From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [Qemu-devel] [PATCH 4/4] Reallocate dma buffers in read/write path if needed Date: Fri, 03 Oct 2008 18:35:18 -0500 Message-ID: <48E6AC36.3060404@codemonkey.ws> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: qemu-devel@nongnu.org, Ryan Harper , Anthony Liguori , kvm@vger.kernel.org To: Paul Brook Return-path: Received: from an-out-0708.google.com ([209.85.132.244]:55976 "EHLO an-out-0708.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753168AbYJCXfX (ORCPT ); Fri, 3 Oct 2008 19:35:23 -0400 Received: by an-out-0708.google.com with SMTP id d40so105523and.103 for ; Fri, 03 Oct 2008 16:35:22 -0700 (PDT) In-Reply-To: <200810040017.09081.paul@codesourcery.com> Sender: kvm-owner@vger.kernel.org List-ID: 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 >