Date: Mon, 2 Jul 2001 13:19:04 -0700 (PDT) From: Julian Elischer <julian@elischer.org> To: "Michael C . Wu" <keichii@peorth.iteration.net> Cc: "E.B. Dreger" <eddy+public+spam@noc.everquick.net>, Alfred Perlstein <bright@sneakerz.org>, smp@FreeBSD.ORG Subject: Re: per cpu runqueues, cpu affinity and cpu binding. Message-ID: <Pine.BSF.4.21.0107021303460.13213-100000@InterJet.elischer.org> In-Reply-To: <20010702115044.C99436@peorth.iteration.net>
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On Mon, 2 Jul 2001, Michael C . Wu wrote: > On Mon, Jul 02, 2001 at 04:42:51PM +0000, E.B. Dreger scribbled: > | > | Not just keeping a given process on the same CPU... but what about a > | "process type"? i.e., if different processes have the same ELF header, > | run them _all_ on the CPU _unless_ it leaves another CPU excessively idle. > | > | Why waste [code] cache on multiple processors when you can keep things on > | one? > > Because it is very difficult to worry about these things. And the performance > gain might probably be less than the overhead of comparing the headers. One could note a prefered processor in the vnode of the executable exec() could take note of this and switch processors if the load balancing algorythm showed that the new processor would not become overly stresssed at the idea. (do all /bin/sh run on the sme processor?) or maybe the vnode can note which processors it is already on (more than one). > > | > I don't think doing per-thread affinity is a good idea. Because > | > we want to keep threads lightweight. > | > | !!! > > Please elaborate. I don't understand what three exclamation marks > are supposed to mean. At USENIX we decided to proceed with the KSE work. I have already re-implemented the proc-splitting patches from January and have split the proc structure into parts to support threads. In this case teh processor affinity stuff that alfred has done are already in a per-thread (per kse) basis. Individual threads may migrate between KSEs but if teh program acts to implement KSEs (thread carriers) on multiple processors then they will try STAY on particular processors. As a side issue I plan on NOT ALLOWING multiple KSEs (thread carriers?) from the same thread group in the same process to be on the same processor. SO load balancing and processor affinity will not apply to the thread-carrying entities (KSEs). Of course the userland thread scheduler has the ultimate say as to which processor a thread is scheduled on. > julian To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-smp" in the body of the message
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