From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with ESMTP id 83DF06B004A for ; Tue, 21 Sep 2010 18:25:14 -0400 (EDT) Date: Tue, 21 Sep 2010 15:24:33 -0700 From: Andrew Morton Subject: Re: [PATCH 8/8] writeback: Do not sleep on the congestion queue if there are no congested BDIs or if significant congestion is not being encountered in the current zone Message-Id: <20100921152433.6edd6a87.akpm@linux-foundation.org> In-Reply-To: <20100921221008.GA16323@csn.ul.ie> References: <1284553671-31574-1-git-send-email-mel@csn.ul.ie> <1284553671-31574-9-git-send-email-mel@csn.ul.ie> <20100916152810.cb074e9f.akpm@linux-foundation.org> <20100920095239.GE1998@csn.ul.ie> <20100921144413.abc45d2f.akpm@linux-foundation.org> <20100921221008.GA16323@csn.ul.ie> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Mel Gorman Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Linux Kernel List , Johannes Weiner , Minchan Kim , Wu Fengguang , KAMEZAWA Hiroyuki , KOSAKI Motohiro List-ID: On Tue, 21 Sep 2010 23:10:08 +0100 Mel Gorman wrote: > On Tue, Sep 21, 2010 at 02:44:13PM -0700, Andrew Morton wrote: > > On Mon, 20 Sep 2010 10:52:39 +0100 > > Mel Gorman wrote: > > > > > > > This patch tracks how many pages backed by a congested BDI were found during > > > > > scanning. If all the dirty pages encountered on a list isolated from the > > > > > LRU belong to a congested BDI, the zone is marked congested until the zone > > > > > reaches the high watermark. > > > > > > > > High watermark, or low watermark? > > > > > > > > > > High watermark. The check is made by kswapd. > > > > > > > The terms are rather ambiguous so let's avoid them. Maybe "full" > > > > watermark and "empty"? > > > > > > > > > > Unfortunately they are ambiguous to me. I know what the high watermark > > > is but not what the full or empty watermarks are. > > > > Really. So what's the "high" watermark? > > The high watermark is the point where kswapd goes back to sleep because > enough pages have been reclaimed. It's a proxy measure for memory pressure. > > > From the above text I'm > > thinking that you mean the high watermark is when the queue has a small > > number of requests and the low watermark is when the queue has a large > > number of requests. > > > > I was expecting "zone reaches the high watermark" was the clue that I was > talking about zone watermarks and not an IO queue but it could be better. It was more a rant about general terminology rather than one specific case. > I will try and clarify. How about this as a replacement paragraph? Works for me, thanks. -- 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