Received: by 2002:a05:6a10:9848:0:0:0:0 with SMTP id x8csp1438093pxf; Fri, 12 Mar 2021 09:28:16 -0800 (PST) X-Google-Smtp-Source: ABdhPJz9DdtKnYuvxo+DURg82czhDo5iX2IGXudqlNUrxJQLDeDQGHefw6fZEdZWR4VU15CJPKqw X-Received: by 2002:a17:906:f12:: with SMTP id z18mr9773610eji.132.1615570096501; Fri, 12 Mar 2021 09:28:16 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1615570096; cv=none; d=google.com; s=arc-20160816; b=Z8sP5q3ASELl3NV1mFQyzLoC7SOktuI1+1ShcPipuXPl0MiG8RLDrPmcazPGdxODHX HwNj7gl40fpWU4AtEram40Xs2gVnBCtrDKA3S3Feuszw5q7BGf0ngyXe9nW+Xvd1vSF5 RQKCuGIbOus3Lsvylyp4dZ1F+sqngeJ1LQwIaaztCs+XpHH0PWsA/MMPL+K6suloQXey tQWnw7TBNq6mc70RbNB90SbgBUmjD9UGfJ6CeiZGoNRPwNVcXs46DyR6IOfqHXTPU5Ee MhKx6jN+zshV20x/PKSXL4ccqo9p/B5DMw+XD1evUpwCU+fWCk1CD2B5Ex2hsRnlq4UJ 3T8A== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:subject:cc:to:from:date; bh=SE3xgGTtC6Ly2hohmVh+7qUUL1IdUogIAhuA4c8M4RE=; b=S/1RK4Eefgsw33kD/TCaaNslffDulACABox0Siz199UvS2NOwRn/HdkR5nDFSRAE5w +PknqTVI6WatMmGqu6u0CjJZS2sH8Q8mizfQ+eEOz4O2NXZdRyWsUlIloOxb7dyEwu6P Gq9KhHVEsa2dTqq+yw/ah7SKYvVphRKulJKC4hGiXVG8NyEg1IUv2/v+FFB7ZpKyxpau lb2VDTNXatVTeI7wX2/2+4DUBWwhFddfBpKWZi2cGW/mMJe9NCDwnTFWzmEH5iY9n564 kJlDfh2EdjR4v48bQHxglHJyJ9jtGUQ/GosJr7LaXoYopyNAk8+svOH+N2/hSqCQawx6 2BRw== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id hd34si4654117ejc.197.2021.03.12.09.27.51; Fri, 12 Mar 2021 09:28:16 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232043AbhCLR0m (ORCPT + 99 others); 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-kernel@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