From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 05 Jan 2006 18:47:22 +0900 From: IWAMOTO Toshihiro Subject: Re: [PATCH 6/9] clockpro-clockpro.patch In-Reply-To: <1136028546.17853.69.camel@twins> References: <20051230223952.765.21096.sendpatchset@twins.localnet> <20051230224312.765.58575.sendpatchset@twins.localnet> <20051231002417.GA4913@dmt.cnet> <1136028546.17853.69.camel@twins> MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Message-Id: <20060105094722.897C574030@sv1.valinux.co.jp> Sender: owner-linux-mm@kvack.org Return-Path: To: Peter Zijlstra Cc: Marcelo Tosatti , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Christoph Lameter , Wu Fengguang , Nick Piggin , Marijn Meijles , Rik van Riel List-ID: At Sat, 31 Dec 2005 12:29:06 +0100, Peter Zijlstra wrote: > > Forgot one in the previous mail. > > On Fri, 2005-12-30 at 22:24 -0200, Marcelo Tosatti wrote: > > Please make it easier for others to understand why the hands > > swap, and when, and why. > > Its not the hands that swap, its the lists. The hands will lap each > other, like the minute hand will lap the hour hand every ~65 minutes. > > Let me try some ascii art. > > ==== > ^---<>---v > ==== > > '=' a page > '^---<' hand cold > '>---v' hand hot > > now let hand cold move 4 pages: > > > ^---<>---v > ======== > > ie. hand hot and hand cold have the same position. > now if we want to move hand cold one more position this happens: > > ======= > ^---<>---v > = > > see the swap? Is it okay to allow Hcold to lap Hhot? In my understanding of CLOCK-Pro, such lapping causes sudden increase in the distance between Hhot and Hcold. As that distance is an important parameter of page aging/replacement decisions, I'm afraid that such lapping would result in incorrect page aging and bad performance. I guess the alternative is to advance Hhot together with Hcold, but I'm not sure this is correct, either. Please enlighten me. -- IWAMOTO Toshihiro -- 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