Date: Mon, 14 Jul 2003 13:16:17 -0700 From: Peter Wemm <peter@wemm.org> To: Eric Anholt <eta@lclark.edu> Cc: John Baldwin <jhb@FreeBSD.org> Subject: Re: PERFORCE change 33663 for review Message-ID: <20030714201617.C3DF12A7EA@canning.wemm.org> In-Reply-To: <1058006399.1464.52.camel@leguin>
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Eric Anholt wrote: > On Thu, 2003-06-26 at 10:57, John Baldwin wrote: > > On 25-Jun-2003 Peter Wemm wrote: > > > http://perforce.freebsd.org/chv.cgi?CH=33663 > > > > > > Change 33663 by peter@peter_hammer on 2003/06/25 15:05:09 > > > > > > Port sym to amd64 > > > > This is possibly not correct. Do all hammer's support the P3+ > > SFENCE and related instructions? Even i386 should probably be > > using what bus_space_barrier() uses. Heck, sym should probably > > just be using bus_space_barrier anyways. > > It would sure be nice to have an MI call for the bus_space_barrier() > calls that don't need a bus_space_tag. The DRM unfortunately doesn't > (and won't ever, I think) do bus_space, so we have to have > platform-specific ifdefs for read, write, and read/write barriers. Yes, it has the *FENCE instructions, but it still has the same memory ordering semantics. *FENCE has most effect on the SSE/SSE2 instructions, not so much the regular x86* instruction stream, unless MTRR/PAT are in the middle of things as well. This is usually not the case for things like disk IO.. Cheers, -Peter -- Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com "All of this is for nothing if we don't go to the stars" - JMS/B5
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