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 8D598C433EF for ; Tue, 22 Mar 2022 22:28:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238005AbiCVW3l convert rfc822-to-8bit (ORCPT ); Tue, 22 Mar 2022 18:29:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34650 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229780AbiCVW3d (ORCPT ); Tue, 22 Mar 2022 18:29:33 -0400 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 35A973878A for ; Tue, 22 Mar 2022 15:28:02 -0700 (PDT) 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-62-EXb9IYMXOCiR4--bAPJEbQ-1; Tue, 22 Mar 2022 22:27:59 +0000 X-MC-Unique: EXb9IYMXOCiR4--bAPJEbQ-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 15.0.1497.32; Tue, 22 Mar 2022 22:27:58 +0000 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.033; Tue, 22 Mar 2022 22:27:58 +0000 From: David Laight To: 'Jakub Kicinski' CC: 'Alexander Lobakin' , 'Wan Jiabing' , Jesse Brandeburg , "Tony Nguyen" , "David S. Miller" , Paolo Abeni , "intel-wired-lan@lists.osuosl.org" , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH v2] ice: use min_t() to make code cleaner in ice_gnss Thread-Topic: [PATCH v2] ice: use min_t() to make code cleaner in ice_gnss Thread-Index: AQHYPSxszwX/VYzTWUmJ1ZXJKTtOx6zJ/3twgAGw2QCAAAVpMIAABOQAgABC8EA= Date: Tue, 22 Mar 2022 22:27:58 +0000 Message-ID: References: <20220321135947.378250-1-wanjiabing@vivo.com> <20220322175038.2691665-1-alexandr.lobakin@intel.com> <20220322112730.482d674d@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> In-Reply-To: <20220322112730.482d674d@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> 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: Jakub Kicinski > Sent: 22 March 2022 18:28 > > On Tue, 22 Mar 2022 18:12:08 +0000 David Laight wrote: > > > > Oh FFS why is that u16? > > > > Don't do arithmetic on anything smaller than 'int' > > > > > > Any reasoning? I don't say it's good or bad, just want to hear your > > > arguments (disasms, perf and object code measurements) etc. > > > > Look at the object code on anything except x86. > > The compiler has to add instruction to mask the value > > (which is in a full sized register) down to 16 bits > > after every arithmetic operation. > > Isn't it also slower on some modern x86 CPUs? > I could have sworn someone mentioned that in the past. Not in the cpu clock count tables I've read. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)