From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail6.bemta7.messagelabs.com (mail6.bemta7.messagelabs.com [216.82.255.55]) by kanga.kvack.org (Postfix) with ESMTP id BF5076B002D for ; Thu, 27 Oct 2011 19:19:38 -0400 (EDT) Received: by wwf5 with SMTP id 5so4220767wwf.26 for ; Thu, 27 Oct 2011 16:19:35 -0700 (PDT) Date: Fri, 28 Oct 2011 08:19:28 +0900 From: Minchan Kim Subject: Re: [patch 4/5]thp: correct order in lru list for split huge page Message-ID: <20111027231928.GB29407@barrios-laptop.redhat.com> References: <1319511577.22361.140.camel@sli10-conroe> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1319511577.22361.140.camel@sli10-conroe> Sender: owner-linux-mm@kvack.org List-ID: To: Shaohua Li Cc: Andrew Morton , aarcange@redhat.com, Hugh Dickins , Rik van Riel , mel , KAMEZAWA Hiroyuki , linux-mm , lkml 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. In case of b, what a page is located in tail and other subpages are located in head isn't critical problem. Having said that, it's more consistent and simple patch. So I like that. Nice catch, Shaohua! Reviewed-by: Minchan Kim -- Kind regards, Minchan Kim -- 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