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Subject: Re: [PATCH 06/13] writeback: bdi write bandwidth estimation
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Wu Fengguang <fengguang.wu@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, Jan Kara <jack@suse.cz>,
        Li Shaohua <shaohua.li@intel.com>, Christoph Hellwig <hch@lst.de>,
        Dave Chinner <david@fromorbit.com>, "Theodore Ts'o" <tytso@mit.edu>,
        Chris Mason <chris.mason@oracle.com>, Mel Gorman <mel@csn.ul.ie>,
        Rik van Riel <riel@redhat.com>,
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	 <20101117042850.002299964@intel.com>
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Date: Wed, 24 Nov 2010 11:58:22 +0100
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On Wed, 2010-11-17 at 12:27 +0800, Wu Fengguang wrote:

> @@ -555,8 +592,10 @@ static void balance_dirty_pages(struct a
>  		pause = clamp_val(pause, 1, HZ/10);
>  
>  pause:
> +		bdi_update_write_bandwidth(bdi, &bw_time, &bw_written);
>  		__set_current_state(TASK_INTERRUPTIBLE);
>  		io_schedule_timeout(pause);
> +		bdi_update_write_bandwidth(bdi, &bw_time, &bw_written);
>  
>  		/*
>  		 * The bdi thresh is somehow "soft" limit derived from the

So its really a two part bandwidth calculation, the first call is:

  bdi_get_bandwidth()

and the second call is:

  bdi_update_bandwidth()

Would it make sense to actually implement it with two functions instead
of overloading the functionality of the one function?