From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758867AbZHRMYz (ORCPT ); Tue, 18 Aug 2009 08:24:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758544AbZHRMYy (ORCPT ); Tue, 18 Aug 2009 08:24:54 -0400 Received: from sinclair.provo.novell.com ([137.65.248.137]:22532 "EHLO sinclair.provo.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752131AbZHRMYy convert rfc822-to-8bit (ORCPT ); Tue, 18 Aug 2009 08:24:54 -0400 Message-Id: <4A8A65540200005A000528EA@sinclair.provo.novell.com> X-Mailer: Novell GroupWise Internet Agent 8.0.1 Beta Date: Tue, 18 Aug 2009 06:24:52 -0600 From: "Gregory Haskins" To: Cc: , , , , , , Subject: Re: [PATCH v3 3/6] vbus: add a "vbus-proxy" bus model for References: <4A8A654A0200005A000528E7@sinclair.provo.novell.com> <4A8A65540200005A000528EA@sinclair.provo.novell.com> In-Reply-To: <4A8A65540200005A000528EA@sinclair.provo.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (Again on the top post) No, Avi, nothing has changed to my knowledge. I just saw that you and Michael were heading down the same path, so I thought I might interject that we've already covered that ground. As of right now, I am of the opinion that its not worth any change in the short term, and may be worth IOoHC in the long term (primarily so that mmios get a boost) -greg. -----Original Message----- From: Avi Kivity To: Gregory Haskins Cc: Cc: Cc: Cc: Cc: Cc: Cc: Sent: 8/18/2009 6:19:53 AM Subject: Re: [PATCH v3 3/6] vbus: add a "vbus-proxy" bus model for vbus_drive On 08/18/2009 03:11 PM, Gregory Haskins wrote: > Sorry for the toppost. Still not at the office. > > I just wanted to add that we've already been through this disussion once. (Search "haskins hypercall lkml" on google and I'm sure you are bound to see hits. > > Your numbers showed a 350ns difference on fairly old (by now) hardware. I doubt the difference will exceed 200ns now. > The fact is: the original vbus was designed with hypercalls, and it drew much of these same critisims. In the end, hypercalls are only marginally faster than PIO (iirc, 450ns faster, and shrinking), so we decided that it was not worth further discussion at the time. > Has anything changed? > A better solution is probably PIOoHC, so that you retain the best properties of both. The only problem with the entire PIOx approach is that its x86 specific, but that is an entirely different thread. > pio is nicely abstracted by PCI. virtio-pci will use pio on x86 and mmio on non-x86. -- error compiling committee.c: too many arguments to function