From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Thu, 05 Nov 2009 09:44:26 +0100 (CET) Received: from localhost.localdomain ([127.0.0.1]:43631 "EHLO h5.dl5rb.org.uk" rhost-flags-OK-OK-OK-FAIL) by ftp.linux-mips.org with ESMTP id S1492050AbZKEIoX (ORCPT ); Thu, 5 Nov 2009 09:44:23 +0100 Received: from h5.dl5rb.org.uk (localhost.localdomain [127.0.0.1]) by h5.dl5rb.org.uk (8.14.3/8.14.3) with ESMTP id nA58jhpY014154; Thu, 5 Nov 2009 09:45:44 +0100 Received: (from ralf@localhost) by h5.dl5rb.org.uk (8.14.3/8.14.3/Submit) id nA58jbUT014148; Thu, 5 Nov 2009 09:45:37 +0100 Date: Thu, 5 Nov 2009 09:45:37 +0100 From: Ralf Baechle To: Wu Zhangjin Cc: Arnaud Patard , linux-mips@linux-mips.org, LKML , huhb@lemote.com, yanh@lemote.com, Zhang Le , Thomas Gleixner , Nicholas Mc Guire , zhangfx@lemote.com, liujl@lemote.com Subject: Re: [PATCH -queue v0 1/6] [loongson] add basic loongson-2f support Message-ID: <20091105084537.GA12582@linux-mips.org> References: <1257332652.8716.5.camel@falcon.domain.org> <20091104111957.GA13549@linux-mips.org> <1257348226.16033.4.camel@falcon.domain.org> <20091104201520.GA26504@linux-mips.org> <1257385176.16033.17.camel@falcon.domain.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1257385176.16033.17.camel@falcon.domain.org> User-Agent: Mutt/1.5.19 (2009-01-05) Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 24692 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: ralf@linux-mips.org Precedence: bulk X-list: linux-mips On Thu, Nov 05, 2009 at 09:39:36AM +0800, Wu Zhangjin wrote: > > > > We have other systems where 32-bit kernel support is just remarkably ugly. > > > > We've dropped 32-bit support for the SGI IP32 aka O2 - nobody seems to even > > > > have really noticed that. The Sibyte systems would be good candidates to do > > > > the same as accesses to outside the 32-bit address space are needed very > > > > frequently. > > > > > > > > > > So, we really remove the 32bit support? > > > > > > 1312 config CPU_LOONGSON2 > > > 1313 bool > > > 1314 select CPU_SUPPORTS_32BIT_KERNEL --> remove it? > > > 1315 select CPU_SUPPORTS_64BIT_KERNEL > > > 1316 select CPU_SUPPORTS_HIGHMEM > > > > > > If you all agree, I will send a new patch to remove the above line and > > > resend the corresponding patches without 32bit support, and removed the > > > relative CONFIG_64BIT lines in the patches too. > > > > If you need highmem with 32-bit (and with Loongson systems I assume that > > virtually all systems will have enough RAM to require that) then you're > > almost certainly better off going 64-bit. Highmem takes a performance toll > > which for some workloads can be very significant. And while highmem won't > > go away any time soon it's nothing kernel performance is being tuned for, > > so it's only going to get worse into the future so I'd not waste time on > > highmem unless I have to. > > > > What I have mentioned: "perhaps some guys need the 32bit version" here > means, perhaps some embedded systems without enough memory and enough > storage space may need the 32bit version, they not need highmem and > also, the 32bit version will save some storage space for them. and I > have used the 32bit version on my box and notebook(of course, only for > experiments), no obvious problems. > > Reserve the 32bit version as an choice and select 64bit by default in > the default config file? No problem - I was just expressing my expressing my experiences on the usefulness of supporting both settings. One usually tends up favored, the other little used. Ralf