Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262907AbVD2TnU (ORCPT ); Fri, 29 Apr 2005 15:43:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262909AbVD2TnU (ORCPT ); Fri, 29 Apr 2005 15:43:20 -0400 Received: from wproxy.gmail.com ([64.233.184.204]:24018 "EHLO wproxy.gmail.com") by vger.kernel.org with ESMTP id S262907AbVD2TnN convert rfc822-to-8bit (ORCPT ); Fri, 29 Apr 2005 15:43:13 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:reply-to:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=XqUyFCHdk3Oucg/OAL5po0wNmVmMEX1iYvO+TbYMBEbfSnfr2bcggYmujBcNNA8AFxYwA5xcAG0poqK23WxkT4yd+A4VtDUgGuwZyvGwr5apz0pxo4BA7CRavQcc4cNU4NQdRnZX1374VGNWmioDyJXQJKrgf0JizDfthsAKTWQ= Message-ID: <5ebee0d1050429124333776354@mail.gmail.com> Date: Fri, 29 Apr 2005 15:43:10 -0400 From: Bill Jordan Reply-To: bjordan@infinicon.com To: Roland Dreier Subject: Re: RDMA memory registration (was: [openib-general] Re: [PATCH][RFC][0/4] InfiniBand userspace verbs implementation) Cc: Caitlin Bestler , Andrew Morton , hch@infradead.org, linux-kernel@vger.kernel.org, openib-general@openib.org, Timur Tabi In-Reply-To: <52d5sdjzup.fsf_-_@topspin.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT Content-Disposition: inline References: <20050425135401.65376ce0.akpm@osdl.org> <20050426084234.A10366@topspin.com> <52mzrlsflu.fsf@topspin.com> <20050426122850.44d06fa6.akpm@osdl.org> <5264y9s3bs.fsf@topspin.com> <426EA220.6010007@ammasso.com> <20050426133752.37d74805.akpm@osdl.org> <5ebee0d105042907265ff58a73@mail.gmail.com> <469958e005042908566f177b50@mail.gmail.com> <52d5sdjzup.fsf_-_@topspin.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1118 Lines: 25 On 4/29/05, Roland Dreier wrote: > b) (maybe someday?) Add a VM_ALWAYSCOPY flag and extend mprotect() > with PROT_ALWAYSCOPY so processes can mark pages to be > pre-copied into child processes, to handle the case where only > half a page is registered. Are you suggesting making the partial pages their own VMA, or marking the entire buffer with this flag? I originally thought the entire buffer should be copy on fork (instead of copy on write), and I believe this is the path Mellanox was pursing with the VM_NO_COW flag. However, if applications are registering gigs of ram, it would be very bad to have the entire area copied on fork. On the other hand, I've always wondered about the choice to leave holes in the child process's address space. I would have chosen to map the zero page instead. -- Bill Jordan InfiniCon Systems - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/