From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id 263BD6B0169 for ; Tue, 23 Aug 2011 23:16:09 -0400 (EDT) Date: Wed, 24 Aug 2011 11:16:03 +0800 From: Wu Fengguang Subject: Re: [PATCH 2/5] writeback: dirty position control Message-ID: <20110824031603.GA30873@localhost> References: <20110816022006.348714319@intel.com> <20110816022328.811348370@intel.com> <20110816194112.GA25517@quack.suse.cz> <20110817132347.GA6628@localhost> <20110817202414.GK9959@quack.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110817202414.GK9959@quack.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Jan Kara Cc: "linux-fsdevel@vger.kernel.org" , Peter Zijlstra , Andrew Morton , Christoph Hellwig , Dave Chinner , Greg Thelen , Minchan Kim , Vivek Goyal , Andrea Righi , linux-mm , LKML > > > > + x_intercept = setpoint + 2 * span; > ^^ BTW, why do you have 2*span here? It can result in x_intercept being > ~3*bdi_thresh... So maybe you should use bdi_thresh/2 in the computation of > span? OK, I'll follow your suggestion to use span = 8 * write_bw, for single bdi case span = bdi_thresh, for JBOD case x_intercept = setpoint + span; It does make sense to squeeze the bdi_dirty fluctuation range a bit by doubling span and making the control line more sharp. 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