From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wu Fengguang Subject: Re: [PATCH 2/5] writeback: dirty position control Date: Tue, 9 Aug 2011 06:47:42 +0800 Message-ID: <20110808224742.GB7176@localhost> References: <20110806084447.388624428@intel.com> <20110806094526.733282037@intel.com> <1312811193.10488.33.camel@twins> <20110808141128.GA22080@localhost> <1312813909.10488.38.camel@twins> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "linux-fsdevel@vger.kernel.org" , Andrew Morton , Jan Kara , Christoph Hellwig , Dave Chinner , Greg Thelen , Minchan Kim , Vivek Goyal , Andrea Righi , linux-mm , LKML To: Peter Zijlstra Return-path: Content-Disposition: inline In-Reply-To: <1312813909.10488.38.camel@twins> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org On Mon, Aug 08, 2011 at 10:31:49PM +0800, Peter Zijlstra wrote: > On Mon, 2011-08-08 at 22:11 +0800, Wu Fengguang wrote: > > It's actually dead code because (origin < limit) should never happen. > > I feel so good being able to drop 5 more lines of code :) > > OK, but that leaves me trying to figure out what origin is, and why its > 4 * thresh. origin is where the control line crosses the X axis (in both the global/bdi setpoint cases). "4 * thresh" is merely something larger than max(dirty, thresh) that yields reasonably gentle slope. The more slope, the larger "gravity" to bring the dirty pages back to the setpoint. > I'm having a horrible time understanding this stuff. Sorry for that. Do you have more questions? Thanks, Fengguang -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org