <jlayton@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-nfs@vger.kernel.org, linux-ext4@vger.kernel.org,
	linux-btrfs@vger.kernel.org, linux-xfs@vger.kernel.org
Subject: Re: [RFC PATCH v1 00/30] fs: inode->i_version rework and optimization
Date: Mon, 20 Mar 2017 17:43:27 -0400	[thread overview]
Message-ID: <20170320214327.GA5098@fieldses.org> (raw)
In-Reply-To: <1482417724.3924.39.camel@redhat.com>

On Thu, Dec 22, 2016 at 09:42:04AM -0500, Jeff Layton wrote:
> On Thu, 2016-12-22 at 00:45 -0800, Christoph Hellwig wrote:
> > On Wed, Dec 21, 2016 at 12:03:17PM -0500, Jeff Layton wrote:
> > > 
> > > Only btrfs, ext4, and xfs implement it for data changes. Because of
> > > this, these filesystems must log the inode to disk whenever the
> > > i_version counter changes. That has a non-zero performance impact,
> > > especially on write-heavy workloads, because we end up dirtying the
> > > inode metadata on every write, not just when the times change. [1]
> > 
> > Do you have numbers to justify these changes?
> 
> I have numbers. As to whether they justify the changes, I'm not sure.
> This helps a lot on a (admittedly nonsensical) 1-byte write workload. On
> XFS, with this fio jobfile:

To me, the interesting question is whether this allows us to turn on
i_version updates by default on xfs and ext4.

When Josef looked at doing that previously he withdrew the patch due to
performance regressions.  I think the most useful thread started here:

	http://lkml.kernel.org/r/1337092396-3272-1-git-send-email-josef@redhat.com

Skimming quickly....  I think the regression was also in the small-write
case.  So apparently that was thought to reveal a real problem?

So if you've mostly eliminated that regression, then that's good
motivation for your patches.  (Though I think in addition to comparing
the patched and unpatched i_version case, we need to compare to the
unpatched not-i_version case.  I'm not clear whether you did that.)

--b.

> 
> --------------------8<------------------
> [global]
> direct=0
> size=2g
> filesize=512m
> bsrange=1-1
> timeout=60
> numjobs=1
> directory=/mnt/scratch
> 
> [f1]
> filename=randwrite
> rw=randwrite
> --------------------8<------------------
> 
> Unpatched kernel:
>   WRITE: io=7707KB, aggrb=128KB/s, minb=128KB/s, maxb=128KB/s, mint=60000msec, maxt=60000msec
> 
> Patched kernel:
>   WRITE: io=12701KB, aggrb=211KB/s, minb=211KB/s, maxb=211KB/s, mint=60000msec, maxt=60000msec
> 
> So quite a difference there and it's pretty consistent across runs. If I
> change the jobfile to have "direct=1" and "bsrange=4k-4k", then any
> variation between the two doesn't seem to be significant (numbers vary
> as much between runs on the same kernels and are roughly the same).
> 
> Playing with buffered I/O sizes between 1 byte and 4k shows that as the
> I/O sizes get larger, this makes less difference (which is what I'd
> expect).
> 
> Previous testing with ext4 shows roughly the same results. btrfs shows
> some benefit here but significantly less than with ext4 or xfs. Not sure
> why that is yet -- maybe CoW effects?
> 
> That said, I don't have a great test rig for this. I'm using VMs with a
> dedicated LVM volume that's on a random SSD I had laying around. It
> could use testing on a wider set of configurations and workloads.
> 
> I was also hoping that others may have workloads that they think might
> be (postively or negatively) affected by these changes. If you can think
> of any in particular, then I'm interested to hear about them.
> 
> -- 
> Jeff Layton <jlayton@redhat.com>
> --
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  reply	other threads:[~2017-03-20 21:44 UTC|newest]

