From mboxrd@z Thu Jan 1 00:00:00 1970 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <18151.20356.862163.430265@stoffel.org> Date: Tue, 11 Sep 2007 22:31:32 -0400 From: "John Stoffel" Subject: Re: [PATCH 00/23] per device dirty throttling -v10 In-Reply-To: <20070911195350.825778000@chello.nl> References: <20070911195350.825778000@chello.nl> Sender: owner-linux-mm@kvack.org Return-Path: To: Peter Zijlstra Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, miklos@szeredi.hu, akpm@linux-foundation.org, neilb@suse.de, dgc@sgi.com, tomoki.sekiyama.qu@hitachi.com, nikita@clusterfs.com, trond.myklebust@fys.uio.no, yingchao.zhou@gmail.com, richard@rsk.demon.co.uk, torvalds@linux-foundation.org List-ID: Peter> Per device dirty throttling patches These patches aim to Peter> improve balance_dirty_pages() and directly address three Peter> issues: Peter> 1) inter device starvation Peter> 2) stacked device deadlocks Peter> 3) inter process starvation Peter> 1 and 2 are a direct result from removing the global dirty Peter> limit and using per device dirty limits. By giving each device Peter> its own dirty limit is will no longer starve another device, Peter> and the cyclic dependancy on the dirty limit is broken. Ye haa! This should be a big improvement. Peter> In order to efficiently distribute the dirty limit across the Peter> independant devices a floating proportion is used, this will Peter> allocate a share of the total limit proportional to the Peter> device's recent activity. I'm not sure I like or agree with this. Shouldn't we be limiting based on the device's capability to sustain traffic? So if I have a RAID device which can read/write a total of 100Mb/sec, while at the same time I've got a CF device which can do 5Mb/sec, shouldn't we be more strongly limiting the CF device, even if it is the only device being written to? Of course, I haven't read the patches yet, nor am I qualified to comment on them in any meanginful way I think. Hopefully I'm just missing something key here in the explanation. Peter> 3 is done by also scaling the dirty limit proportional to the Peter> current task's recent dirty rate. Do you mean task or device here? I'm just wondering how well this works with a bunch of devices with wildly varying speeds. John -- 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/ . Don't email: email@kvack.org