From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752326Ab1HRXzU (ORCPT ); Thu, 18 Aug 2011 19:55:20 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:42128 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752098Ab1HRXzQ (ORCPT ); Thu, 18 Aug 2011 19:55:16 -0400 Date: Thu, 18 Aug 2011 16:54:28 -0700 From: Andrew Morton To: Mel Gorman Cc: Linux-MM , LKML , XFS , Dave Chinner , Christoph Hellwig , Johannes Weiner , Wu Fengguang , Jan Kara , Rik van Riel , Minchan Kim Subject: Re: [PATCH 6/7] mm: vmscan: Throttle reclaim if encountering too many dirty pages under writeback Message-Id: <20110818165428.4f01a1b9.akpm@linux-foundation.org> In-Reply-To: <1312973240-32576-7-git-send-email-mgorman@suse.de> References: <1312973240-32576-1-git-send-email-mgorman@suse.de> <1312973240-32576-7-git-send-email-mgorman@suse.de> X-Mailer: Sylpheed 3.0.2 (GTK+ 2.20.1; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 10 Aug 2011 11:47:19 +0100 Mel Gorman wrote: > The percentage that must be in writeback depends on the priority. At > default priority, all of them must be dirty. At DEF_PRIORITY-1, 50% > of them must be, DEF_PRIORITY-2, 25% etc. i.e. as pressure increases > the greater the likelihood the process will get throttled to allow > the flusher threads to make some progress. It'd be nice if the code comment were to capture this piece of implicit arithmetic. After all, it's a magic number and magic numbers should stick out like sore thumbs. And.. how do we know that the chosen magic numbers were optimal?