linux-kernel - Re: [PATCH 7/9] writeback: periodically trim the writeback list

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Date:	Mon, 16 Mar 2015 12:43:37 +0100
From:	Jan Kara <jack@...e.cz>
To:	Josef Bacik <jbacik@...com>
Cc:	linux-fsdevel@...r.kernel.org, david@...morbit.com,
	viro@...iv.linux.org.uk, jack@...e.cz,
	linux-kernel@...r.kernel.org, Dave Chinner <dchinner@...hat.com>
Subject: Re: [PATCH 7/9] writeback: periodically trim the writeback list

On Mon 16-03-15 11:16:08, Jan Kara wrote:
> On Tue 10-03-15 15:45:22, Josef Bacik wrote:
> > From: Dave Chinner <dchinner@...hat.com>
> > 
> > Inodes are removed lazily from the bdi writeback list, so in the
> > absence of sync(2) work inodes will build up on the bdi writback
> > list even though they are no longer under IO. Use the periodic
> > kupdate work check to remove inodes no longer under IO from the
> > writeback list.
> > 
> > Signed-off-by: Dave Chinner <dchinner@...hat.com>
>   Looks good. You can add:
> Reviewed-by: Jan Kara <jack@...e.cz>
  BTW, it would be nice to add here some numbers showing how sync was
speeded up with the last two patches. The change makes a lot of sense but
it would be nice as a sanity check...

								Honza

> > ---
> >  fs/fs-writeback.c | 19 +++++++++++++++++++
> >  1 file changed, 19 insertions(+)
> > 
> > diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
> > index 82b0f43..aa0de0f 100644
> > --- a/fs/fs-writeback.c
> > +++ b/fs/fs-writeback.c
> > @@ -1037,6 +1037,23 @@ static long wb_check_background_flush(struct bdi_writeback *wb)
> >  	return 0;
> >  }
> >  
> > +/*
> > + * clean out writeback list for all inodes that don't have IO in progress
> > + */
> > +static void wb_trim_writeback_list(struct bdi_writeback *wb)
> > +{
> > +	struct inode *inode;
> > +	struct inode *tmp;
> > +
> > +	spin_lock(&wb->list_lock);
> > +	list_for_each_entry_safe(inode, tmp, &wb->b_writeback, i_wb_list) {
> > +		if (!mapping_tagged(inode->i_mapping, PAGECACHE_TAG_WRITEBACK))
> > +			list_del_init(&inode->i_wb_list);
> > +	}
> > +	spin_unlock(&wb->list_lock);
> > +
> > +}
> > +
> >  static long wb_check_old_data_flush(struct bdi_writeback *wb)
> >  {
> >  	unsigned long expired;
> > @@ -1053,6 +1070,8 @@ static long wb_check_old_data_flush(struct bdi_writeback *wb)
> >  	if (time_before(jiffies, expired))
> >  		return 0;
> >  
> > +	wb_trim_writeback_list(wb);
> > +
> >  	wb->last_old_flush = jiffies;
> >  	nr_pages = get_nr_dirty_pages();
> >  
> > -- 
> > 1.9.3
> > 
> -- 
> Jan Kara <jack@...e.cz>
> SUSE Labs, CR
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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