From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f46.google.com (mail-pa0-f46.google.com [209.85.220.46]) by kanga.kvack.org (Postfix) with ESMTP id 68F996B0035 for ; Mon, 3 Feb 2014 20:53:36 -0500 (EST) Received: by mail-pa0-f46.google.com with SMTP id rd3so7757794pab.5 for ; Mon, 03 Feb 2014 17:53:36 -0800 (PST) Received: from lgemrelse7q.lge.com (LGEMRELSE7Q.lge.com. [156.147.1.151]) by mx.google.com with ESMTP id yy4si22562608pbc.99.2014.02.03.17.53.33 for ; Mon, 03 Feb 2014 17:53:35 -0800 (PST) Date: Tue, 4 Feb 2014 10:53:32 +0900 From: Joonsoo Kim Subject: Re: [patch] mm, compaction: avoid isolating pinned pages fix Message-ID: <20140204015332.GA14779@lge.com> References: <20140203095329.GH6732@suse.de> <20140204000237.GA17331@lge.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: David Rientjes Cc: Mel Gorman , Andrew Morton , Rik van Riel , linux-kernel@vger.kernel.org, linux-mm@kvack.org On Mon, Feb 03, 2014 at 05:20:46PM -0800, David Rientjes wrote: > On Tue, 4 Feb 2014, Joonsoo Kim wrote: > > > I think that you need more code to skip this type of page correctly. > > Without page_mapped() check, this code makes migratable pages be skipped, > > since if page_mapped() case, page_count() may be more than zero. > > > > So I think that you need following change. > > > > (!page_mapping(page) && !page_mapped(page) && page_count(page)) > > > > These pages returned by get_user_pages() will have a mapcount of 1 so this > wouldn't actually fix the massive lock contention. page_mapping() is only > going to be NULL for pages off the lru like these are for > PAGE_MAPPING_ANON. Okay. It can't fix your situation. Anyway, *normal* anon pages may be mapped and have positive page_count(), so your code such as '!page_mapping(page) && page_count(page)' makes compaction skip these *normal* anon pages and this is incorrect behaviour. Thanks. -- 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