From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 10 Nov 2008 13:12:55 -0800 From: Andrew Morton Subject: Re: [PATCH -mm] mm: fine-grained dirty_ratio_pcm and dirty_background_ratio_pcm (v2) Message-Id: <20081110131255.ce71ce60.akpm@linux-foundation.org> In-Reply-To: <4918A074.1050003@gmail.com> References: <1221232192-13553-1-git-send-email-righi.andrea@gmail.com> <20080912131816.e0cfac7a.akpm@linux-foundation.org> <532480950809221641y3471267esff82a14be8056586@mail.gmail.com> <48EB4236.1060100@linux.vnet.ibm.com> <48EB851D.2030300@gmail.com> <20081008101642.fcfb9186.kamezawa.hiroyu@jp.fujitsu.com> <48ECB215.4040409@linux.vnet.ibm.com> <48EE236A.90007@gmail.com> <4918A074.1050003@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: righi.andrea@gmail.com Cc: kamezawa.hiroyu@jp.fujitsu.com, rientjes@google.com, balbir@linux.vnet.ibm.com, mrubin@google.com, menage@google.com, dave@linux.vnet.ibm.com, chlunde@ping.uio.no, dpshah@google.com, eric.rannaud@gmail.com, fernando@oss.ntt.co.jp, agk@sourceware.org, m.innocenti@cineca.it, s-uchida@ap.jp.nec.com, ryov@valinux.co.jp, matt@bluehost.com, dradford@bluehost.com, kosaki.motohiro@jp.fujitsu.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, containers@lists.osdl.org List-ID: On Mon, 10 Nov 2008 21:58:28 +0100 Andrea Righi wrote: > The current granularity of 5% of dirtyable memory for dirty pages writeback is > too coarse for large memory machines and this will get worse as > memory-size/disk-speed ratio continues to increase. > > These large writebacks can be unpleasant for desktop or latency-sensitive > environments, where the time to complete each writeback can be perceived as a > lack of responsiveness by the whole system. > > Following there's a similar solution as discussed in [1], but a little > bit simplified in order to provide the same functionality (in particular > to avoid backward compatibility problems) and reduce the amount of code > needed to implement an in-kernel parser to handle percentages with > decimals digits. > > The kernel provides the following parameters: > - dirty_ratio, dirty_background_ratio in percentage (1 ... 100) > - dirty_ratio_pcm, dirty_background_ratio_pcm in units of percent mille (1 ... 100,000) hm, so how long until dirty_ratio_pcm becomes too coarse... What happened to the idea of specifying these in units of kilobytes? -- 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