From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with SMTP id 60A206B024D for ; Sun, 25 Jul 2010 23:12:26 -0400 (EDT) Message-ID: <4C4CFCE9.8070303@redhat.com> Date: Sun, 25 Jul 2010 23:11:37 -0400 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH 7/8] writeback: sync old inodes first in background writeback References: <20100723094515.GD5043@localhost> <20100723105719.GE5300@csn.ul.ie> <20100725192955.40D5.A69D9226@jp.fujitsu.com> <20100726030813.GA7668@localhost> In-Reply-To: <20100726030813.GA7668@localhost> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Wu Fengguang Cc: KOSAKI Motohiro , Mel Gorman , Christoph Hellwig , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , Dave Chinner , Chris Mason , Nick Piggin , Johannes Weiner , KAMEZAWA Hiroyuki , Andrew Morton , Andrea Arcangeli , Minchan Kim List-ID: On 07/25/2010 11:08 PM, Wu Fengguang wrote: > We do need some throttling under memory pressure. However stall time > more than 1s is not acceptable. A simple congestion_wait() may be > better, since it waits on _any_ IO completion (which will likely > release a set of PG_reclaim pages) rather than one specific IO > completion. This makes much smoother stall time. > wait_on_page_writeback() shall really be the last resort. > DEF_PRIORITY/3 means 1/16=6.25%, which is closer. I agree with the max 1 second stall time, but 6.25% of memory could be an awful lot of pages to scan on a system with 1TB of memory :) Not sure what the best approach is, just pointing out that DEF_PRIORITY/3 may be too much for large systems... -- All rights reversed -- 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