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=-1.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 54216C47255 for ; Tue, 12 May 2020 01:10:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2C58920722 for ; Tue, 12 May 2020 01:10:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589245855; bh=K5pQ0hFUamxU3xDLOrlg3dPizqeqv2tllzaHsV47Xww=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=WdxNNLl2S5qp/XmxmX2rxU5RdkpppVxtX8PDPQTv4FvXF93vzac7L39/joDDRr53o bgJgtuVr7ODlZx2Ia/RWleub46swMBg2U8d1NG7o89PvYOmsqvkEpDXfS5UbxK2Vts zeICwU6SDKdRTKxLsgwaARKnlTQMZRQiDyVgP+tI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728465AbgELBKy (ORCPT ); Mon, 11 May 2020 21:10:54 -0400 Received: from conssluserg-02.nifty.com ([210.131.2.81]:36388 "EHLO conssluserg-02.nifty.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728105AbgELBKx (ORCPT ); Mon, 11 May 2020 21:10:53 -0400 Received: from mail-vk1-f173.google.com (mail-vk1-f173.google.com [209.85.221.173]) (authenticated) by conssluserg-02.nifty.com with ESMTP id 04C1AdSl006506 for ; Tue, 12 May 2020 10:10:39 +0900 DKIM-Filter: OpenDKIM Filter v2.10.3 conssluserg-02.nifty.com 04C1AdSl006506 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nifty.com; s=dec2015msa; t=1589245839; bh=K5pQ0hFUamxU3xDLOrlg3dPizqeqv2tllzaHsV47Xww=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=pa9iDFGLBXYgPJqDz/QwTqmPG5oekFgMxEK5JyH6ksenZrZAEtEdhBLH+SXhb6Dsy ygyfdGTlf7jEeHjtneblYz5GvSV13aqWmt9QUepF9Z3IQP3jhOBbZUPJSZ/z+7AU/o yQbnvjj9D9+OyuykgLRk/ZO+o0nGRvVRhyu5FXGpTWtbzJ07lRa2huXYVrlE7ka0Pm pmUFG+pfdHjskujX7BKkMCHfkE6le8qx+N7YEFf0IGDPoFuTc+88/bMS6yJM/RVRBj OD5anqGert/7P/TIoy7CX+F3S4Y1jKFgtfmpSvWuipT35MNHFAd0ovnmO00q/i16Ba ndjGtZGfWgujw== X-Nifty-SrcIP: [209.85.221.173] Received: by mail-vk1-f173.google.com with SMTP id j127so2882769vke.4 for ; Mon, 11 May 2020 18:10:39 -0700 (PDT) X-Gm-Message-State: AOAM530kaPS9mYOZ/Rz6zIlPXoCUU4RM7J5xOalbgQkRdnbrDm+r1bqL 5r1KDsTCHk/RGMRsvR2FS9bBbJsq5AGkW9v4MYI= X-Google-Smtp-Source: ABdhPJzT8cfk4Vw/UMZidHhfEFfI760psS+Z6D1KRvKDkAo0qESubVlXCPpQbhHvfSsFAJQX0r87/SXSJIIPLQXK5Ns= X-Received: by 2002:a1f:9093:: with SMTP id s141mr3699393vkd.96.1589245838591; Mon, 11 May 2020 18:10:38 -0700 (PDT) MIME-Version: 1.0 References: <20200507224530.2993316-1-Jason@zx2c4.com> <20200508090202.7s3kcqpvpxx32syu@butterfly.localdomain> <20200508113336.2vdfdnc6tqyx4pu6@butterfly.localdomain> <9590a4674863448e8b13fee5086fcf73@AcuMS.aculab.com> In-Reply-To: <9590a4674863448e8b13fee5086fcf73@AcuMS.aculab.com> From: Masahiro Yamada Date: Tue, 12 May 2020 10:10:02 +0900 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] Kconfig: default to CC_OPTIMIZE_FOR_PERFORMANCE_O3 for gcc >= 10 To: David Laight Cc: Joe Perches , Arnd Bergmann , Oleksandr Natalenko , "Jason A. Donenfeld" , LKML , X86 ML , Andrew Morton Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, May 10, 2020 at 9:47 PM David Laight wrote: > > 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. Kbuild disables Make's builtin rules at least. # Do not use make's built-in rules and variables # (this increases performance and avoids hard-to-debug behaviour) MAKEFLAGS += -rR -- Best Regards Masahiro Yamada