From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1EMgXp-0003Fz-BZ for qemu-devel@nongnu.org; Tue, 04 Oct 2005 02:44:57 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1EMgXl-0003F0-Rc for qemu-devel@nongnu.org; Tue, 04 Oct 2005 02:44:55 -0400 Received: from [199.232.76.173] (helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1EMgXl-0003EC-Dp for qemu-devel@nongnu.org; Tue, 04 Oct 2005 02:44:53 -0400 Received: from [195.184.98.160] (helo=virtualhost.dk) by monty-python.gnu.org with esmtp (TLS-1.0:DHE_RSA_3DES_EDE_CBC_SHA:24) (Exim 4.34) id 1EMgWa-0001YY-PT for qemu-devel@nongnu.org; Tue, 04 Oct 2005 02:43:41 -0400 Received: from [62.242.22.158] (helo=router.home.kernel.dk) by virtualhost.dk with esmtp (Exim 3.36 #1) id 1EMgWa-00054O-00 for qemu-devel@nongnu.org; Tue, 04 Oct 2005 08:43:40 +0200 Received: from nelson.home.kernel.dk ([192.168.0.33] helo=kernel.dk) by router.home.kernel.dk with esmtp (Exim 4.22) id 1EMgWY-0008Pf-Is for qemu-devel@nongnu.org; Tue, 04 Oct 2005 08:43:38 +0200 Date: Tue, 4 Oct 2005 08:44:17 +0200 From: Jens Axboe Subject: Re: [Qemu-devel] [patch] non-blocking disk IO Message-ID: <20051004064415.GF3511@suse.de> References: <4340D479.7030301@stanfordalumni.org> <20051003135837.GC3511@suse.de> <20051004013555.GG4612@kalmia.hozed.org> <20051004052451.GJ4612@kalmia.hozed.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20051004052451.GJ4612@kalmia.hozed.org> 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, Oct 04 2005, Troy Benjegerdes wrote: > What we want is to be able to have the guest OS request some DMA > I/O operation, and have qemu be able to use AIO so that the actual disk > hardware can dump the data directly in the pages the userspace process > on the guest OS ends up wanting it in, avoiding several expensive memcopy > and context switch operations. That should be easy enough to do already, with or without the nonblocking patch. Just make sure to open the files O_DIRECT and align the io buffers and lengths. With a 2.6 host, you can usually get away with 512-b aligment, on 2.4 you may have to ensure 1k/4k alignment. -- Jens Axboe