From owner-freebsd-arch@FreeBSD.ORG  Thu Oct 27 21:05:51 2011
Return-Path: <owner-freebsd-arch@FreeBSD.ORG>
Delivered-To: freebsd-arch@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id B2857106566C
	for <freebsd-arch@freebsd.org>; Thu, 27 Oct 2011 21:05:51 +0000 (UTC)
	(envelope-from adrian.chadd@gmail.com)
Received: from mail-vw0-f54.google.com (mail-vw0-f54.google.com
	[209.85.212.54])
	by mx1.freebsd.org (Postfix) with ESMTP id 711288FC17
	for <freebsd-arch@freebsd.org>; Thu, 27 Oct 2011 21:05:51 +0000 (UTC)
Received: by vws11 with SMTP id 11so4452735vws.13
	for <freebsd-arch@freebsd.org>; Thu, 27 Oct 2011 14:05:50 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma;
	h=mime-version:sender:in-reply-to:references:date
	:x-google-sender-auth:message-id:subject:from:to:cc:content-type;
	bh=kPc6jfp04qkJ3pGiCyFuL3FEXvmIyrqSfTBoX/Jod6s=;
	b=R34C9+Uwn32e//MH+5hePjgWLVY3+e2VRsTPOgO3Ium1nchpQhyQ/co8qEReQC8AHC
	tMwB7BRMyQAot2LjwOwa9H2AHNY/KQfJ4Sw0ji3MgM0w/ZRYn680UP8QkZuULHIb7rmE
	pxyTeFTx7lrp9PUrzQJcd4RXdjYmys1yM77vY=
MIME-Version: 1.0
Received: by 10.52.72.227 with SMTP id g3mr785800vdv.10.1319749550723; Thu, 27
	Oct 2011 14:05:50 -0700 (PDT)
Sender: adrian.chadd@gmail.com
Received: by 10.52.176.1 with HTTP; Thu, 27 Oct 2011 14:05:50 -0700 (PDT)
In-Reply-To: <4EA9C197.9080407@feral.com>
References: <CAJ-VmonFJG3xLn2JvarOUN6o-e7MC+A+=W9_vocZqY6L3CmTmQ@mail.gmail.com>
	<4EA9C197.9080407@feral.com>
Date: Fri, 28 Oct 2011 05:05:50 +0800
X-Google-Sender-Auth: R1v_z06l37E6P8dM2BYRNSI0nvY
Message-ID: <CAJ-Vmomuze+fX_NRhB11dJbZX54c=Gqj6EpxjjnP17BtZxCaNQ@mail.gmail.com>
From: Adrian Chadd <adrian@freebsd.org>
To: mj@feral.com
Content-Type: text/plain; charset=ISO-8859-1
Cc: freebsd-arch@freebsd.org
Subject: Re: newbus IO ordering semantics - moving forward
X-BeenThere: freebsd-arch@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Discussion related to FreeBSD architecture <freebsd-arch.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-arch>,
	<mailto:freebsd-arch-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-arch>
List-Post: <mailto:freebsd-arch@freebsd.org>
List-Help: <mailto:freebsd-arch-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-arch>,
	<mailto:freebsd-arch-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 27 Oct 2011 21:05:51 -0000

On 28 October 2011 04:39, Matthew Jacob <mj@feral.com> wrote:

> No. Please don't change the current semantics which are well understood if
> only fitfully adhered to. This would put us in the position of having some
> drivers possibly work slower because they didn't do the "lazy" request.
>
> I also am not sure I agree with your characterization of linux semantics.

Hi,

The point is, all (most?) of the bus glue does flushes if needed. Ie,
if I understand what's going on:

* amd64/intel, it's not needed;
* mips doesn't implement it yet;
* ppc (and sparc?) implement a bus flush on each operation anyway.


Adrian