Re: [PATCH 11/11] xfs: skip flushing log items during push

["Darrick J. Wong" <djwong@kernel.org>]

On Fri, Jun 21, 2024 at 07:48:08AM +0200, Christoph Hellwig wrote:
> On Thu, Jun 20, 2024 at 12:51:42PM -0700, Darrick J. Wong wrote:
> > > Further with no backoff we don't need to gather huge delwri lists to
> > > mitigate the impact of backoffs, so we can submit IO more frequently
> > > and reduce the time log items spend in flushing state by breaking
> > > out of the item push loop once we've gathered enough IO to batch
> > > submission effectively.
> > 
> > Is that what the new count > 1000 branch does?
> 
> That's my interpreation anyway.  I'll let Dave chime in if he disagrees.

<nod> I'll await a response on this...

> > 
> > > Signed-off-by: Dave Chinner <dchinner@redhat.com>
> > > ---
> > >  fs/xfs/xfs_inode.c      | 1 +
> > >  fs/xfs/xfs_inode_item.c | 6 +++++-
> > 
> > Does it make sense to do this for buffer or dquot items too?
> 
> Not having written this here is my 2 unqualified cents:
> 
> For dquots it looks like it could be easily ported over, but I guess no
> one has been bothering with dquot performance work for a while as it's
> also missing a bunch of other things we did to the inode.  But given that
> according to Dave's commit log the іnode cluster flushing is a big part
> of this dquots probably aren't as affected anyway as we flush them
> individually (and there generally are a lot fewer dquot items in the AIL
> anyway).

It probably helps that dquot "clusters" are also single fsblocks too.

> For buf items the buffers are queued up on the on-stack delwri list
> and written when we flush them.  So we won't ever find already
> flushing items.

Oh right, because only the AIL flushes logged buffers to disk.

--D