Date: Thu, 5 Oct 2000 17:06:19 -0700 (PDT) From: Matthew Jacob <mjacob@feral.com> To: Terry Lambert <tlambert@primenet.com> Cc: Wilko Bulte <wkb@freebie.demon.nl>, Doug Rabson <dfr@nlsystems.com>, FreeBSD-alpha mailing list <freebsd-alpha@FreeBSD.ORG> Subject: Re: max memory on Alpha? Message-ID: <Pine.BSF.4.21.0010051704270.62475-100000@beppo.feral.com> In-Reply-To: <200010052209.PAA16408@usr05.primenet.com>
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On Thu, 5 Oct 2000, Terry Lambert wrote: > > > Do you know *if* there is a hard limit at 2Gb? > > > > I don't think there is a *hard* limit for the basic VM system but I > > imagine it might have problems finding a large enough contiguous region to > > map the vm_page_t structures. The main limitation is in the i/o system as > > previously noted. > > It seems to me that the contiguity requirement is bogus. > > If contiguity is other than an implementation artificat (i.e. > it is a true hardware requirement), then it seems to me that > it is time to provide a mechanism for defragging KVA space, > or place the vm_page_t structures in a seperate virtual > address space. Physical page contiguity should not be a requirement- but this is may just be an implementation cleverness issue. > > On a related note, I've always though that drivers (and their > related kernel threads, should such obnoxious things become > more commonplace) ought to run in their own VA space, on a > per driver basis, so that a bad driver couldn't pee in the > pool. This would keep bad drivers from actually crashing > the system, short of a halt or going into a tight loop (even > then, a timer interrupt should be able to recover the halt, > and a preemption should be able to recover the loop, if it > is a kernel thread -- or even generally, if kernel preemption > were to be supported). > This makes no sense for anything but a system that has an IOMMU - unless I've totally misunderstood you. -matt To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-alpha" in the body of the message
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