On Tue, 29 Mar 2005 21:11:07 +1000, Peter Jeremy <[EMAIL PROTECTED]> wrote: > On Mon, 2005-Mar-28 23:23:19 -0800, David Leimbach wrote: > >meant to send this to the list too... sorry > >> Are you implying DragonFly uses FPU/SIMD? For that matter does any kernel? > > > >I believe it does use SIMD for some of it's fast memcopy stuff for > >it's messaging system > >actually. I remember Matt saying he was working on it. > > > >http://leaf.dragonflybsd.org/mailarchive/kernel/2004-04/msg00262.html > > That's almost a year ago and specifically for the amd64. Does anyone > know what the results were?
Actually I don't remember precisely what came of it, but I do remember that we had some interesting stability issues while Matt worked out some bugs around that time, I think they were related to the SIMD stuff. > > >If you can manage the alignment issues it can be a huge win. > > For message passing within the kernel, you should be able to mandate > alignment as part of the API. > > I see the bigger issue being the need to save/restore the SIMD > engine's state during a system call. Currently, this is only saved on > if a different process wants to use the SIMD engine. For MMX, the > SIMD state is the FPU state - which is non-trivial. The little > reading I've done suggests that SSE and SSE2 are even larger. > > Saving the SIMD state would be more expensive that using integer > registers for small (and probably medium-sized) copies. > Yes, you'd have to have a fairly smart copy to know when to avoid the setup overhead. Apple's bcopy stuff does a lot of checking if I recall. It's been a while since I've looked at that either. [the stuff that's mapped into the COMM_PAGE of Mac OS X 10.3.x processes] Dave > -- > Peter Jeremy > _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "[EMAIL PROTECTED]"
