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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D444CC433EF for ; Thu, 17 Feb 2022 13:36:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240983AbiBQNg2 convert rfc822-to-8bit (ORCPT ); Thu, 17 Feb 2022 08:36:28 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:43882 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234508AbiBQNgZ (ORCPT ); Thu, 17 Feb 2022 08:36:25 -0500 Received: from eu-smtp-delivery-151.mimecast.com (eu-smtp-delivery-151.mimecast.com [185.58.85.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 559902AF3C9 for ; Thu, 17 Feb 2022 05:36:10 -0800 (PST) Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id uk-mta-180-DvoA-mOvMgWZ2EaaUyzgIQ-1; Thu, 17 Feb 2022 13:36:07 +0000 X-MC-Unique: DvoA-mOvMgWZ2EaaUyzgIQ-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) by AcuMS.aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) with Microsoft SMTP Server (TLS) id 15.0.1497.28; Thu, 17 Feb 2022 13:36:06 +0000 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.028; Thu, 17 Feb 2022 13:36:06 +0000 From: David Laight To: 'Christophe Leroy' , "David S. Miller" , Jakub Kicinski CC: "netdev@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , "linux-kernel@vger.kernel.org" , "Masahiro Yamada" Subject: RE: [PATCH net v3] net: Force inlining of checksum functions in net/checksum.h Thread-Topic: [PATCH net v3] net: Force inlining of checksum functions in net/checksum.h Thread-Index: AQHYI/ioJk+yETn/QkyN152xjKaZ96yXvR4w Date: Thu, 17 Feb 2022 13:36:06 +0000 Message-ID: <35bcd5df0fb546008ff4043dbea68836@AcuMS.aculab.com> References: <978951d76d8cb84bab347c7623bc163e9a038452.1645100305.git.christophe.leroy@csgroup.eu> In-Reply-To: <978951d76d8cb84bab347c7623bc163e9a038452.1645100305.git.christophe.leroy@csgroup.eu> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Christophe Leroy > Sent: 17 February 2022 12:19 > > All functions defined as static inline in net/checksum.h are > meant to be inlined for performance reason. > > But since commit ac7c3e4ff401 ("compiler: enable > CONFIG_OPTIMIZE_INLINING forcibly") the compiler is allowed to > uninline functions when it wants. > > Fair enough in the general case, but for tiny performance critical > checksum helpers that's counter-productive. There isn't a real justification for allowing the compiler to 'not inline' functions in that commit. It rather seems backwards. The kernel sources don't really have anything marked 'inline' that shouldn't always be inlined. If there are any such functions they are few and far between. I've had enough trouble (elsewhere) getting gcc to inline static functions that are only called once. I ended up using 'always_inline'. (That is 4k of embedded object code that will be too slow if it ever spills a register to stack.) David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)