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Date:      Fri, 28 Oct 2011 05:05:50 +0800
From:      Adrian Chadd <adrian@freebsd.org>
To:        mj@feral.com
Cc:        freebsd-arch@freebsd.org
Subject:   Re: newbus IO ordering semantics - moving forward
Message-ID:  <CAJ-Vmomuze%2BfX_NRhB11dJbZX54c=Gqj6EpxjjnP17BtZxCaNQ@mail.gmail.com>
In-Reply-To: <4EA9C197.9080407@feral.com>
References:  <CAJ-VmonFJG3xLn2JvarOUN6o-e7MC%2BA%2B=W9_vocZqY6L3CmTmQ@mail.gmail.com> <4EA9C197.9080407@feral.com>

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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



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