Date: Sun, 6 Oct 2002 19:48:40 -0700 (PDT) From: Nate Lawson <nate@root.org> To: freebsd-arch@FreeBSD.ORG Cc: freebsd-smp@FreeBSD.ORG Subject: Re: Running independent kernel instances on dual-Xeon/E7500 system Message-ID: <Pine.BSF.4.21.0210061941060.5534-100000@root.org> In-Reply-To: <20021006115816.A28963@darkstar.gte.net>
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Sorry for the unhelpful first posting. I sent a more detailed letter via private mail, recommending he look into the exokernel papers. My dismissiveness was due to anticipating the direction this was going, which is nicely shown by the response below. In short, dedicated processors for IO were used in the minicomputer days but are wasteful nowadays when you have lightweight interrupts and/or polling when appropriate. If your scheduler sucks, fix it. If a device needs extra processing equivalent to another N Ghz CPU, the vendor will add silicon. The "S" in SMP is for symmetric, lest we forget. -Nate On Sun, 6 Oct 2002, Robert Clark wrote: > I've often thought it would be nice to be able to devote > one processor to a RT style OS instance that continuous > duty doing "throw away" work updating the display, audio, > etc. > > Using a general purpose CPU for graphics and sound work > may not result in the kinds of performance you get with > a GPU, but I have to imagine it would have a better > chance of encouraging "free" driver development. > > On the flip side, the OS instance that didn't have > anything to do with audio/video could spend more of > its time doing network/disk I/O, and more traditional > duties. > > [RC] > > On Sat, Oct 05, 2002 at 02:28:04AM -0700, Terry Lambert wrote: > > Nate Lawson wrote: > > > On Fri, 4 Oct 2002, David Francheski wrote: > > > > I have a dual-Xeon processor (with E7500 chipset) motherboard. > > > > Can anybody tell me what the development effort would be to > > > > boot and run two independent copies of the FreeBSD kernel, > > > > one on each Xeon processor? By this I mean that an SMP > > > > enabled kernel would not be utilized, each kernel would be UP. > > > > > > > > Regards, > > > > David L. Francheski > > > > > > Not possible without another BIOS, PCI bus, and separate memory -- > > > i.e. another PC. > > > > IPL'ing is not the same as "running". So long as you crafted the > > memory image of the second OS and its page tables, etc., using the > > first processor, there should be no problem running a second copy > > of an OS on an AP, as a result of a START IPI from the BP, after > > the code is crafted. Thus there is no need for a separate BIOS. > > > > <snip> > > > -- > > > > I've personally considered pursuing the ability to run code seperately, > > though with the same 4G address space, seperated, so as to permit > > running a debugger against a "crashed" FreeBSD "system" running on an > > AP, doing the debugging from the BP, as a hosted system. The cost > > in labor would be 2-3 months of continuous work, I think... that is > > the estimate I arrived at, when I considered the project previously. > > Doing this certaily beats the cost of buying an ICE to get similar > > capability. > > > > > > It would be interesting to see what other people have to say on this, > > other than "can't be done" (not to pick on you in particular, here; > > this is the knee-jerk reaction many people have to things like this). > > > > -- Terry > > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > > with "unsubscribe freebsd-smp" in the body of the message > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-arch" in the body of the message > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-smp" in the body of the message
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