From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH v3 1/1] Shared memory uio_pci driver Date: Thu, 25 Mar 2010 12:07:41 +0200 Message-ID: <20100325100741.GB15306@redhat.com> References: <1269497376-21903-1-git-send-email-cam@cs.ualberta.ca> <20100325091552.GB11153@redhat.com> <4BAB2F79.7030706@redhat.com> <20100325094448.GA15306@redhat.com> <4BAB33C6.3060504@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Cam Macdonell , kvm@vger.kernel.org, qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org To: Avi Kivity Return-path: Received: from mx1.redhat.com ([209.132.183.28]:22751 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750927Ab0CYKL0 (ORCPT ); Thu, 25 Mar 2010 06:11:26 -0400 Content-Disposition: inline In-Reply-To: <4BAB33C6.3060504@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Thu, Mar 25, 2010 at 11:58:30AM +0200, Avi Kivity wrote: > On 03/25/2010 11:44 AM, Michael S. Tsirkin wrote: >> On Thu, Mar 25, 2010 at 11:40:09AM +0200, Avi Kivity wrote: >> >>> On 03/25/2010 11:15 AM, Michael S. Tsirkin wrote: >>> >>>> - Why are you using 32 bit long memory accesses for interrupts? >>>> 16 bit IO eould be enough and it's faster. This what virtio-pci does. >>>> >>>> >>>> >>> Why is 16 bit io faster? >>> >> Something to do with need for emulation to get address/data >> for pci memory accesses? >> > > pio is definitely faster than mmio (all that is needed is to set one bit > on the BAR). But 32 vs. 16 makes no difference. Right. That's what I meant. > -- > error compiling committee.c: too many arguments to function