From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from waste.org ([66.93.16.53]:50093 "EHLO waste.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753124AbXLNPZJ (ORCPT ); Fri, 14 Dec 2007 10:25:09 -0500 Date: Fri, 14 Dec 2007 09:24:55 -0600 From: Matt Mackall Subject: Re: RFC: remove __read_mostly Message-ID: <20071214152454.GR17536@waste.org> References: <20071213222044.GH21616@stusta.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20071213222044.GH21616@stusta.de> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Adrian Bunk Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org On Thu, Dec 13, 2007 at 11:20:44PM +0100, Adrian Bunk wrote: > I tried the following patch with a full x86 .config [1]: > > --- a/include/asm-x86/cache.h > +++ b/include/asm-x86/cache.h > -#define __read_mostly __attribute__((__section__(".data.read_mostly"))) > +/* #define __read_mostly __attribute__((__section__(".data.read_mostly"))) */ > > The result [2,3] was: > > -rwxrwxr-x 1 bunk bunk 46607243 2007-12-13 19:50 vmlinux.old > -rwxrwxr-x 1 bunk bunk 46598691 2007-12-13 21:55 vmlinux > > It's not a surprise that the kernel can become bigger when __read_mostly > gets used, especially in cases where __read_mostly prevents gcc > optimizations. > > My question is: > Is there anywhere in the kernel a case where __read_mostly brings a > measurable improvement or can it be removed? Yes, but perhaps we can put it under CONFIG_BASE_FULL? -- Mathematics is the supreme nostalgia of our time.