linux-kernel - Re: [PATCH 5/7] btrfs: fix dirtied pages accounting on sub-page writes

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Date:	Mon, 28 Nov 2011 22:16:07 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	Chris Mason <chris.mason@...cle.com>
Cc:	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	Jan Kara <jack@...e.cz>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Christoph Hellwig <hch@....de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/7] btrfs: fix dirtied pages accounting on sub-page
 writes

Hi Chris,

This btrfs patch depends on the account_page_redirty() introduced
earlier in this series.

Shall I carry it together with this patchset?

Thanks,
Fengguang

On Mon, Nov 28, 2011 at 09:53:43PM +0800, Wu, Fengguang wrote:
> When doing 1KB sequential writes to the same page,
> balance_dirty_pages_ratelimited_nr() should be called once instead of 4
> times, the latter makes the dirtier tasks be throttled much too heavy.
> 
> Fix it with proper de-accounting on clear_page_dirty_for_io().
> 
> CC: Chris Mason <chris.mason@...cle.com>
> Signed-off-by: Wu Fengguang <fengguang.wu@...el.com>
> ---
>  fs/btrfs/file.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> --- linux-next.orig/fs/btrfs/file.c	2011-11-17 20:13:47.000000000 +0800
> +++ linux-next/fs/btrfs/file.c	2011-11-17 20:18:51.000000000 +0800
> @@ -1136,7 +1136,8 @@ again:
>  				     GFP_NOFS);
>  	}
>  	for (i = 0; i < num_pages; i++) {
> -		clear_page_dirty_for_io(pages[i]);
> +		if (clear_page_dirty_for_io(pages[i]))
> +			account_page_redirty(pages[i]);
>  		set_page_extent_mapped(pages[i]);
>  		WARN_ON(!PageLocked(pages[i]));
>  	}
> 
--
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