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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 0D4BFC4338F for ; Wed, 18 Aug 2021 18:29:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D52FB60E90 for ; Wed, 18 Aug 2021 18:29:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232365AbhHRS3x (ORCPT ); Wed, 18 Aug 2021 14:29:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50038 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229448AbhHRS3v (ORCPT ); Wed, 18 Aug 2021 14:29:51 -0400 Received: from mout-p-201.mailbox.org (mout-p-201.mailbox.org [IPv6:2001:67c:2050::465:201]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7EF65C061764 for ; Wed, 18 Aug 2021 11:29:16 -0700 (PDT) Received: from smtp2.mailbox.org (smtp2.mailbox.org [IPv6:2001:67c:2050:105:465:1:2:0]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-384) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mout-p-201.mailbox.org (Postfix) with ESMTPS id 4Gqbyf5wZdzQkj1; Wed, 18 Aug 2021 20:29:14 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=mailbox.org; h= content-transfer-encoding:content-language:content-type :content-type:in-reply-to:mime-version:date:date:message-id:from :from:references:subject:subject:received; s=mail20150812; t= 1629311351; bh=8yFvBMUga1EVpv+SYC9LNVr5Eqe0h/P1ceZIwCgztko=; b=H hs1DQWIWzQpPNrWc4uZDBALlXRB2UfeUCeS7pwpRXEXQ4v12/XxQe1ob8fGvZRIx swsVdx0M5ZTYYYZEHcU1dxxM0/+W0cIK7GN0OUVXpvkMD+Dlhr5xWXUMtRPtJ17J B8Q5fE7ErRU4szS4z03dqKtxB/XWJH5ZmX50zNG1AESKmT9eSeT6NnTwTpdWNxse iGjTj7HlHUaWjRZnEFHqIpNMlxhSWwiYdQ7icJiudtBxidqPIw6NEvgum+oPwtOQ 1tzc4tPHwnEsbHI01Yj5k8vfMU2+OvToSYhRCM6x/uHtOiOFUkspzzEM0yCTOI36 ETI2+S9z6ss4zbBLPQTkA== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mailbox.org; s=mail20150812; t=1629311353; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=w5sdReL5aVMcQw1mZdSVeTxvGoot/SnqNO7EPVVP9pM=; b=KsPfb/oJRLypSlQq1BqBLXOXbp2JrqappFzk0Aq6wYVUZWzm+lGDV21sNMsU5cbHM7qc7w dioyCpdCcpN7OWRevU2s+b6kjNyYXQ5IO72um0YkhhatVTU08S06zs4M3nCTOSQFK9+Il/ Apm4e/Ghs5icspd1fpISLEHK8pf7p1S2nzU0VFbblGMawNzpyHhEME56qQMGpJhQqqYUgw hNBoNBXEemZSHRIMo1bUxWn7RCchZ5Lbrjp7UNQ9n4vZmeC8tYkUj4nCl1tnR4Q+AnxAjI ufC5J4g51WB9eot+zddTi2t00DI5snCkK/GikrpLb5qfeJMOea9/3cyvpDj+hQ== X-Virus-Scanned: amavisd-new at heinlein-support.de Received: from smtp2.mailbox.org ([80.241.60.241]) by spamfilter06.heinlein-hosting.de (spamfilter06.heinlein-hosting.de [80.241.56.125]) (amavisd-new, port 10030) with ESMTP id VlfYjx7ppfLM; Wed, 18 Aug 2021 20:29:11 +0200 (CEST) Subject: Re: [PATCH 2/2] x86, Makefile: Add new generic x86-64 settings v2/v3/v4 To: Borislav Petkov Cc: "linux-kernel@vger.kernel.org" , "x86@kernel.org" , "clang-built-linux@googlegroups.com" , "graysky@archlinux.us" , "masahiroy@kernel.org" , Christoph Hellwig References: <269701460.117528.1629210189833@office.mailbox.org> <796036867.117557.1629210288168@office.mailbox.org> <1708009975.124311.1629299321026@office.mailbox.org> From: Tor Vic Message-ID: <25f1e81a-84f7-e63c-2989-cd4fddd695e7@mailbox.org> Date: Wed, 18 Aug 2021 18:28:47 +0000 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: DC5BD1813 X-Rspamd-UID: 643fc7 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 18.08.21 17:59, Borislav Petkov wrote: > On Wed, Aug 18, 2021 at 05:08:40PM +0200, torvic9@mailbox.org wrote: >> I ran some quick checks and benchmarks, and your doubts seem to be >> justified. A 5.14-rc6 kernel compiled with the default 'generic' and >> one built with 'x86-64-v3' even have the exact same uncompressed file >> size. Benchmarks were inconclusive as well. > > Lemme preface this with a IMHO: > > Yeah, those -march machine-specific compiler switches don't really > show any perf improvements for kernels because, well, if you look at > the instruction stream a kernel executes, there's not really a whole > lot left to optimize after -O2. > > Also, the percentage of time a machine spends in the kernel should be a > lot smaller (orders of magnitude) than in userspace - the operative word > being *should* here :-) - so there really isn't anything to optimize. > > Not to say that there aren't a gazillion other places in the kernel that > could use more eyes and testing. ^Hint hint^ That's something I'd like to help with, hence my (not very good) submissions. You're one of the kernel colonels, so I'm happy to get some *useful* feedback which enables noobs like me to get a better understanding of the kernel stuff. Also, credits to graysky because this is actually based on his work. > > Thx. >