From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH 3/7] writeback: introduce smoothed global dirty limit
Date: Sun, 19 Jun 2011 11:36:37 -0400
Message-ID: <20110619153636.GC20424@infradead.org>
References: <20110619150108.691351746@intel.com>
 <20110619150510.246140117@intel.com>
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Cc: "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	Jan Kara <jack@suse.cz>, Dave Chinner <david@fromorbit.com>,
	Christoph Hellwig <hch@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	LKML <linux-kernel@vger.kernel.org>
To: Wu Fengguang <fengguang.wu@intel.com>
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On Sun, Jun 19, 2011 at 11:01:11PM +0800, Wu Fengguang wrote:
> The start of a heavy weight application (ie. KVM) may instantly knock
> down determine_dirtyable_memory() and hence the global/bdi dirty
> thresholds.
> 
> So introduce global_dirty_limit for tracking the global dirty threshold
> with policies
> 
> - follow downwards slowly
> - follow up in one shot
> 
> global_dirty_limit can effectively mask out the impact of sudden drop of
> dirtyable memory. It will be used in the next patch for two new type of
> dirty limits.

This needs to be explained in more detail in comments near the actual
code.