From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp2f.orange.fr ([80.12.242.152]:46826 "EHLO smtp2f.orange.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752269AbXLNPiO convert rfc822-to-8bit (ORCPT ); Fri, 14 Dec 2007 10:38:14 -0500 Received: from me-wanadoo.net (localhost [127.0.0.1]) by mwinf2f27.orange.fr (SMTP Server) with ESMTP id 845BA700009C for ; Fri, 14 Dec 2007 16:38:12 +0100 (CET) Message-ID: <4762A35C.8020901@cosmosbay.com> Date: Fri, 14 Dec 2007 16:38:04 +0100 From: Eric Dumazet MIME-Version: 1.0 Subject: Re: RFC: remove __read_mostly References: <20071213222044.GH21616@stusta.de> <20071214152454.GR17536@waste.org> In-Reply-To: <20071214152454.GR17536@waste.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8BIT Sender: linux-arch-owner@vger.kernel.org List-ID: To: Matt Mackall Cc: Adrian Bunk , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org Matt Mackall a écrit : > 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? > > Yes, we probably can do something like that (in addition to !CONFIG_SMP)