From owner-svn-src-head@FreeBSD.ORG Thu Nov 1 14:07:03 2012 Return-Path: Delivered-To: svn-src-head@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 51C19CA7; Thu, 1 Nov 2012 14:07:03 +0000 (UTC) (envelope-from asmrookie@gmail.com) Received: from mail-la0-f54.google.com (mail-la0-f54.google.com [209.85.215.54]) by mx1.freebsd.org (Postfix) with ESMTP id 213D38FC18; Thu, 1 Nov 2012 14:07:01 +0000 (UTC) Received: by mail-la0-f54.google.com with SMTP id e12so2341011lag.13 for ; Thu, 01 Nov 2012 07:07:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:reply-to:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type; bh=ZbvoZVD6PoGVODhVgoXDU2WloSSzpIDTKx/J3sMmeRQ=; b=uhuhg+fIDYhyb69kCP6qRyqaEwCrfAdF7E2KlrktCJc1GAQoMzag/vq284AyAg8lxz IxAeHnosXsJWVGqp1WvYLNIAuiOOj2qpUpB63ZRnLMDs+mJO2EKlvu0rLtrM/c5XNFoE iKfW2Te1QMi8gfeTHLfWantNpJPk34K+vAMZ0y25PL2Z1Jhmzvx7D5eOM3mdwsVwvS8F uA0e+4r7+3RFDg6WWuuCOAsHdYF2OvPAIzFUAuWDCvi6TfbfdAYqDGOC1rAk73LSwjsj 2jsPAIhmn9WHQmLwI+HmNGQWS0osxA4WQLW7z3Svu+NfphAAh93nGEkc06YXBgElbL01 u42A== MIME-Version: 1.0 Received: by 10.112.47.129 with SMTP id d1mr15818957lbn.115.1351778820698; Thu, 01 Nov 2012 07:07:00 -0700 (PDT) Sender: asmrookie@gmail.com Received: by 10.112.30.37 with HTTP; Thu, 1 Nov 2012 07:07:00 -0700 (PDT) In-Reply-To: References: <201210311807.q9VI7IcX000993@svn.freebsd.org> <1351707964.1120.97.camel@revolution.hippie.lan> <20121101100814.GB70741@FreeBSD.org> <1351778472.1120.117.camel@revolution.hippie.lan> Date: Thu, 1 Nov 2012 14:07:00 +0000 X-Google-Sender-Auth: 1N0fgANgwHO93Zd9D8cNYmnQPJs Message-ID: Subject: Re: svn commit: r242402 - in head/sys: kern vm From: Attilio Rao To: Ian Lepore Content-Type: text/plain; charset=UTF-8 Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, Gleb Smirnoff , src-committers@freebsd.org X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list Reply-To: attilio@FreeBSD.org 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: Thu, 01 Nov 2012 14:07:03 -0000 On Thu, Nov 1, 2012 at 2:05 PM, Attilio Rao wrote: > On Thu, Nov 1, 2012 at 2:01 PM, Ian Lepore > wrote: >> On Thu, 2012-11-01 at 10:42 +0000, Attilio Rao wrote: >>> On 11/1/12, Gleb Smirnoff wrote: >>> > On Wed, Oct 31, 2012 at 06:33:51PM +0000, Attilio Rao wrote: >>> > A> > Doesn't this padding to cache line size only help x86 processors in an >>> > A> > SMP kernel? I was expecting to see some #ifdef SMP so that we don't >>> > pay >>> > A> > a big price for no gain in small-memory ARM systems and such. But >>> > maybe >>> > A> > I'm misunderstanding the reason for the padding. >>> > A> >>> > A> I didn't want to do this because this would be meaning that SMP option >>> > A> may become a completely killer for modules/kernel ABI compatibility. >>> > >>> > Do we support loading non-SMP modules on SMP kernel and vice versa? >>> >>> Actually that's my point, we do. >>> >>> Attilio >>> >>> >> >> Well we've got other similar problems lurking then. What about a module >> compiled on an arm system that had #define CACHE_LINE_SIZE 32 and then >> it gets run on a different arm system whose kernel is compiled with >> #define CACHE_LINE_SIZE 64? > > That should not happen. Is that a real case where you build a module > for an ARM family and want to run against a kernel compiled for > another? Besides that, the ARM CACHE_LINE_SIZE is defined in the shared headers so there is no way this can be a problem. Attilio -- Peace can only be achieved by understanding - A. Einstein