Re: [PATCH 01/13] xfs: optimize _btree_query_all

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Tue, Jun 06, 2017 at 09:32:42AM -0400, Brian Foster wrote:
> On Fri, Jun 02, 2017 at 02:24:06PM -0700, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@oracle.com>
> > 
> > Don't bother wandering our way through the leaf nodes when the caller
> > issues a query_all; just zoom down the left side of the tree and walk
> > rightwards along level zero.
> > 
> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > ---
> >  fs/xfs/libxfs/xfs_btree.c |   44 +++++++++++++++++++++++++++++++++++++++-----
> >  1 file changed, 39 insertions(+), 5 deletions(-)
> > 
> > 
> > diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c
> > index 3a673ba..07d75bc 100644
> > --- a/fs/xfs/libxfs/xfs_btree.c
> > +++ b/fs/xfs/libxfs/xfs_btree.c
> > @@ -4849,12 +4849,46 @@ xfs_btree_query_all(
> >  	xfs_btree_query_range_fn	fn,
> >  	void				*priv)
> >  {
> > -	union xfs_btree_irec		low_rec;
> > -	union xfs_btree_irec		high_rec;
> > +	union xfs_btree_rec		*recp;
> > +	int				stat;
> > +	int				error;
> > +
> > +	/*
> > +	 * Find the leftmost record.  The btree cursor must be set
> > +	 * to the low record used to generate low_key.
> > +	 */
> > +	memset(&cur->bc_rec, 0, sizeof(cur->bc_rec));
> > +	stat = 0;
> > +	error = xfs_btree_lookup(cur, XFS_LOOKUP_LE, &stat);
> > +	if (error)
> > +		goto out;
> > +
> > +	/* Nothing?  See if there's anything to the right. */
> > +	if (!stat) {
> > +		error = xfs_btree_increment(cur, 0, &stat);
> > +		if (error)
> > +			goto out;
> > +	}
> >  
> > -	memset(&low_rec, 0, sizeof(low_rec));
> > -	memset(&high_rec, 0xFF, sizeof(high_rec));
> > -	return xfs_btree_query_range(cur, &low_rec, &high_rec, fn, priv);
> > +	while (stat) {
> > +		/* Find the record. */
> > +		error = xfs_btree_get_rec(cur, &recp, &stat);
> > +		if (error || !stat)
> > +			break;
> > +
> > +		/* Callback */
> > +		error = fn(cur, recp, priv);
> > +		if (error < 0 || error == XFS_BTREE_QUERY_RANGE_ABORT)
> > +			break;
> > +
> > +		/* Move on to the next record. */
> > +		error = xfs_btree_increment(cur, 0, &stat);
> > +		if (error)
> > +			break;
> > +	}
> > +
> > +out:
> > +	return error;
> 
> This all looks quite similar to xfs_btree_simple_query_range(), minus
> the associated key checks. I doubt the latter measurably affects the
> performance of a btree walk. Could we call that function directly here?

Yes, we could.  Will fix and resend.

--D

> 
> Brian
> 
> >  }
> >  
> >  /*
> > 
> > --
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