Re: [PATCH 1/3] xfs: add debug knobs to control btree bulk load slack factors

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

On Fri, Oct 25, 2019 at 10:19:47AM -0400, Brian Foster wrote:
> On Wed, Oct 09, 2019 at 09:49:53AM -0700, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@oracle.com>
> > 
> > Add some debug knobs so that we can control the leaf and node block
> > slack when rebuilding btrees.
> > 
> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > ---
> >  fs/xfs/xfs_globals.c |    6 ++++++
> >  fs/xfs/xfs_sysctl.h  |    2 ++
> >  fs/xfs/xfs_sysfs.c   |   54 ++++++++++++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 62 insertions(+)
> > 
> > 
> > diff --git a/fs/xfs/xfs_globals.c b/fs/xfs/xfs_globals.c
> > index fa55ab8b8d80..8f67027c144b 100644
> > --- a/fs/xfs/xfs_globals.c
> > +++ b/fs/xfs/xfs_globals.c
> > @@ -43,4 +43,10 @@ struct xfs_globals xfs_globals = {
> >  #ifdef DEBUG
> >  	.pwork_threads		=	-1,	/* automatic thread detection */
> >  #endif
> > +
> > +	/* Bulk load new btree leaf blocks to 75% full. */
> > +	.bload_leaf_slack	=	-1,
> > +
> > +	/* Bulk load new btree node blocks to 75% full. */
> > +	.bload_node_slack	=	-1,
> 
> What are the units for these fields?

Records (or key/ptr pairs).

> Seems reasonable outside of that, though I'd probably reorder it to
> after the related code such that this patch also includes whatever
> bits that actually use the fields.

It's the next patch.  Will reorder.

Thanks for reviewing!  I totally replied to these in reverse redro! :)

--D

> Brian
> 
> >  };
> > diff --git a/fs/xfs/xfs_sysctl.h b/fs/xfs/xfs_sysctl.h
> > index 8abf4640f1d5..aecccceee4ca 100644
> > --- a/fs/xfs/xfs_sysctl.h
> > +++ b/fs/xfs/xfs_sysctl.h
> > @@ -85,6 +85,8 @@ struct xfs_globals {
> >  #ifdef DEBUG
> >  	int	pwork_threads;		/* parallel workqueue threads */
> >  #endif
> > +	int	bload_leaf_slack;	/* btree bulk load leaf slack */
> > +	int	bload_node_slack;	/* btree bulk load node slack */
> >  	int	log_recovery_delay;	/* log recovery delay (secs) */
> >  	int	mount_delay;		/* mount setup delay (secs) */
> >  	bool	bug_on_assert;		/* BUG() the kernel on assert failure */
> > diff --git a/fs/xfs/xfs_sysfs.c b/fs/xfs/xfs_sysfs.c
> > index f1bc88f4367c..673ad21a9585 100644
> > --- a/fs/xfs/xfs_sysfs.c
> > +++ b/fs/xfs/xfs_sysfs.c
> > @@ -228,6 +228,58 @@ pwork_threads_show(
> >  XFS_SYSFS_ATTR_RW(pwork_threads);
> >  #endif /* DEBUG */
> >  
> > +STATIC ssize_t
> > +bload_leaf_slack_store(
> > +	struct kobject	*kobject,
> > +	const char	*buf,
> > +	size_t		count)
> > +{
> > +	int		ret;
> > +	int		val;
> > +
> > +	ret = kstrtoint(buf, 0, &val);
> > +	if (ret)
> > +		return ret;
> > +
> > +	xfs_globals.bload_leaf_slack = val;
> > +	return count;
> > +}
> > +
> > +STATIC ssize_t
> > +bload_leaf_slack_show(
> > +	struct kobject	*kobject,
> > +	char		*buf)
> > +{
> > +	return snprintf(buf, PAGE_SIZE, "%d\n", xfs_globals.bload_leaf_slack);
> > +}
> > +XFS_SYSFS_ATTR_RW(bload_leaf_slack);
> > +
> > +STATIC ssize_t
> > +bload_node_slack_store(
> > +	struct kobject	*kobject,
> > +	const char	*buf,
> > +	size_t		count)
> > +{
> > +	int		ret;
> > +	int		val;
> > +
> > +	ret = kstrtoint(buf, 0, &val);
> > +	if (ret)
> > +		return ret;
> > +
> > +	xfs_globals.bload_node_slack = val;
> > +	return count;
> > +}
> > +
> > +STATIC ssize_t
> > +bload_node_slack_show(
> > +	struct kobject	*kobject,
> > +	char		*buf)
> > +{
> > +	return snprintf(buf, PAGE_SIZE, "%d\n", xfs_globals.bload_node_slack);
> > +}
> > +XFS_SYSFS_ATTR_RW(bload_node_slack);
> > +
> >  static struct attribute *xfs_dbg_attrs[] = {
> >  	ATTR_LIST(bug_on_assert),
> >  	ATTR_LIST(log_recovery_delay),
> > @@ -236,6 +288,8 @@ static struct attribute *xfs_dbg_attrs[] = {
> >  #ifdef DEBUG
> >  	ATTR_LIST(pwork_threads),
> >  #endif
> > +	ATTR_LIST(bload_leaf_slack),
> > +	ATTR_LIST(bload_node_slack),
> >  	NULL,
> >  };
> >  
> > 
>