Date: Tue, 21 Nov 2000 16:23:00 -0500 (EST) From: Daniel Eischen <eischen@vigrid.com> To: Terry Lambert <tlambert@primenet.com> Cc: Julian Elischer <julian@elischer.org>, arch@FreeBSD.ORG, smp@FreeBSD.ORG Subject: Re: Threads (KSE etc) comments Message-ID: <Pine.SUN.3.91.1001121160717.7102A-100000@pcnet1.pcnet.com> In-Reply-To: <200011211824.LAA27595@usr08.primenet.com>
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On Tue, 21 Nov 2000, Terry Lambert wrote: > > yes, but that gives the ability to use M times as much CPU as a > > nonthreaded process. > > If you won't give it to me, I'll just take it, instead, either > by using rfork() and a shared memory segment for my global data, > which gets me the equivalenet of a threaded environment, for all > practical purposes, or I'll just fork() and run multiple instances > of myself. Either way, you don't get to tell me not to compete > as multiple processes, and I can throw a KSEG based policy out the > window, without needing your permission to do it. Worse, there > is additional context switch overhead introduced by this (the > same reason Linux kernel threads are a bad idea), and everyone > gets to pay the penalty for my application. I have to agree with Terry. You can't dictate what application writers will do. If they want more CPU and they can't get it with the threading model we provide, then they will get it another way. Limiting PTHREAD_SCOPE_PROCESS threads to 1 KSEG with only 1 quantum doesn't stop someone from [r]fork()'ing to get more CPU. Let's admit that this is what some applications will want to do and allow them to do it within our threading model. No, we won't do it by default, but we can provide simple hooks to allow an application to request more "CPU reservations" (a KSEG under the current definition). Note that I am only talking about scope process threads. Scope system threads are bound to their own KSEG/KSE pair. -- Dan Eischen To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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