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Date:   Fri, 12 Jun 2020 22:35:33 -0700
From:   "Darrick J. Wong" <darrick.wong@oracle.com>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     "Darrick J. Wong" <djwong@kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        linux-xfs <linux-xfs@vger.kernel.org>,
        Dave Chinner <david@fromorbit.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Eric Sandeen <sandeen@sandeen.net>,
        Christoph Hellwig <hch@lst.de>
Subject: Re: [GIT PULL] xfs: new code for 5.8 (now with fixed To line)
Message-ID: <20200613053533.GJ11245@magnolia>
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On Tue, Jun 02, 2020 at 07:40:35PM -0700, Linus Torvalds wrote:
> On Tue, Jun 2, 2020 at 9:26 AM Darrick J. Wong <djwong@kernel.org> wrote:
> >
> > fs/xfs/xfs_log_recover.c                           | 2561 ++------------------
> >  102 files changed, 4244 insertions(+), 4817 deletions(-)
> 
> Interestingly, the changes to that xfs_log_recover.c file really seem
> to break the default git diff algorithm (the linear-space Myers'
> algorithm)
> 
> The default settings give me
> 
>  fs/xfs/xfs_log_recover.c                           | 2801 ++------------------
>  102 files changed, 4366 insertions(+), 4939 deletions(-)
> 
> which is not very close to yours. With the extra effort "--minimal" I get
> 
>  fs/xfs/xfs_log_recover.c                           | 2561 ++------------------
>  102 files changed, 4246 insertions(+), 4819 deletions(-)
> 
> but based on your output, I suspect you used "--patience", which gives that
> 
>  fs/xfs/xfs_log_recover.c                           | 2561 ++------------------
>  102 files changed, 4244 insertions(+), 4817 deletions(-)
> 
> output (the difference there wrt minimal came from
> fs/xfs/libxfs/xfs_symlink_remote.c).
> 
> I'm used to seeing small differences in the line counts due to
> different diff heuristics, but that 250 line difference for
> "--patience" is more than you usually get.
> 
> None of this matters, and I'm not at all suggesting you change any of
> your workflow.

<nod> One of the XFS developers suggested I experiment with --patience
to see if it would make the diff output a little less eager to minimize
the changed lines even at the expense of reviewability.  The outcome is
mostly identical, but there were a few places where using it really did
help to try to keep basic code blocks together.

--D

> I'm just commenting because I was going "why am I not getting a
> matching diffstat", and while I'm used to seeing small differences
> from diff algorithms, that 240 line-count change was really a lot more
> than I normally encounter.
> 
>                       Linus
>