From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1IpWMF-0005Ei-8H for qemu-devel@nongnu.org; Tue, 06 Nov 2007 16:53:15 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1IpWMC-0005A6-1B for qemu-devel@nongnu.org; Tue, 06 Nov 2007 16:53:14 -0500 Received: from [199.232.76.173] (helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1IpWMB-00059p-Nr for qemu-devel@nongnu.org; Tue, 06 Nov 2007 16:53:11 -0500 Received: from grayson.netsweng.com ([207.235.77.11]) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1IpWMB-0005Sz-8s for qemu-devel@nongnu.org; Tue, 06 Nov 2007 16:53:11 -0500 Received: from amavis by grayson.netsweng.com with scanned-ok (Exim 3.36 #1 (Debian)) id 1IpWLl-0004SP-00 for ; Tue, 06 Nov 2007 16:52:45 -0500 Received: from grayson.netsweng.com ([127.0.0.1]) by localhost (grayson.netsweng.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id wR3yvWXtn5e6 for ; Tue, 6 Nov 2007 16:52:28 -0500 (EST) Received: from [71.31.91.43] (helo=trantor.stuart.netsweng.com) by grayson.netsweng.com with esmtp (Exim 3.36 #1 (Debian)) id 1IpWLT-0004SE-00 for ; Tue, 06 Nov 2007 16:52:27 -0500 Date: Tue, 6 Nov 2007 16:52:05 -0500 (EST) From: Stuart Anderson Subject: Re: [Qemu-devel] RFC: x86_64 Best way to fix 'cast to pointer from integer of different size' problems? In-Reply-To: <4730C8EC.8030808@bellard.org> Message-ID: References: <1194110810.13889.25.camel@hephaestion> <200711031752.20135.paul@codesourcery.com> <1194292268.5154.73.camel@phantasm.home.enterpriseandprosperity.com> <200711060105.04529.paul@codesourcery.com> <4730C8EC.8030808@bellard.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org On Tue, 6 Nov 2007, Fabrice Bellard wrote: > Paul Brook wrote: >> [...] >> Personally I like the locking interface as it allows a zero-copy >> implementation. However the kernel uses a copying interface, and my >> understanding is that other qemu maintainers also prefer the copying >> interface. > > At least I don't think it is critical performance wise, especially if > the page flag checks are added ! Before you added the current zero copy > interface, my plan was to use a zero copy interface just for big buffers > such as the one for read/write. By the time you consider the different combinations of targets & hosts, most of the opportunities for zero copy are eliminated anyway. Byte ordering and structure packing amd content differences mean that we can't do zero-copy except in the rare circumstance that the host & target match is all of these respects. The read & write buffers would still benefit from zero copy, but nearly everything else has to be touched anyway. Stuart Stuart R. Anderson anderson@netsweng.com Network & Software Engineering http://www.netsweng.com/ 1024D/37A79149: 0791 D3B8 9A4C 2CDC A31F BD03 0A62 E534 37A7 9149