From owner-svn-src-head@freebsd.org Sat Mar 4 21:13:48 2017 Return-Path: Delivered-To: svn-src-head@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 1C2CBCF51F9 for ; Sat, 4 Mar 2017 21:13:48 +0000 (UTC) (envelope-from ian@freebsd.org) Received: from outbound1a.eu.mailhop.org (outbound1a.eu.mailhop.org [52.58.109.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id A1ED81B4B for ; Sat, 4 Mar 2017 21:13:47 +0000 (UTC) (envelope-from ian@freebsd.org) X-MHO-User: 73b211bc-011f-11e7-95b5-6dfd7dbb0ee5 X-Report-Abuse-To: https://support.duocircle.com/support/solutions/articles/5000540958-duocircle-standard-smtp-abuse-information X-Originating-IP: 73.78.92.27 X-Mail-Handler: DuoCircle Outbound SMTP Received: from ilsoft.org (unknown [73.78.92.27]) by outbound1.eu.mailhop.org (Halon) with ESMTPSA id 73b211bc-011f-11e7-95b5-6dfd7dbb0ee5; Sat, 04 Mar 2017 21:13:46 +0000 (UTC) Received: from rev (rev [172.22.42.240]) by ilsoft.org (8.15.2/8.15.2) with ESMTP id v24LDarL004747; Sat, 4 Mar 2017 14:13:36 -0700 (MST) (envelope-from ian@freebsd.org) Message-ID: <1488662016.69705.21.camel@freebsd.org> Subject: Re: svn commit: r314669 - head/sys/i386/conf From: Ian Lepore To: Pedro Giffuni , John Baldwin Cc: Slawa Olhovchenkov , src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Date: Sat, 04 Mar 2017 14:13:36 -0700 In-Reply-To: References: <201703041504.v24F4HMh023937@repo.freebsd.org> <20170304153228.GM15630@zxy.spb.ru> <2368011.hGEX4V32U5@ralph.baldwin.cx> Content-Type: text/plain; charset="iso-8859-13" X-Mailer: Evolution 3.18.5.1 FreeBSD GNOME Team Port Mime-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 04 Mar 2017 21:13:48 -0000 On Sat, 2017-03-04 at 15:49 -0500, Pedro Giffuni wrote: > > > > Il giorno 04 mar 2017, alle ore 14:43, John Baldwin > g> ha scritto: > > > > On Saturday, March 04, 2017 10:52:46 AM Pedro Giffuni wrote: > > > > > > > > > On 03/04/17 10:32, Slawa Olhovchenkov wrote: > > > > > > > > On Sat, Mar 04, 2017 at 03:04:17PM +0000, Pedro F. Giffuni > > > > wrote: > > > > > > > > > > > > > > Author: pfg > > > > > Date: Sat Mar  4 15:04:17 2017 > > > > > New Revision: 314669 > > > > > URL: https://svnweb.freebsd.org/changeset/base/314669 > > > > > > > > > > Log: > > > > >  Drop i486 from the default i386 GENERIC kernel > > > > > configuration. > > > > > > > > > >  80486 production was stopped by Intel on September 2007. > > > > > Dropping the 486 > > > > >  configuration option from the GENERIC kernel improves > > > > > performance > > > > >  slightly. > > > > > > > > > >  Removing I486_CPU is consistent at this time: we don't > > > > > support any > > > > >  processor without a FPU and the PC-98 arch, which frequently > > > > > involved i486 > > > > >  CPUs, is also gone so we don't test such platforms anymore. > > > > What is realy mean? > > > This means we don't do work-arounds that would be required for > > > raw 486. > > > Instead we will use the 586 instructions by default. > > This doesn't change that.  The kernel already has runtime tests in > > place > > for new things on 486 and later via cpuid. > > > Hmm ..then I am wondering if I effectively changed anything? > > > > > > > > > > > > > > Some Via CPU is like i486 (by instruction set). > > > > > > > > CPU: VIA Ezra (800.04-MHz 686-class CPU) > > > >  Origin="CentaurHauls"  Id=0x678  Family=0x6  Model=0x7  Steppi > > > > ng=8 > > > >  Features=0x803035 > > > >  AMD Features=0x80000000<3DNow!> > > > > > > > 486 never had MMX extensions. > > > This is a 686, performance should improve ~4%. > > How did you measure the improvement?  Keeping I486_CPU doesn't > > really > > do anything except remove a some #ifdef'd conditionals in > > identcpu.c > > and initcpu.c.  It doesn't affect whether we use the TSC, MMX, > > etc.  Those > > are all runtime checks based the CPU feature flags from cpuid. > > > The number came out from an old posting involving buildworld times, > which I can˙t find now :(. > Things seem to have changed a lot: it was surely using GCC back then, > I don˙t believe clang does much distinction about 486 at all. > > BTW, does it make sense to keep i586 in the configuration still? Both > i486 and i586 were once removed but later re-instated in r205336. > > Pedro. i586 hardware which is not also i686 is still alive and well, but I think at this point it's mostly used in specialized applications.  I have no problem with removing i586 from GENERIC, but please don't remove underlying support for setting it in custom kernel configs. -- Ian