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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT autolearn=ham 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 54DF0C43381 for ; Sun, 10 Mar 2019 13:16:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1DA8C207E0 for ; Sun, 10 Mar 2019 13:16:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="ECTXSl11" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726571AbfCJNQf (ORCPT ); Sun, 10 Mar 2019 09:16:35 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:53324 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725939AbfCJNQf (ORCPT ); Sun, 10 Mar 2019 09:16:35 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=9nAbjnqR1YHGPF6LnEc2s+BbzzPNwap/xfIyv2GoGvs=; b=ECTXSl114c4FcWxrtjk42l+V9 eda8J51xg7a1B7tuh33idBkrumaT4EZ4dd3dUxnLiDeZMExWYk4SpUH+HU0ud84A0QVog/htJdqf4 HJJX+QSywzdLIU+MMhYpa7UgieIUw6SZ3ZB6Us54iHGknZ5Rgyi408k3hSklAJmOhF1FORrhJz4o3 9LBqHjhTWsmwuQCoZ/KSToPMGBRsS3gVNvpf96bubAvk/B/kpWdf16n6tKUZU4gT3U9W0N3s6RDCQ 4FuvLm66HTMVD3cPhZstdIPsGsT8A5oL0E/rddPZpYnVuv13x3WF6evyadYPdo7MlzW3ZMNrMax62 rQbA5623A==; Received: from [188.207.104.17] (helo=worktop.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1h2yJS-000878-Nw; Sun, 10 Mar 2019 13:16:22 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id 3B2CC981BBE; Sun, 10 Mar 2019 14:16:20 +0100 (CET) Date: Sun, 10 Mar 2019 14:16:20 +0100 From: Peter Zijlstra To: Steven Rostedt Cc: Linus Torvalds , Josh Poimboeuf , Thomas Gleixner , Peter Anvin , Julien Thierry , Will Deacon , Andy Lutomirski , Ingo Molnar , Catalin Marinas , James Morse , valentin.schneider@arm.com, Brian Gerst , Andrew Lutomirski , Borislav Petkov , Denys Vlasenko , Linux List Kernel Mailing , Dmitry Vyukov , Slavomir Kaslev Subject: Re: [PATCH 00/20] objtool: UACCESS validation v3 Message-ID: <20190310131620.GL2482@worktop.programming.kicks-ass.net> References: <20190307114511.870090179@infradead.org> <20190307120317.GD32477@hirez.programming.kicks-ass.net> <20190307125526.GB32534@hirez.programming.kicks-ass.net> <20190307131312.GC32534@hirez.programming.kicks-ass.net> <20190307164705.qbu4ytdfdmsighas@treble> <20190307171709.dap5hfeof4yo3nsc@treble> <20190307173810.GI32477@hirez.programming.kicks-ass.net> <20190307131841.3b5d9e00@oasis.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190307131841.3b5d9e00@oasis.local.home> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 07, 2019 at 01:18:41PM -0500, Steven Rostedt wrote: > On Thu, 7 Mar 2019 09:45:35 -0800 > Linus Torvalds wrote: > > > On Thu, Mar 7, 2019 at 9:38 AM Peter Zijlstra wrote: > > > > > > Also; it seems to me that something PT, or maybe even simply: > > > > > > perf -e branches -e branch-misses > > > > > > would get you similar or sufficient information. > I currently have one of my engineers looking at the data and may be > sending patches soon. It's basically an entry level way to get into > kernel development. Note, no patch will be sent just because of the > data from the profiling. The task is to look at and understand the > code, and see if it can be optimized (with likely/unlikely or flow > changes). It's a way to get a better understanding of the kernel in > various locations. It is by no means "profiler said this, lets change > it." All changes must be rational, and make sense. The profiler is only > used to help find those places. Can't you just have those same engineers look at perf data? This seems like a very expensive and convoluted way of getting something.