Date: Sun, 12 Dec 1999 23:25:48 -0500 (EST) From: Chuck Robey <chuckr@picnic.mat.net> To: "Russell L. Carter" <rcarter@pinyon.org> Cc: Nate Williams <nate@mt.sri.com>, Arun Sharma <adsharma@sharmas.dhs.org>, freebsd-arch@freebsd.org Subject: Re: Thread scheduling Message-ID: <Pine.BSF.4.10.9912122325060.16082-100000@picnic.mat.net> In-Reply-To: <19991211192742.4C7504A@pinyon.org>
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On Sat, 11 Dec 1999, Russell L. Carter wrote: > > %> Not a guarantee, but would it be a good thing to have them > %> "co-scheduled" (or a bias towards that likelihood). > % > %But, I can't see any advantage to have them co-scheduled. > > In the realm of parallel numerical algorithms there are > quite a lot of practical algorithms that require cross > "task" communication and to the extent that the "tasks" > are not executed in roughly synchronous fashion so that > their intricate communication schedules may be carried > out more or less non-blocking then the algorithm > suffers from disastrous multicpu inefficiency. > Typically, these "tasks" share miniscule amounts of data, > but any "waiting" is fatal to scalable throughput. > Hence the development of the "gang scheduling" notion > that Arun referred to. This is most highly refined > and effectively implemented in Cray UNICOS systems. > > But I wouldn't worry about it. It's a small slice of > the whole customer pie, and causes indigestion for > my particular fetish, which is independently > schedulable (ala POSIX) threads capable of > meeting QOS guarantees. :-) OK, thanks, guys. That question's done. I have more, but I need to investigate code now, so as not to waste more time. ---------------------------------------------------------------------------- Chuck Robey | Interests include C programming, Electronics, 213 Lakeside Dr. Apt. T-1 | communications, and signal processing. Greenbelt, MD 20770 | I run picnic.mat.net: FreeBSD-current(i386) and (301) 220-2114 | jaunt.mat.net : FreeBSD-current(Alpha) ---------------------------------------------------------------------------- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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