From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 509DEC433E0 for ; Wed, 3 Mar 2021 11:27:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F0D5660238 for ; Wed, 3 Mar 2021 11:27:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1357839AbhCCLYn (ORCPT ); Wed, 3 Mar 2021 06:24:43 -0500 Received: from smtprelay0018.hostedemail.com ([216.40.44.18]:46190 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S232490AbhCCCtC (ORCPT ); Tue, 2 Mar 2021 21:49:02 -0500 Received: from filter.hostedemail.com (clb03-v110.bra.tucows.net [216.40.38.60]) by smtprelay06.hostedemail.com (Postfix) with ESMTP id 42E2418225631; Wed, 3 Mar 2021 02:47:53 +0000 (UTC) X-Session-Marker: 6A6F6540706572636865732E636F6D X-HE-Tag: tin16_1602863276c1 X-Filterd-Recvd-Size: 2532 Received: from [192.168.1.159] (unknown [47.151.137.21]) (Authenticated sender: joe@perches.com) by omf07.hostedemail.com (Postfix) with ESMTPA; Wed, 3 Mar 2021 02:47:52 +0000 (UTC) Message-ID: <6b8b250a06a98ce42120a14824531a8641f5e8aa.camel@perches.com> Subject: Re: [Cocci] linux-kernel janitorial RFP: Mark static arrays as const From: Joe Perches To: Julia Lawall Cc: kernelnewbies , kernel-janitors , cocci , LKML Date: Tue, 02 Mar 2021 18:47:51 -0800 In-Reply-To: References: <053b06c47f08631675c295b5c893b90be4248347.camel@perches.com> Content-Type: text/plain; charset="ISO-8859-1" User-Agent: Evolution 3.38.1-1 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2021-03-02 at 22:41 +0100, Julia Lawall wrote: > > On Tue, 2 Mar 2021, Joe Perches wrote: > > > Here is a possible opportunity to reduce data usage in the kernel. > > Does it actually reduce data usage? Yes, at least for gcc. For instance: $ gcc --version gcc (Ubuntu 10.2.0-13ubuntu1) 10.2.0 And with the diff below (x86-64 defconfig with hwmon/pmbus and max20730) $ diff --git a/drivers/hwmon/pmbus/max20730.c b/drivers/hwmon/pmbus/max20730.c index 9dd3dd79bc18..b824eab95456 100644 --- a/drivers/hwmon/pmbus/max20730.c +++ b/drivers/hwmon/pmbus/max20730.c @@ -434,7 +434,7 @@ static long direct_to_val(u16 w, enum pmbus_sensor_classes > return d; } -static u32 max_current[][5] = { +static const u32 max_current[][5] = { [max20710] = { 6200, 8000, 9700, 11600 }, [max20730] = { 13000, 16600, 20100, 23600 }, [max20734] = { 21000, 27000, 32000, 38000 }, $ size drivers/hwmon/pmbus/max20730.o* text data bss dec hex filename 9245 256 0 9501 251d drivers/hwmon/pmbus/max20730.o.gcc.new 9149 352 0 9501 251d drivers/hwmon/pmbus/max20730.o.gcc.old with clang-11 it doesn't seem to make a difference: $ /usr/bin/clang --version Ubuntu clang version 11.0.0-2 $ size drivers/hwmon/pmbus/max20730.o* text data bss dec hex filename 9166 256 1 9423 24cf drivers/hwmon/pmbus/max20730.o.clang-11.new 9166 256 1 9423 24cf drivers/hwmon/pmbus/max20730.o.clang-11.old