linux-kernel - Re: [PATCH] improve the performance of large sequential write NFS workloads

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Date:	Wed, 6 Jan 2010 21:09:28 +0100
From:	Jan Kara <jack@...e.cz>
To:	Trond Myklebust <Trond.Myklebust@...app.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Wu Fengguang <fengguang.wu@...el.com>, Jan Kara <jack@...e.cz>,
	Steve Rago <sar@...-labs.com>,
	"linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"jens.axboe" <jens.axboe@...cle.com>,
	Peter Staubach <staubach@...hat.com>,
	Arjan van de Ven <arjan@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH] improve the performance of large sequential write NFS
 workloads

On Wed 06-01-10 14:53:14, Trond Myklebust wrote:
> ...and finally, this should convert the previous NFS patch to use the
> per-bdi accounting.
> 
> Cheers
>   Trond
> 
> -------------------------------------------------------------------------------------- 
> VM: Use per-bdi unstable accounting to improve use of wbc->force_commit
> 
> From: Trond Myklebust <Trond.Myklebust@...app.com>
> 
> Signed-off-by: Trond Myklebust <Trond.Myklebust@...app.com>
  I like this. You can add
Acked-by: Jan Kara <jack@...e.cz>
  to this patch previous patches adding unstable pages accounting.

								Honza
> ---
> 
>  mm/page-writeback.c |   13 +++++++------
>  1 files changed, 7 insertions(+), 6 deletions(-)
> 
> 
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index d90a0db..c537543 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -487,7 +487,6 @@ static void balance_dirty_pages(struct address_space *mapping,
>  {
>  	long nr_reclaimable, bdi_nr_reclaimable;
>  	long nr_writeback, bdi_nr_writeback;
> -	long nr_unstable_nfs;
>  	unsigned long background_thresh;
>  	unsigned long dirty_thresh;
>  	unsigned long bdi_thresh;
> @@ -504,18 +503,20 @@ static void balance_dirty_pages(struct address_space *mapping,
>  			.nr_to_write	= write_chunk,
>  			.range_cyclic	= 1,
>  		};
> +		long bdi_nr_unstable = 0;
>  
>  		get_dirty_limits(&background_thresh, &dirty_thresh,
>  				&bdi_thresh, bdi);
>  
> -		nr_unstable_nfs = global_page_state(NR_UNSTABLE_NFS);
>  		nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
> -					nr_unstable_nfs;
> +					global_page_state(NR_UNSTABLE_NFS);
>  		nr_writeback = global_page_state(NR_WRITEBACK);
>  
>  		bdi_nr_reclaimable = bdi_stat(bdi, BDI_DIRTY);
> -		if (bdi_cap_account_unstable(bdi))
> -			bdi_nr_reclaimable += bdi_stat(bdi, BDI_UNSTABLE);
> +		if (bdi_cap_account_unstable(bdi)) {
> +			bdi_nr_unstable = bdi_stat(bdi, BDI_UNSTABLE);
> +			bdi_nr_reclaimable += bdi_nr_unstable;
> +		}
>  		bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK);
>  
>  		if (bdi_nr_reclaimable + bdi_nr_writeback <= bdi_thresh)
> @@ -545,7 +546,7 @@ static void balance_dirty_pages(struct address_space *mapping,
>  		if (bdi_nr_reclaimable > bdi_thresh) {
>  			wbc.force_commit = 0;
>  			/* Force NFS to also free up unstable writes. */
> -			if (nr_unstable_nfs > nr_reclaimable / 2)
> +			if (bdi_nr_unstable > bdi_nr_reclaimable / 2)
>  				wbc.force_commit = 1;
>  
>  			writeback_inodes_wbc(&wbc);
> 
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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