From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 8 May 2002 04:13:49 -0700 From: William Lee Irwin III Subject: Re: [PATCH] rmap 13a Message-ID: <20020508111349.GI15756@holomorphy.com> References: <20020507183741.A25245@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Description: brief message Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org Return-Path: To: Samuel Ortiz Cc: Christoph Hellwig , Rik van Riel , linux-mm@kvack.org List-ID: On Wed, May 08, 2002 at 04:06:58AM -0700, Samuel Ortiz wrote: > Some discontiguous architectures (ARM, for example) may be interested in > getting rid of page->virtual, and thus shrinking the struct page size. > So you may want to get the possibility of having > (!CONFIG_HIGHMEM)&&CONFIG_DISCONTIGMEM and not wanting page->virtual. > So, WANT_PAGE_VIRTUAL can not be defined with CONFIG_HIGHMEM || > CONFIG_DISCONTIGMEM. > However, I should modify my patch in order for the changes to take place > only if (!CONFIG_HIGHMEM)&&(CONFIG_DISCONTIG_MEM)&&(!WANT_PAGE_VIRTUAL). > I can come back with the right changes if that makes sense to you. Also, to be perfectly clear despite my message of perhaps extreme conservatism regarding space conservation, I believe the time/space tradeoff is an architectural consideration. Though I specifically requested that a calculated UNMAP_NR_DENSE() be implemented, I by no means oppose the usage of page->virtual for those architectures where demonstrable performance benefits arise from the additional space consumption of the extra field. Cheers, Bill -- 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/