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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 60047C38A2A for ; Sun, 10 May 2020 12:47:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4002D20820 for ; Sun, 10 May 2020 12:47:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728907AbgEJMrS convert rfc822-to-8bit (ORCPT ); Sun, 10 May 2020 08:47:18 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([146.101.78.151]:31193 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726863AbgEJMrR (ORCPT ); Sun, 10 May 2020 08:47:17 -0400 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-111-wTKvyRDLNUioeEmIP5t2pw-1; Sun, 10 May 2020 13:47:13 +0100 X-MC-Unique: wTKvyRDLNUioeEmIP5t2pw-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) by AcuMS.aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Sun, 10 May 2020 13:47:13 +0100 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Sun, 10 May 2020 13:47:13 +0100 From: David Laight To: 'Joe Perches' , Arnd Bergmann , "Oleksandr Natalenko" CC: "Jason A. Donenfeld" , LKML , X86 ML , Andrew Morton Subject: RE: [PATCH] Kconfig: default to CC_OPTIMIZE_FOR_PERFORMANCE_O3 for gcc >= 10 Thread-Topic: [PATCH] Kconfig: default to CC_OPTIMIZE_FOR_PERFORMANCE_O3 for gcc >= 10 Thread-Index: AQHWJUo8bK79Vz6Er0qWTasVui4yHqihRWbA Date: Sun, 10 May 2020 12:47:13 +0000 Message-ID: <9590a4674863448e8b13fee5086fcf73@AcuMS.aculab.com> References: <20200507224530.2993316-1-Jason@zx2c4.com> <20200508090202.7s3kcqpvpxx32syu@butterfly.localdomain> <20200508113336.2vdfdnc6tqyx4pu6@butterfly.localdomain> In-Reply-To: Accept-Language: en-GB, en-US Content-Language: 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 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Joe Perches > Sent: 08 May 2020 16:06 > On Fri, 2020-05-08 at 13:49 +0200, Arnd Bergmann wrote: > > Personally, I'm more interested in improving compile speed of the kernel > > Any opinion on precompiled header support? When ever I've been anywhere near it it is always a disaster. It may make sense for C++ where there is lots of complicated code to parse in .h files. Parsing C headers is usually easier. One this I have done that significantly speeds up .h file processing is to take the long list of '-I directory' parameters that are passed to the compiler and copy the first version of each file into a separate 'object headers' directory. This saves the compiler doing lots of 'failed opens'. If each fragment makefile lists its 'public' headers make can generate dependency rules that do the copies. FWIW make is much faster if you delete all the builtin and suffix rules and rely on explicit rules for each file. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)