Date: Thu, 2 Aug 2001 15:30:17 -0300 (BRST) From: Rik van Riel <riel@conectiva.com.br> To: Julian Elischer <julian@elischer.org> Cc: Terry Lambert <tlambert2@mindspring.com>, craig <craiglei@pasia.com.cn>, <freebsd-hackers@FreeBSD.ORG> Subject: Re: How to visit physical memory above 4G? Message-ID: <Pine.LNX.4.33L.0108021528520.5582-100000@duckman.distro.conectiva> In-Reply-To: <Pine.BSF.4.21.0108021325410.41008-100000@InterJet.elischer.org>
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On Thu, 2 Aug 2001, Julian Elischer wrote: > On Thu, 2 Aug 2001, Rik van Riel wrote: > > > > On the really large machines, this can lead to the > > situation where even the page tables hardly fit into > > KVA. 4MB pages seem like the only solution ... > > There is no reason why we need to keep the kernel and the user > process in the same 4GB map except for efficiency. > > There have been many UNIX machines in the past which put them in > separate virtual spaces That was on machines where the CPU could actually address two separate spaces at once, right ? (like eg. m68k) > The kernel would haev 4GB for itself and each process would have 4BG. > > System calls would be come more expensive as each would require > a full page-table swap and a TLB flush. > However it might be worth it for some people. Interrupt handling would also require a full page table swap and TLB flush. Considering that, I think the number of people for whom this will be worth it has probably dropped a bit ;) Rik -- Executive summary of a recent Microsoft press release: "we are concerned about the GNU General Public License (GPL)" http://www.surriel.com/ http://www.conectiva.com/ http://distro.conectiva.com/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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