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Date: Mon, 08 Aug 2011 15:46:33 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Wu Fengguang <fengguang.wu@...el.com>
Cc: linux-fsdevel@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>,
Jan Kara <jack@...e.cz>, Christoph Hellwig <hch@....de>,
Dave Chinner <david@...morbit.com>,
Greg Thelen <gthelen@...gle.com>,
Minchan Kim <minchan.kim@...il.com>,
Vivek Goyal <vgoyal@...hat.com>,
Andrea Righi <arighi@...eler.com>,
linux-mm <linux-mm@...ck.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/5] writeback: dirty position control
On Sat, 2011-08-06 at 16:44 +0800, Wu Fengguang wrote:
> +static unsigned long bdi_position_ratio(struct backing_dev_info *bdi,
> + unsigned long thresh,
> + unsigned long dirty,
> + unsigned long bdi_thresh,
> + unsigned long bdi_dirty)
> +{
> + unsigned long limit = hard_dirty_limit(thresh);
> + unsigned long origin;
> + unsigned long goal;
> + unsigned long long span;
> + unsigned long long pos_ratio; /* for scaling up/down the rate limit */
> +
> + if (unlikely(dirty >= limit))
> + return 0;
> +
> + /*
> + * global setpoint
> + */
> + goal = thresh - thresh / DIRTY_SCOPE;
> + origin = 4 * thresh;
> +
> + if (unlikely(origin < limit && dirty > (goal + origin) / 2)) {
> + origin = limit; /* auxiliary control line */
> + goal = (goal + origin) / 2;
> + pos_ratio >>= 1;
use before init?
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