Date: Thu, 03 Mar 2005 12:43:53 -0800 From: Julian Elischer <julian@elischer.org> To: David Xu <davidxu@FreeBSD.org> Cc: David Schultz <das@FreeBSD.org> Subject: Re: cvs commit: src/sys/kern kern_sig.c Message-ID: <42277709.2070407@elischer.org> In-Reply-To: <4226B4EA.40308@freebsd.org> References: <200503021343.j22DhpQ3075008@repoman.freebsd.org> <200503020915.28512.jhb@FreeBSD.org> <4226446B.7020406@freebsd.org> <20050303033115.GA13174@VARK.MIT.EDU> <42269DB0.6070107@freebsd.org> <20050303052902.GA14011@VARK.MIT.EDU> <4226A46B.2090704@freebsd.org> <20050303060357.GA14180@VARK.MIT.EDU> <20050303001403.W811@odysseus.silby.com> <20050303064206.GA14434@VARK.MIT.EDU> <4226B4EA.40308@freebsd.org>
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David Xu wrote: > David Schultz wrote: > >> On Thu, Mar 03, 2005, Mike Silbersack wrote: >> >> >>> On Thu, 3 Mar 2005, David Schultz wrote: >>> >>> >>> >>>> Of course, there's another possible solution which is to remove >>>> the swapping code entirely. That would certainly simplify things, >>>> but it would also make FreeBSD degrade less gracefully under load. >>>> >>> >>> I don't think that would be a big loss; by the time you're doing a >>> lot of process swapping, you're pretty screwed. >>> >>> A process has to be swapped back in in order for it to be killed, >>> right? We might be better off without swapping, in that case. >>> >> >> >> Yeah, with 16K kernel stacks, you'd have to swap a lot of threads > 16K!! we used to run on 4k, and that was with interrupts using the stack as well.. now we a e not doing that.. we should look at stack usage and get it back to 8K at most! :-) (on x86) >> to make a big difference in the amount of wired memory in the >> system. KSE helps with this, because processes with thousands of >> user threads don't have thousands of kernel threads. >> >> >> > This only happens at comparative idle time, if the process is a heavy > I/O bound process, > this does not help. assuming that all those threads are doing IO. > >> Another thing that swapping does, though, is prevent some >> processes from running for a while when the system is under load, >> thereby reducing contention for resources and allowing the other >> processes to get things done. If people decide to go this way, it >> might be a good idea to keep the second feature. It costs very >> little in terms of complexity because no actual swapping is done. >> But who knows? Maybe nobody cares about this, either... >> >> >> > I would like to not swap out kernel stack, it allows me to write some > speedy code, > this is my personal favorit. :=) I think that swapping kernel stacks may be an idea who's time has passed.
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