From owner-freebsd-hackers Fri Aug 1 14:50:49 1997 Return-Path: Received: (from root@localhost) by hub.freebsd.org (8.8.5/8.8.5) id OAA14353 for hackers-outgoing; Fri, 1 Aug 1997 14:50:49 -0700 (PDT) Received: from jenolan.rutgers.edu (davem@jenolan.rutgers.edu [128.6.111.5]) by hub.freebsd.org (8.8.5/8.8.5) with ESMTP id OAA14348 for ; Fri, 1 Aug 1997 14:50:47 -0700 (PDT) Received: (from davem@localhost) by jenolan.rutgers.edu (8.8.5/8.8.5) id RAA03675; Fri, 1 Aug 1997 17:50:03 -0400 Date: Fri, 1 Aug 1997 17:50:03 -0400 Message-Id: <199708012150.RAA03675@jenolan.rutgers.edu> From: "David S. Miller" To: toor@dyson.iquest.net CC: Shimon@i-connect.net, FreeBSD-Hackers@FreeBSD.ORG In-reply-to: <199708012118.QAA05888@dyson.iquest.net> (toor@dyson.iquest.net) Subject: Re: Kernel howto, Second Request Sender: owner-freebsd-hackers@FreeBSD.ORG X-Loop: FreeBSD.org Precedence: bulk From: "John S. Dyson" Date: Fri, 1 Aug 1997 16:18:33 -0500 (EST) Unlike certain (broken) systems, FreeBSD doesn't map all of phys memory by default. This of course, saves address space for user processes, and keeps physical memory size from being constrained by kernel space limitations. Yes, but please do not ignore the fact that on modern architectures (read as: 64-bit) it lacks any these limitations. (for example, on the UltraSparc under Linux, the full 64-bit virtual address space is given to the user, and arbitrarily large physical memory configurations are supported, all this is done at zero cost, and it's possible to be zero cost because of this "broken" system's design). Not to mention the fact that in many cases it also makes SMP cheaper (Linux only performs tlb flush cross calls during swapping, ptrace(), and for user threads). Later, David "Sparc" Miller davem@caip.rutgers.edu