Date: Fri, 28 Oct 2011 00:37:10 -0700 From: John-Mark Gurney <jmg@funkthat.com> To: Adrian Chadd <adrian@freebsd.org> Cc: freebsd-arch@freebsd.org Subject: Re: newbus IO ordering semantics - moving forward Message-ID: <20111028073710.GP25601@funkthat.com> In-Reply-To: <CAJ-VmonFJG3xLn2JvarOUN6o-e7MC%2BA%2B=W9_vocZqY6L3CmTmQ@mail.gmail.com> References: <CAJ-VmonFJG3xLn2JvarOUN6o-e7MC%2BA%2B=W9_vocZqY6L3CmTmQ@mail.gmail.com>
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Adrian Chadd wrote this message on Fri, Oct 28, 2011 at 04:28 +0800:
> So what I'm proposing is:
>
> * Make the bus default to use ordered semantics, much like what Linux
> does - ie, all IO read/writes (io or memory) are in-order and flushed
> with a barrier;
> * Add an option which allows the driver to request a region with
> loose-running/lazy semantics, what we're supposed to have now, and
> then leave barriers up to the driver;
> * Print out something nice and loud if a driver decides to use the
> lazy/loose semantics, which may result in unpredictable behaviour on
> non-{i386,amd64}.
>
> I'd appreciate some feedback/comments before I go off and code all of this up.
I think we should complain about the drivers that are NOT using the
lazy/loose semantics as those are the drivers that are slower than
they should be, and/or not written properly. Complaining about properly
written drivers that use the lazy/loose semantics when they get updated
to be correct is wrong...
--
John-Mark Gurney Voice: +1 415 225 5579
"All that I will do, has been done, All that I have, has not."
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