Date: Thu, 10 Jan 2002 15:44:51 -0700 From: Nate Williams <nate@yogotech.com> To: Terry Lambert <tlambert2@mindspring.com> Cc: Kelly Yancey <kbyanc@posi.net>, Alfred Perlstein <bright@mu.org>, Nate Williams <nate@yogotech.com>, 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: <15422.6499.274704.270810@caddis.yogotech.com> In-Reply-To: <3C3E1870.1E0DA81F@mindspring.com> References: <Pine.BSF.4.21.0201101401420.6961-100000@gateway.posi.net> <3C3E1870.1E0DA81F@mindspring.com>
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> > 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 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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