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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_2 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 F2467C433E0 for ; Fri, 12 Mar 2021 17:27:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A8A7264DF2 for ; Fri, 12 Mar 2021 17:27:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231855AbhCLR0m (ORCPT ); Fri, 12 Mar 2021 12:26:42 -0500 Received: from mail.kernel.org ([198.145.29.99]:55378 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231636AbhCLR0Z (ORCPT ); Fri, 12 Mar 2021 12:26:25 -0500 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2B69D64E76; Fri, 12 Mar 2021 17:26:24 +0000 (UTC) Date: Fri, 12 Mar 2021 12:26:22 -0500 From: Steven Rostedt To: Borislav Petkov Cc: Sedat Dilek , Peter Zijlstra , x86@kernel.org, hpa@zytor.com, torvalds@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-toolchains@vger.kernel.org, jpoimboe@redhat.com, alexei.starovoitov@gmail.com, mhiramat@kernel.org Subject: Re: [PATCH 0/2] x86: Remove ideal_nops[] Message-ID: <20210312122622.603bd82c@gandalf.local.home> In-Reply-To: <20210312144726.GA22098@zn.tnic> References: <20210312113253.305040674@infradead.org> <20210312144726.GA22098@zn.tnic> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-toolchains@vger.kernel.org On Fri, 12 Mar 2021 15:47:26 +0100 Borislav Petkov wrote: > On Fri, Mar 12, 2021 at 03:29:48PM +0100, Sedat Dilek wrote: > > What does this change exactly mean to/for me? > > Probably nothing. > > I would be very surprised if it would be at all noticeable for you - > it's not like the kernel is executing long streams of NOPs in fast > paths. > With ftrace enabled, every function starts with a NOP. But that said, the simple answer is for Sedat to apply the patches on his box and do some performance testing. It doesn't matter if you are white, black, male, female, or anything in between. As my daughter's swim coach said; it's the numbers that matter here. Run a bunch of benchmarks on your box on the latest kernel, apply Peter's patches, and then run the benchmarks again on the latest kernel with Peter's patches and then report the difference. If it's negligible then there's nothing to worry about. -- Steve