From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 10 May 2002 03:03:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 10 May 2002 03:03:51 -0400 Received: from samba.sourceforge.net ([198.186.203.85]:22995 "HELO lists.samba.org") by vger.kernel.org with SMTP id ; Fri, 10 May 2002 03:03:50 -0400 Date: Fri, 10 May 2002 16:58:36 +1000 From: Anton Blanchard To: "Albert D. Cahalan" Cc: Robert Love , tchiwam , linux-kernel@vger.kernel.org, Rik van Riel , Gerrit Huizenga , Clifford White , oliendm@us.ibm.com Subject: Re: x86 question: Can a process have > 3GB memory? Message-ID: <20020510065836.GD17965@krispykreme> In-Reply-To: <1020980411.880.93.camel@summit> <200205092356.g49NuTS70861@saturn.cs.uml.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.3.28i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > Huh? Unless you mean ppc64, ppc is worse. > On a Mac, you get 2 GB of virtual memory per > process. You get up to 512 MB of physical memory > without highmem support, or usually 4 GB with > highmem support. This is fixed in recent kernels, you can specify it with a CONFIG option: # uname -a Linux 2.4.19-pre5 #185 Fri Apr 5 14:36:40 EST 2002 ppc # cat /proc/self/maps 0fea5000-0ffbb000 r-xp 00000000 03:0c 163581 /lib/libc-2.2.5.so 0ffbb000-0ffc5000 ---p 00116000 03:0c 163581 /lib/libc-2.2.5.so 0ffc5000-0ffeb000 rw-p 00110000 03:0c 163581 /lib/libc-2.2.5.so 0ffeb000-0fff0000 rw-p 00000000 00:00 0 10000000-10003000 r-xp 00000000 03:0c 1554092 /bin/cat 10012000-10013000 rw-p 00002000 03:0c 1554092 /bin/cat 10013000-10015000 rwxp 00000000 00:00 0 48000000-48014000 r-xp 00000000 03:0c 163537 /lib/ld-2.2.5.so 48014000-48015000 rw-p 00000000 00:00 0 48023000-48027000 rw-p 00013000 03:0c 163537 /lib/ld-2.2.5.so bfffe000-c0000000 rwxp fffff000 00:00 0 Of course on ppc64 kernels you have a full 4GB of userspace since the kernel sits at the top of the 64bit address space. > As with x86, the latest chips > offer a 36-bit (64 GB) physical address space. Paulus also has a hack that allows up to 15G of memory on POWER3 class machines although that isnt currently in the ppc32 tree. > That's not all! Linus recently singled out the PowerPC > MMU for a nice long abusive rant. :-) You get hashed > page tables. You get this: > > As with x86, segment registers map a 32-bit virtual > address space onto a larger one. The top 4 bits of > a 32-bit virtual address are used to select a segment, > and the segment provides 24 more address bits to > give you a 52-bit virtual address. Eeeew. This is all very well and good, put my ppc64 machine still outperforms anything out there on the kernel compile benchmark :) Anton