From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1MiFqX-0002Bo-0O for qemu-devel@nongnu.org; Mon, 31 Aug 2009 18:59:33 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1MiFqS-00029B-3Y for qemu-devel@nongnu.org; Mon, 31 Aug 2009 18:59:32 -0400 Received: from [199.232.76.173] (port=54897 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1MiFqR-000296-PU for qemu-devel@nongnu.org; Mon, 31 Aug 2009 18:59:27 -0400 Received: from mail2.shareable.org ([80.68.89.115]:59960) by monty-python.gnu.org with esmtps (TLS-1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1MiFqR-0002XV-7y for qemu-devel@nongnu.org; Mon, 31 Aug 2009 18:59:27 -0400 Date: Mon, 31 Aug 2009 23:59:25 +0100 From: Jamie Lokier Subject: Re: [Qemu-devel] [PATCH 1/4] block: add enable_write_cache flag Message-ID: <20090831225925.GG24318@shareable.org> References: <20090831201627.GA4811@lst.de> <20090831201651.GA4874@lst.de> <20090831220950.GB24318@shareable.org> <20090831221622.GA8834@lst.de> <4A9C5463.4090904@codemonkey.ws> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4A9C5463.4090904@codemonkey.ws> List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: Christoph Hellwig , qemu-devel@nongnu.org Anthony Liguori wrote: > Can someone do some benchmarking with cache=writeback and fdatasync > first and quantify what the real performance impact is? Unfortunately we can't yet quantify the impact on the hardware I care about (ordinary consumer PCs with non-NCQ SATA disks), because Linux hosts don't *yet* implement O_SYNC or fdatasync properly. I would expect the performance difference to be much more significant after those are implemented on the host. -- Jamie