Date: Sun, 07 Nov 1999 09:26:02 -0500 From: "Daniel M. Eischen" <eischen@vigrid.com> To: Julian Elischer <julian@whistle.com> Cc: "Russell L. Carter" <rcarter@chomsky.Pinyon.ORG>, Poul-Henning Kamp <phk@critter.freebsd.dk>, freebsd-arch@freebsd.org Subject: Re: Threads models and FreeBSD. (Next Step) Message-ID: <38258BFA.B7EA3ECB@vigrid.com> References: <Pine.BSF.4.10.9911070237440.10573-100000@current1.whistle.com>
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Julian Elischer wrote: > > On Tue, 2 Nov 1999, Russell L. Carter wrote: [...] > > Put another way, cramming a process's threads into a single > > scheduling quanta significantly diminishes the suitability of FreeBSD > > as a platform for building high performance and/or RT CORBA apps. > > Let's rephrase this.. > > Firstly 'A single scheduling quanta' is probably a misleading statement. > > firstly it would be > 'A group of quanta' as the process may be at a priority where it gets a > lot of time and there may be only one other process with only 1 quanta > allocated to it.. > 99/100 is pretty close to all you can get.. > > secondly, I see a need to be able to effectively 'fork off a separate > family of threads' that are treated as a separate scheduling entity. > Thsi only makes sense at all if the threads in that group are explicitly > bound to that group, and other threads cannot arbitrarily wander in and > out of the group. Except for very narrow windows where threads holding critical resources (internal to the threads library) are continued until they release the resource. I can also see the need for threads to cross scheduling group boundaries in order to support priority protection and priority ceiling mutexes. > > The sum of the processing quanta for the original and the new class would > be the same as a user process forking to run 2 processes in parallel, and > would be limited by the same mechanisms. The second process could not > increaes its priority higher than the parent, just like nice(2) at the > moment. (You wuld need root priority to do that) Yes! As long as we can "obtain a new quantum" with the ability (as root) to raise priority or enter a different scheduling class, then I am satisified :-) Dan Eischen eischen@vigrid.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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