From: Dave Chinner <david@fromorbit.com>
To: Avi Kivity <avi@scylladb.com>
Cc: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
andres@anarazel.de
Subject: Re: [RFC] xfs: reduce sub-block DIO serialisation
Date: Wed, 13 Jan 2021 09:13:24 +1100 [thread overview]
Message-ID: <20210112221324.GU331610@dread.disaster.area> (raw)
In-Reply-To: <32f99253-fe56-9198-e47c-7eb0e24fdf73@scylladb.com>
On Tue, Jan 12, 2021 at 10:01:35AM +0200, Avi Kivity wrote:
> On 1/12/21 3:07 AM, Dave Chinner wrote:
> > Hi folks,
> >
> > This is the XFS implementation on the sub-block DIO optimisations
> > for written extents that I've mentioned on #xfs and a couple of
> > times now on the XFS mailing list.
> >
> > It takes the approach of using the IOMAP_NOWAIT non-blocking
> > IO submission infrastructure to optimistically dispatch sub-block
> > DIO without exclusive locking. If the extent mapping callback
> > decides that it can't do the unaligned IO without extent
> > manipulation, sub-block zeroing, blocking or splitting the IO into
> > multiple parts, it aborts the IO with -EAGAIN. This allows the high
> > level filesystem code to then take exclusive locks and resubmit the
> > IO once it has guaranteed no other IO is in progress on the inode
> > (the current implementation).
>
>
> Can you expand on the no-splitting requirement? Does it involve only
> splitting by XFS (IO spans >1 extents) or lower layers (RAID)?
XFS only.
> The reason I'm concerned is that it's the constraint that the application
> has least control over. I guess I could use RWF_NOWAIT to avoid blocking my
> main thread (but last time I tried I'd get occasional EIOs that frightened
> me off that).
Spurious EIO from RWF_NOWAIT is a bug that needs to be fixed. DO you
have any details?
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
next prev parent reply other threads:[~2021-01-12 22:36 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-12 1:07 [RFC] xfs: reduce sub-block DIO serialisation Dave Chinner
2021-01-12 1:07 ` [PATCH 1/6] iomap: convert iomap_dio_rw() to an args structure Dave Chinner
2021-01-12 1:22 ` Damien Le Moal
2021-01-12 1:40 ` Darrick J. Wong
2021-01-12 1:53 ` Dave Chinner
2021-01-12 10:31 ` Christoph Hellwig
2021-01-12 1:07 ` [PATCH 2/6] iomap: move DIO NOWAIT setup up into filesystems Dave Chinner
2021-01-12 1:07 ` [PATCH 3/6] xfs: factor out a xfs_ilock_iocb helper Dave Chinner
2021-01-12 1:07 ` [PATCH 4/6] xfs: make xfs_file_aio_write_checks IOCB_NOWAIT-aware Dave Chinner
2021-01-12 1:07 ` [PATCH 5/6] xfs: split unaligned DIO write code out Dave Chinner
2021-01-12 10:37 ` Christoph Hellwig
2021-01-12 1:07 ` [PATCH 6/6] xfs: reduce exclusive locking on unaligned dio Dave Chinner
2021-01-12 10:42 ` Christoph Hellwig
2021-01-12 17:01 ` Brian Foster
2021-01-12 17:10 ` Christoph Hellwig
2021-01-12 22:06 ` Dave Chinner
2021-01-12 8:01 ` [RFC] xfs: reduce sub-block DIO serialisation Avi Kivity
2021-01-12 22:13 ` Dave Chinner [this message]
2021-01-13 8:00 ` Avi Kivity
2021-01-13 20:38 ` Dave Chinner
2021-01-14 6:48 ` Avi Kivity
2021-01-17 21:34 ` Dave Chinner
2021-01-18 7:41 ` Avi Kivity
[not found] ` <CACz=WechdgSnVHQsg0LKjMiG8kHLujBshmc270yrdjxfpffmDQ@mail.gmail.com>
2021-01-17 21:36 ` Dave Chinner
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