From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx204.postini.com [74.125.245.204]) by kanga.kvack.org (Postfix) with SMTP id 3077B6B0062 for ; Mon, 11 Jun 2012 18:49:34 -0400 (EDT) Message-ID: <4FD675FE.1060202@kernel.org> Date: Tue, 12 Jun 2012 07:49:34 +0900 From: Minchan Kim MIME-Version: 1.0 Subject: Re: [PATCH] mm: do not use page_count without a page pin References: <1339373872-31969-1-git-send-email-minchan@kernel.org> <4FD59C31.6000606@jp.fujitsu.com> <20120611074440.GI3094@redhat.com> <20120611133043.GA2340@barrios> <20120611144132.GT3094@redhat.com> In-Reply-To: <20120611144132.GT3094@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrea Arcangeli Cc: Kamezawa Hiroyuki , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Mel Gorman , Michal Hocko On 06/11/2012 11:41 PM, Andrea Arcangeli wrote: > Hi Minchan, > > On Mon, Jun 11, 2012 at 10:30:43PM +0900, Minchan Kim wrote: >> AFAIUC, you mean we have to increase reference count of head page? >> If so, it's not in __count_immobile_pages because it is already race-likely function >> so it shouldn't be critical although race happens. > > I meant, shouldn't we take into account the full size? If it's in the > lru the whole thing can be moved away. > > if (!PageLRU(page)) { > nr_pages = hpage_nr_pages(page); > barrier(); Could you explain why we need barrier? > found += nr_pages; > iter += nr_pages-1; > } > Thanks for the explain. For the normal pages, the logic accounts it as "non-movable pages" so for the consistency, it seems you're right. But let's think about a bit. If THP page isn't LRU and it's still PageTransHuge, I think it's rather rare and although it happens, it means migration/reclaimer is about to split or isolate/putback so it ends up making THP page movable pages. IMHO, it would be better to account it by movable pages. What do you think about it? Thanks. -- 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/ . Don't email: email@kvack.org