From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <489313AC.3080605@linux-foundation.org> Date: Fri, 01 Aug 2008 08:46:20 -0500 From: Christoph Lameter MIME-Version: 1.0 Subject: Re: [PATCH] Update Unevictable LRU and Mlocked Pages documentation References: <1217452439.7676.26.camel@lts-notebook> <4891C8BC.1020509@linux-foundation.org> <1217515429.6507.7.camel@lts-notebook> In-Reply-To: <1217515429.6507.7.camel@lts-notebook> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Lee Schermerhorn Cc: Andrew Morton , linux-mm , KOSAKI Motohiro , Kamezawa Hiroyuki , Rik van Riel , Nick Piggin List-ID: Lee Schermerhorn wrote: > On Thu, 2008-07-31 at 09:14 -0500, Christoph Lameter wrote: >>> +Why maintain unevictable pages on an additional LRU list? Primarily because >>> +we want to be able to migrate unevictable pages between nodes--for memory >>> +deframentation, workload management and memory hotplug. The linux kernel can >>> +only migrate pages that it can successfully isolate from the lru lists. >>> +Therefore, we want to keep the unevictable pages on an lru-like list, where >>> +they can be found by isolate_lru_page(). >> The primary motivation for me was to get rid of the useless scanning >> of pages under memory pressure which led to live lock scenarios. >> mlocked pages are migratable now so the changes do not really change >> anything there. The unevictable lists are also necessary to spill >> pages back to the regular LRUs when unevictable pages become evictable >> again. > > Hi, Christoph: > > Yes, mlocked pages are migratable now [before the unevictable > lru/mlocked pages patches], but that's because they reside on the LRU > lists. If we just moved them off to a list that isn't known to > isolate_lru_page(), it wouldn't find them and they wouldn't be migrated. > So, I want to keep them on an LRU-like list so that they remain > migratable. I was just explaining that rationale in the doc. Yes I know and I think the rationale is not convincing if the justification of the additional LRU is primarily for page migration. -- 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