From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id 354296B0023 for ; Fri, 28 Oct 2011 01:01:06 -0400 (EDT) Subject: Re: [patch 4/5]thp: correct order in lru list for split huge page From: Shaohua Li In-Reply-To: <20111027231928.GB29407@barrios-laptop.redhat.com> References: <1319511577.22361.140.camel@sli10-conroe> <20111027231928.GB29407@barrios-laptop.redhat.com> Content-Type: text/plain; charset="UTF-8" Date: Fri, 28 Oct 2011 13:08:58 +0800 Message-ID: <1319778538.22361.152.camel@sli10-conroe> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: Andrew Morton , "aarcange@redhat.com" , Hugh Dickins , Rik van Riel , mel , KAMEZAWA Hiroyuki , linux-mm , lkml On Fri, 2011-10-28 at 07:19 +0800, Minchan Kim wrote: > On Tue, Oct 25, 2011 at 10:59:37AM +0800, Shaohua Li wrote: > > If a huge page is split, all the subpages should live in lru list adjacently > > because they should be taken as a whole. > > In page split, with current code: > > a. if huge page is in lru list, the order is: page, page+HPAGE_PMD_NR-1, > > page + HPAGE_PMD_NR-2, ..., page + 1(in lru page reclaim order) > > b. otherwise, the order is: page, ..other pages.., page + 1, page + 2, ...(in > > lru page reclaim order). page + 1 ... page + HPAGE_PMD_NR - 1 are in the lru > > reclaim tail. > > > > In case a, the order is wrong. In case b, page is isolated (to be reclaimed), > > but other tail pages will not soon. > > > > With below patch: > > in case a, the order is: page, page + 1, ... page + HPAGE_PMD_NR-1(in lru page > > reclaim order). > > in case b, the order is: page + 1, ... page + HPAGE_PMD_NR-1 (in lru page reclaim > > order). The tail pages are in the lru reclaim head. > > > > Signed-off-by: Shaohua Li > > In case of a, it doesn't matter ordering of subpages. > As a huge page, age of sub pages are same. It does matter. Hugepage is split first and then reclaim. if page, page +HPAGE_PMD_NR-1 is reclaimed, you can't get an order-1 page. but if page, page+1 is reclaimed, you can. > In case of b, what a page is located in tail and other subpages are located in head > isn't critical problem. Same way here. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org