Thread overview: 87+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-12-21 17:03 Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 01/30] lustre: don't set f_version in ll_readdir Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 02/30] ecryptfs: remove unnecessary i_version bump Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 03/30] ceph: remove the bump of i_version Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 04/30] f2fs: don't bother setting i_version Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 05/30] hpfs: don't bother with the i_version counter Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 06/30] jfs: remove initialization of " Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 07/30] nilfs2: remove inode->i_version initialization Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 08/30] orangefs: remove initialization of i_version Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 09/30] reiserfs: remove unneeded i_version bump Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 10/30] ntfs: remove i_version handling Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 11/30] fs: new API for handling i_version Jeff Layton
2017-03-03 22:36   ` J. Bruce Fields
2017-03-04  0:09     ` Jeff Layton
2017-03-03 23:55   ` NeilBrown
2017-03-04  1:58     ` Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 12/30] fat: convert to new i_version API Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 13/30] affs: " Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 14/30] afs: " Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 15/30] btrfs: " Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 16/30] exofs: switch " Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 17/30] ext2: convert " Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 18/30] ext4: " Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 19/30] nfs: " Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 20/30] nfsd: " Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 21/30] ocfs2: " Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 22/30] ufs: use " Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 23/30] xfs: convert to " Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 24/30] IMA: switch IMA over " Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 25/30] fs: add a "force" parameter to inode_inc_iversion Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 26/30] fs: only set S_VERSION when updating times if it has been queried Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 27/30] xfs: avoid setting XFS_ILOG_CORE if i_version doesn't need incrementing Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 28/30] btrfs: only dirty the inode in btrfs_update_time if something was changed Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 29/30] fs: track whether the i_version has been queried with an i_state flag Jeff Layton
2017-03-04  0:03   ` NeilBrown
2017-03-04  0:43     ` Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 30/30] fs: convert i_version counter over to an atomic64_t Jeff Layton
2016-12-22  8:38   ` Amir Goldstein
2016-12-22 13:27     ` Jeff Layton
2017-03-04  0:00   ` NeilBrown
2016-12-22  8:45 ` [RFC PATCH v1 00/30] fs: inode->i_version rework and optimization Christoph Hellwig
2016-12-22 14:42   ` Jeff Layton
2017-03-20 21:43     ` J. Bruce Fields [this message]
2017-03-21 13:45       ` Christoph Hellwig
2017-03-21 16:30         ` J. Bruce Fields
2017-03-21 17:23           ` Jeff Layton
2017-03-21 17:37             ` J. Bruce Fields
2017-03-21 17:51               ` J. Bruce Fields
2017-03-21 18:30             ` J. Bruce Fields
2017-03-21 18:46               ` Jeff Layton
2017-03-21 19:13                 ` J. Bruce Fields
2017-03-21 21:54                   ` Jeff Layton
2017-03-29 11:15                 ` Jan Kara
2017-03-29 17:54                   ` Jeff Layton
2017-03-29 23:41                     ` Dave Chinner
2017-03-30 11:24                       ` Jeff Layton
2017-04-04 18:38                       ` J. Bruce Fields
2017-03-30  6:47                     ` Jan Kara
2017-03-30 11:11                       ` Jeff Layton
2017-03-30 16:12                         ` J. Bruce Fields
2017-03-30 18:35                           ` Jeff Layton
2017-03-30 21:11                             ` Boaz Harrosh
2017-04-04 18:31                             ` J. Bruce Fields
2017-04-05  1:43                               ` NeilBrown
2017-04-05  8:05                                 ` Jan Kara
2017-04-05 18:14                                   ` J. Bruce Fields
2017-05-11 18:59                                     ` J. Bruce Fields
2017-05-11 22:22                                       ` NeilBrown
2017-05-12 16:21                                         ` J. Bruce Fields
2017-10-30 13:21                                           ` Jeff Layton
2017-05-12  8:27                                       ` Jan Kara
2017-05-12 15:56                                         ` J. Bruce Fields
2017-05-12 11:01                                       ` Jeff Layton
2017-05-12 15:57                                         ` J. Bruce Fields
2017-04-06  1:12                                   ` NeilBrown
2017-04-06  7:22                                     ` Jan Kara
2017-04-05 17:26                                 ` J. Bruce Fields
2017-04-01 23:05                           ` Dave Chinner
2017-04-03 14:00                             ` Jan Kara
2017-04-04 12:34                               ` Dave Chinner
2017-04-04 17:53                                 ` J. Bruce Fields
2017-04-05  1:26                                 ` NeilBrown
2017-03-21 21:45             ` Dave Chinner
2017-03-22 19:53               ` Jeff Layton
2017-03-03 23:00 ` J. Bruce Fields
2017-03-04  0:53   ` Jeff Layton
2017-03-08 17:29     ` J. Bruce Fields

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