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Path: euryale.cc.adfa.oz.au!newshost.carno.net.au!harbinger.cc.monash.edu.au!nntp.coast.net!howland.erols.net!newsfeed.internetmci.com!newsfeed.direct.ca!nntp.portal.ca!van-bc!n1van.istar!van.istar!west.istar!ott.istar!istar.net!gateway.qnx.com!not-for-mail From: doug@qnx.com (Doug Santry) Newsgroups: comp.unix.bsd.freebsd.misc Subject: Re: Embedded FreeBSD Date: 22 Jan 1997 16:05:13 -0500 Organization: QNX Software Systems Lines: 66 Message-ID: <5c5ve9$hls@qnx.com> References: <32B744C0.2DA9@wdc.net> <5c14ih$7nn@uriah.heep.sax.de> <5c2kub$6uu@qnx.com> <5c3h41$mtn@uriah.heep.sax.de> NNTP-Posting-Host: qnx.com Xref: euryale.cc.adfa.oz.au comp.unix.bsd.freebsd.misc:34371 In article <5c3h41$mtn@uriah.heep.sax.de>, J Wunsch <joerg_wunsch@uriah.heep.sax.de> wrote: >doug@qnx.com (Doug Santry) wrote: > >> BSD is bigger than a meg. With a 16 meg machine it swaps(running >> X). The same setup on QNX has megs of free memory. > >That surprises me a little. For a machine running X11, it's not the >kernel but the applications that usually waste the memory, and they >shouldn't be that much different in size for the same architecture. > >Of course, if you're using a window system that is not X11, that's a >different thing. For some reason, our Mach64 X server is half the size of the XFree86 one. > >> >Never trust an operating system you don't have sources for. ;-) >> >> ya ya :-) > >Sure, but this .sig is not tailored to QNX. ;) I used to have it for >more than a year now, so it's really a `signature', not just an >opinion only... I know, I've seen your sig here for ages, I just thought it was funny considering what we started talking about. :) >> Never trust an operating system with a kernel bigger than 32k! ;-) > >That's unfair when comparing a microkernel OS, however. You have to Hence the smiley! >at least account for those processes that perform kernel functionality >in a monolithic kernel world. Though i have no doubts that it won't >be much more than 200...300 KB in QNX. Well, once we have the network stuff, socket interface and TCP stack going we start using around 700k code and data. >OTOH, memory is cheap, we aren't running a PDP-11 with hand-wired core >memory. I still feel much more comfortable to get a ``blahblah sd0 >blah UNIT ATTENTION: Bus-device reset, device reset, or power-on >reset'' instead of just being faced with ``ASC(Q): 29,0'', even though >i realize that this collection of strings accounts for some KB of the >mentioned general bloat. >What we sorely need, looking from the monolith-kernel point of view, >is pageable kernel memory. While this doesn't solve the real-time >problems (so we are heavily diverging from the subject now), it might >help against the waste of physical memory on small machines. Disks >are even cheaper than memory these days (though the ratio is not that >drastic as it used to be in the PDP-11 era). Why bother. BSD is a general purpose desktop OS. RAM is flowing in the streets. It really doesn't concern me that much. The effort required to make the kernel pageable isn't worth it. The effort could be put into something else more important. Like asynchronous system calls, or user level pathname registration(more powerful than the portal filesystem). Maybe even the ability to attach a file descriptor to another process. There are some really cool abstractions that could be implemented that would be easier and have a higher payoff than a pageable kernel. DJS