linux-kernel - Re: [PATCH 5/9] writeback: consolidate variable names in balance_dirty

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Date:	Thu, 30 Jun 2011 19:26:45 +0200
From:	Jan Kara <jack@...e.cz>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	linux-fsdevel@...r.kernel.org, Jan Kara <jack@...e.cz>,
	Dave Chinner <david@...morbit.com>,
	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/9] writeback: consolidate variable names in
 balance_dirty_pages()

On Wed 29-06-11 22:52:50, Wu Fengguang wrote:
> Introduce
> 
> 	nr_dirty = NR_FILE_DIRTY + NR_WRITEBACK + NR_UNSTABLE_NFS
> 
> in order to simplify many tests in the following patches.
> 
> balance_dirty_pages() will eventually care only about the dirty sums
> besides nr_writeback.
  Looks OK.
Acked-by: Jan Kara <jack@...e.cz>

								Honza
> 
> Signed-off-by: Wu Fengguang <fengguang.wu@...el.com>
> ---
>  mm/page-writeback.c |   21 +++++++++++----------
>  1 file changed, 11 insertions(+), 10 deletions(-)
> 
> --- linux-next.orig/mm/page-writeback.c	2011-06-20 00:16:58.000000000 +0800
> +++ linux-next/mm/page-writeback.c	2011-06-20 00:17:06.000000000 +0800
> @@ -560,8 +560,9 @@ static void bdi_update_bandwidth(struct 
>  static void balance_dirty_pages(struct address_space *mapping,
>  				unsigned long write_chunk)
>  {
> -	long nr_reclaimable, bdi_nr_reclaimable;
> -	long nr_writeback, bdi_nr_writeback;
> +	unsigned long nr_reclaimable, bdi_nr_reclaimable;
> +	unsigned long nr_dirty;  /* = file_dirty + writeback + unstable_nfs */
> +	unsigned long bdi_dirty;
>  	unsigned long background_thresh;
>  	unsigned long dirty_thresh;
>  	unsigned long bdi_thresh;
> @@ -574,7 +575,7 @@ static void balance_dirty_pages(struct a
>  	for (;;) {
>  		nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
>  					global_page_state(NR_UNSTABLE_NFS);
> -		nr_writeback = global_page_state(NR_WRITEBACK);
> +		nr_dirty = nr_reclaimable + global_page_state(NR_WRITEBACK);
>  
>  		global_dirty_limits(&background_thresh, &dirty_thresh);
>  
> @@ -583,8 +584,7 @@ static void balance_dirty_pages(struct a
>  		 * catch-up. This avoids (excessively) small writeouts
>  		 * when the bdi limits are ramping up.
>  		 */
> -		if (nr_reclaimable + nr_writeback <=
> -				(background_thresh + dirty_thresh) / 2)
> +		if (nr_dirty <= (background_thresh + dirty_thresh) / 2)
>  			break;
>  
>  		bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
> @@ -602,10 +602,12 @@ static void balance_dirty_pages(struct a
>  		 */
>  		if (bdi_thresh < 2*bdi_stat_error(bdi)) {
>  			bdi_nr_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE);
> -			bdi_nr_writeback = bdi_stat_sum(bdi, BDI_WRITEBACK);
> +			bdi_dirty = bdi_nr_reclaimable +
> +				    bdi_stat_sum(bdi, BDI_WRITEBACK);
>  		} else {
>  			bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE);
> -			bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK);
> +			bdi_dirty = bdi_nr_reclaimable +
> +				    bdi_stat(bdi, BDI_WRITEBACK);
>  		}
>  
>  		/*
> @@ -614,9 +616,8 @@ static void balance_dirty_pages(struct a
>  		 * bdi or process from holding back light ones; The latter is
>  		 * the last resort safeguard.
>  		 */
> -		dirty_exceeded =
> -			(bdi_nr_reclaimable + bdi_nr_writeback > bdi_thresh)
> -			|| (nr_reclaimable + nr_writeback > dirty_thresh);
> +		dirty_exceeded = (bdi_dirty > bdi_thresh) ||
> +				  (nr_dirty > dirty_thresh);
>  
>  		if (!dirty_exceeded)
>  			break;
> 
> 
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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