Date: Thu, 10 Jan 2002 14:49:13 -0800 (PST) From: Julian Elischer <julian@elischer.org> To: Nate Williams <nate@yogotech.com> Cc: Terry Lambert <tlambert2@mindspring.com>, Kelly Yancey <kbyanc@posi.net>, Alfred Perlstein <bright@mu.org>, Daniel Eischen <eischen@pcnet1.pcnet.com>, Dan Eischen <eischen@vigrid.com>, Peter Wemm <peter@wemm.org>, Archie Cobbs <archie@dellroad.org>, arch@FreeBSD.ORG Subject: Re: Request for review: getcontext, setcontext, etc Message-ID: <Pine.BSF.4.21.0201101448230.59070-100000@InterJet.elischer.org> In-Reply-To: <15422.6499.274704.270810@caddis.yogotech.com>
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Remember that in some hardware (e.g. x86)
FP registers are used for bulk data transfer.
same thing applies when they are used in this way..
On Thu, 10 Jan 2002, Nate Williams wrote:
> > > If the context switch overhead is the same (or worse) with a userland
> > > scheduler, then what are the "effeciency reasons" for having it? Where does
> > > the userland scheduler reclaim it's lost ground? The only things my limited
> > > understanding can produce are a number of trivial data structures that can be
> > > moved from the kernel to userland. :/
> > > It seems to me that if {get,set}context involve kernel calls, then any
> > > userland scheduler would, by definition, require N+1 context switches where N
> > > is the number of context switches required by a kernel-only scheduler. The
> > > extra 1 coming from invoking the scheduler context itself.
> >
> > Remember that this is only true if someone is stupid enough to
> > use the FPU, which is only useful for very specific tasks, most
> > of which are non-threaded.
>
> Huh? Methinks Terry needs to make assume the world is just a *teeny*
> bit larger than his narrow-view.
>
> > For graphics and line drawing -- even
> > curve drawing -- the fast graphics world all uses integer math
> > and tables. That leave us with special purpose number crunching
> > that doesn't care incredibly deeply about its significant digits
> > running away to exponent&mantissa-land.
>
> Even simple statistics use FP math. You're implying that FPU should
> only be used by folks who have a real *NEED* for it, which is humerous
> considering you're the one who usually bangs on the drum to make FreeBSD
> useful for more folks. :)
>
>
>
> Nate
>
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