From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 1 Aug 2008 10:06:23 -0400 From: Rik van Riel Subject: Re: [PATCH] Update Unevictable LRU and Mlocked Pages documentation Message-ID: <20080801100623.4aae3e37@bree.surriel.com> In-Reply-To: <489313AC.3080605@linux-foundation.org> References: <1217452439.7676.26.camel@lts-notebook> <4891C8BC.1020509@linux-foundation.org> <1217515429.6507.7.camel@lts-notebook> <489313AC.3080605@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: Lee Schermerhorn , Andrew Morton , linux-mm , KOSAKI Motohiro , Kamezawa Hiroyuki , Nick Piggin List-ID: On Fri, 01 Aug 2008 08:46:20 -0500 Christoph Lameter wrote: > Yes I know and I think the rationale is not convincing if the justification > of the additional LRU is primarily for page migration. Basically there are two alternatives: 1) treat unevictable pages just like we treat other pages in the system, which means we get to use the same code to manipulate them, the same code to isolate them (for migrate, etc), the same code to keep track of the statistics, etc... 2) treat unevictable pages differently (not put them on a list) and have special statistics code, special code to isolate them, special code to detect them, etc... Because pretty much every time we move a page onto or off of the unevictable list, we also touch the list_head in the page for other reasons (typically to add the page to or remove from a normal LRU list), we thought it would make the most sense to go with the approach that needs the least amount of special code for the unevictable pages. Besides, a locked page is locked - it should go through fewer list manipulations than the normal file and anon pages ever will, so if the list manipulation shows up as a bottleneck it will show up as a bottleneck for the evictable pages first... -- 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