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Date:   Wed, 5 Feb 2020 14:22:49 +0800
From:   Murphy Zhou <jencce.kernel@gmail.com>
To:     "J. Bruce Fields" <bfields@fieldses.org>
Cc:     "Darrick J. Wong" <darrick.wong@oracle.com>,
        Murphy Zhou <jencce.kernel@gmail.com>,
        linux-xfs@vger.kernel.org, linux-nfs@vger.kernel.org
Subject: Re: A NFS, xfs, reflink and rmapbt story
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 <20200124011019.GA8247@magnolia>
 <20200127223631.GA28982@fieldses.org>
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On Mon, Jan 27, 2020 at 05:36:31PM -0500, J. Bruce Fields wrote:
> On Thu, Jan 23, 2020 at 05:10:19PM -0800, Darrick J. Wong wrote:
> > On Thu, Jan 23, 2020 at 04:32:17PM +0800, Murphy Zhou wrote:
> > > Hi,
> > > 
> > > Deleting the files left by generic/175 costs too much time when testing
> > > on NFSv4.2 exporting xfs with rmapbt=1.
> > > 
> > > "./check -nfs generic/175 generic/176" should reproduce it.
> > > 
> > > My test bed is a 16c8G vm.
> > 
> > What kind of storage?
> > 
> > > NFSv4.2  rmapbt=1   24h+
> > 
> > <URK> Wow.  I wonder what about NFS makes us so slow now?  Synchronous
> > transactions on the inactivation?  (speculates wildly at the end of the
> > workday)
> > 
> > I'll have a look in the morning.  It might take me a while to remember
> > how to set up NFS42 :)
> 
> It may just be the default on a recent enough distro.
> 
> Though I'd be a little surprised if this behavior is specific to the
> protocol version.

This testcase requires reflink, which is only available in v4.2.
On other protocols, this testase does not run.

Murphy

> 
> nfsd_unlink() is basically just vfs_unlink() followed by
> commit_metadata().
> 
> --b.
> 
> > 
> > --D
> > 
> > > NFSv4.2  rmapbt=0   1h-2h
> > > xfs      rmapbt=1   10m+
> > > 
> > > At first I thought it hung, turns out it was just slow when deleting
> > > 2 massive reflined files.
> > > 
> > > It's reproducible using latest Linus tree, and Darrick's deferred-inactivation
> > > branch. Run latest for-next branch xfsprogs.
> > > 
> > > I'm not sure it's something wrong, just sharing with you guys. I don't
> > > remember I have identified this as a regression. It should be there for
> > > a long time.
> > > 
> > > Sending to xfs and nfs because it looks like all related. :)
> > > 
> > > This almost gets lost in my list. Not much information recorded, some
> > > trace-cmd outputs for your info. It's easy to reproduce. If it's
> > > interesting to you and need any info, feel free to ask.
> > > 
> > > Thanks,
> > > 
> > > 
> > > 7)   0.279 us    |  xfs_btree_get_block [xfs]();
> > > 7)   0.303 us    |  xfs_btree_rec_offset [xfs]();
> > > 7)   0.301 us    |  xfs_rmapbt_init_high_key_from_rec [xfs]();
> > > 7)   0.356 us    |  xfs_rmapbt_diff_two_keys [xfs]();
> > > 7)   0.305 us    |  xfs_rmapbt_init_key_from_rec [xfs]();
> > > 7)   0.306 us    |  xfs_rmapbt_diff_two_keys [xfs]();
> > > 7)               |  xfs_rmap_query_range_helper [xfs]() {
> > > 7)   0.279 us    |    xfs_rmap_btrec_to_irec [xfs]();
> > > 7)               |    xfs_rmap_lookup_le_range_helper [xfs]() {
> > > 1)   0.786 us    |  _raw_spin_lock_irqsave();
> > > 7)               |      /* xfs_rmap_lookup_le_range_candidate: dev 8:34 agno 2 agbno 6416 len 256 owner 67160161 offset 99284480 flags 0x0 */
> > > 7)   0.506 us    |    }
> > > 7)   1.680 us    |  }