From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753387AbcKUSG5 (ORCPT ); Mon, 21 Nov 2016 13:06:57 -0500 Received: from one.firstfloor.org ([193.170.194.197]:51630 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752264AbcKUSG4 (ORCPT ); Mon, 21 Nov 2016 13:06:56 -0500 Date: Mon, 21 Nov 2016 10:06:54 -0800 From: Andi Kleen To: Steven Rostedt Cc: Andi Kleen , Peter Zijlstra , Jiri Olsa , "Paul E. McKenney" , linux-kernel@vger.kernel.org, Ingo Molnar , Josh Triplett , Jan Stancek Subject: Re: [BUG] msr-trace.h:42 suspicious rcu_dereference_check() usage! Message-ID: <20161121180654.GV26852@two.firstfloor.org> References: <20161121005343.GB1891@krava> <20161121092850.GF3102@twins.programming.kicks-ass.net> <20161121170612.GT26852@two.firstfloor.org> <20161121171853.GK3092@twins.programming.kicks-ass.net> <20161121174504.GU26852@two.firstfloor.org> <20161121130115.2f0f38e7@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161121130115.2f0f38e7@gandalf.local.home> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > And a popf can be much more expensive than any of these. You should > know, not all instructions are equal. > > Using perf, I've seen popf take up almst 30% of a function the size of > this. In any case it's a small fraction of the 600+ instructions which are currently executed for every enabled trace point. If ftrace was actually optimized code this would make some sense, but it clearly isn't ... -Andi