From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1KluBC-0005aQ-AX for qemu-devel@nongnu.org; Fri, 03 Oct 2008 19:35:26 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1KluBA-0005ZZ-Qk for qemu-devel@nongnu.org; Fri, 03 Oct 2008 19:35:26 -0400 Received: from [199.232.76.173] (port=59075 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1KluBA-0005ZW-M0 for qemu-devel@nongnu.org; Fri, 03 Oct 2008 19:35:24 -0400 Received: from yx-out-1718.google.com ([74.125.44.157]:6711) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1KluBA-0003YL-FU for qemu-devel@nongnu.org; Fri, 03 Oct 2008 19:35:24 -0400 Received: by yx-out-1718.google.com with SMTP id 3so298544yxi.82 for ; Fri, 03 Oct 2008 16:35:22 -0700 (PDT) Message-ID: <48E6AC36.3060404@codemonkey.ws> Date: Fri, 03 Oct 2008 18:35:18 -0500 From: Anthony Liguori MIME-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH 4/4] Reallocate dma buffers in read/write path if needed References: <1223071531-31817-1-git-send-email-ryanh@us.ibm.com> <1223071531-31817-5-git-send-email-ryanh@us.ibm.com> <200810040017.09081.paul@codesourcery.com> In-Reply-To: <200810040017.09081.paul@codesourcery.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paul Brook Cc: Anthony Liguori , Ryan Harper , qemu-devel@nongnu.org, kvm@vger.kernel.org Paul Brook wrote: > On Friday 03 October 2008, Ryan Harper wrote: > >> The default buffer size breaks up larger read/write requests unnecessarily. >> When we encounter requests larger than the default dma buffer, reallocate >> the buffer to support the request. >> > > Allocating unboundedly large host buffers based on guest input seems like a > bad idea. > Perhaps they could be at least bound to phys_ram_size. In general, I don't think there's a correct size to bound them that's less than phys_ram_size. The guest may be issuing really big IO requests. Regards, Anthony Liguori > Paul > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >