From owner-svn-src-head@FreeBSD.ORG Thu Nov 1 14:05:46 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 D0E9FB7B; Thu, 1 Nov 2012 14:05:46 +0000 (UTC) (envelope-from asmrookie@gmail.com) Received: from mail-lb0-f182.google.com (mail-lb0-f182.google.com [209.85.217.182]) by mx1.freebsd.org (Postfix) with ESMTP id AC17B8FC12; Thu, 1 Nov 2012 14:05:45 +0000 (UTC) Received: by mail-lb0-f182.google.com with SMTP id b5so2366193lbd.13 for ; Thu, 01 Nov 2012 07:05:44 -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=q4TqSL0uQbxwJnLq3zAQOChNaWRVD5OeOkbccO3a5Bk=; b=qyoNWe4a0y1Qn7dHefuBb+xaCKE37ug9XBDet6o2ATu24KLA7H6hzOmYk3bQvCIQyW 8O/28ThgpRJ0+GYD6a6i/nP7ZqK3G/t6U96m4bpgwqOsxNz05NS5a46aDcaIKBIjSpg9 W9b/NiXnbyoLrsKF/aIUoAuQZYWcWUki0x7um1EZp28S1pb5odCcJEMGczHZKeGBzlzx A1uRZ9MklXTKjhEKOsV/mGm2IjZdzLbYKpbwUZ8lFkjf1nSPaTUk85Jc2mAqwqszTIo0 dWVLABaetM3zoZXdrSbn5QCTMtSUnJqJfagXP8IpBrnJ+MhF6NtHFD/WaVjCR0i/wXjC 1Sjw== MIME-Version: 1.0 Received: by 10.152.110.234 with SMTP id id10mr14865643lab.15.1351778744194; Thu, 01 Nov 2012 07:05:44 -0700 (PDT) Sender: asmrookie@gmail.com Received: by 10.112.30.37 with HTTP; Thu, 1 Nov 2012 07:05:44 -0700 (PDT) In-Reply-To: <1351778472.1120.117.camel@revolution.hippie.lan> 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 14:05:44 +0000 X-Google-Sender-Auth: S8VdgtNcY-MpZHkRpLVXMncOh80 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 14:05:46 -0000 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? CACHE_LINE_SIZE must not change during a STABLE release lifetime, of course, for the same arch. Attilio -- Peace can only be achieved by understanding - A. Einstein