From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx181.postini.com [74.125.245.181]) by kanga.kvack.org (Postfix) with SMTP id 40F546B0032 for ; Thu, 8 Aug 2013 03:26:38 -0400 (EDT) Received: from eucpsbgm1.samsung.com (unknown [203.254.199.244]) by mailout4.w1.samsung.com (Oracle Communications Messaging Server 7u4-24.01(7.0.4.24.0) 64bit (built Nov 17 2011)) with ESMTP id <0MR700LK5BBWDH50@mailout4.w1.samsung.com> for linux-mm@kvack.org; Thu, 08 Aug 2013 08:26:36 +0100 (BST) Message-id: <1375946794.25843.1.camel@AMDC1943> Subject: Re: [RFC PATCH 3/4] mm: add zbud flag to page flags From: Krzysztof Kozlowski Date: Thu, 08 Aug 2013 09:26:34 +0200 In-reply-to: <52012B35.90801@intel.com> References: <1375771361-8388-1-git-send-email-k.kozlowski@samsung.com> <1375771361-8388-4-git-send-email-k.kozlowski@samsung.com> <52012B35.90801@intel.com> Content-type: text/plain; charset=UTF-8 Content-transfer-encoding: 7bit MIME-version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: Seth Jennings , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Mel Gorman , Bartlomiej Zolnierkiewicz , Marek Szyprowski , Kyungmin Park Hi, On wto, 2013-08-06 at 09:58 -0700, Dave Hansen wrote: > On 08/05/2013 11:42 PM, Krzysztof Kozlowski wrote: > > +#ifdef CONFIG_ZBUD > > + /* Allocated by zbud. Flag is necessary to find zbud pages to unuse > > + * during migration/compaction. > > + */ > > + PG_zbud, > > +#endif > > Do you _really_ need an absolutely new, unshared page flag? > The zbud code doesn't really look like it uses any of the space in > 'struct page'. > > I think you could pretty easily alias PG_zbud=PG_slab, then use the > page->{private,slab_cache} (or some other unused field) in 'struct page' > to store a cookie to differentiate slab and zbud pages. How about using page->_mapcount with negative value (-129)? Just like PageBuddy()? Best regards, Krzysztof -- 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