Re: [PATCH 07/10] xfs: only free posteof blocks on first close

Darrick J. Wong
2024-06-24T16:49:47Z

On Mon, Jun 24, 2024 at 06:08:23PM +0200, Christoph Hellwig wrote:
> On Mon, Jun 24, 2024 at 08:46:21AM -0700, Darrick J. Wong wrote:
> > On Sun, Jun 23, 2024 at 07:34:52AM +0200, Christoph Hellwig wrote:
> > > From: "Darrick J. Wong" <djwong@kernel.org>
> > >
> > > Certain workloads fragment files on XFS very badly, such as a software
> > > package that creates a number of threads, each of which repeatedly run
> > > the sequence: open a file, perform a synchronous write, and close the
> > > file, which defeats the speculative preallocation mechanism. We work
> > > around this problem by only deleting posteof blocks the /first/ time a
> > > file is closed to preserve the behavior that unpacking a tarball lays
> > > out files one after the other with no gaps.
> > >
> > > Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> > > [hch: rebased, updated comment, renamed the flag]
> > > Signed-off-by: Christoph Hellwig <hch@lst.de>
> >
> > Someone please review this? The last person to try was Dave, five years
> > ago, and I do not know if he ever saw what it did to various workloads.
> >
> > https://lore.kernel.org/linux-xfs/20190315034237.GL23020@dastard/
>
> Well, the read-only check Dave suggested is in the previous patch,
> and the tests he sent cover the relevant synthetic workloads. What
> else are you looking for?

Nothing -- it looks fine to me, but as it's authored by me, I can't
meaningfully slap an RVB tag on it, can I?

Eh I've done the rest of the series; let's try it anyway:
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D