Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762682Ab2FVSH0 (ORCPT ); Fri, 22 Jun 2012 14:07:26 -0400 Received: from mail-wg0-f42.google.com ([74.125.82.42]:50275 "EHLO mail-wg0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752345Ab2FVSHW convert rfc822-to-8bit (ORCPT ); Fri, 22 Jun 2012 14:07:22 -0400 MIME-Version: 1.0 In-Reply-To: <20120622133650.GA24136@gmail.com> References: <20120622133650.GA24136@gmail.com> From: Linus Torvalds Date: Fri, 22 Jun 2012 11:07:01 -0700 X-Google-Sender-Auth: GdzmkJKr2E3NKeGWbz27Eyudl7A Message-ID: Subject: Re: [GIT PULL] perf fixes To: Ingo Molnar , Steven Rostedt Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , Arnaldo Carvalho de Melo , Thomas Gleixner , Andrew Morton Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1459 Lines: 35 On Fri, Jun 22, 2012 at 6:36 AM, Ingo Molnar wrote: > > Steven Rostedt (1): > ? ? ?ftrace: Make all inline tags also include notrace Btw, this is something I've been wondering about: function call tracing and inlining seems to be fundamentally incompatible. And gcc can (and does, depending on version and details) inline pretty much any static function, whether we mark it inline or not. Now, there's no question that we don't want inlined functions to be traced, but that actually means that the *logical* thing would be to try to somehow tell gcc to not ever do the whole stupid mcount thing for functions that *might* be inlined - and at least be consistent about it. IOW, is there some way to get the mcount thing to only happen for functions that either have their address taken, or have external visibility? Because that mcount thing is expensive as hell, if people haven't noticed (and I'm not talking about just the call instruction that I think we can stub out - it changes code generation in other ways too). And it looks like distros enable it by default, which annoys my performance-optimizing soul deeply. So doing it a bit less would be lovely. Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/