From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932121AbaEHWh4 (ORCPT ); Thu, 8 May 2014 18:37:56 -0400 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.228]:23142 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755669AbaEHWhz (ORCPT ); Thu, 8 May 2014 18:37:55 -0400 Date: Thu, 8 May 2014 18:37:52 -0400 From: Steven Rostedt To: Thomas Gleixner Cc: LKML , x86@kernel.org, "H. Peter Anvin" , Ingo Molnar , Josh Poimboeuf , Jiri Kosina Subject: Re: [RFC PATCH] ftrace/x86: Move the mcount/fentry code out of entry_64.S Message-ID: <20140508183752.19e99780@gandalf.local.home> In-Reply-To: References: <20140508152152.2130e8cf@gandalf.local.home> X-Mailer: Claws Mail 3.9.3 (GTK+ 2.24.22; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-RR-Connecting-IP: 107.14.168.142:25 X-Cloudmark-Score: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 9 May 2014 00:21:37 +0200 (CEST) Thomas Gleixner wrote: > On Thu, 8 May 2014, Steven Rostedt wrote: > > I'm fine with the code move per se. That's a good thing. Great, then I'll add this to my 3.16 queue. Can I get your Acked-by for it? > > The live patcher argumentation for it is more than questionable. Well, that was the final motivator. But I've been wanting to optimize the function tracing a bit since it's been getting more and more users. Namely, kprobes and perf. As such, I've been thinking about creating custom trampolines (like what kprobes does today) where if there's two or more users of ftrace, but they are using different functions, they don't need to go through a loop, but instead have their own trampoline that calls their function directly and is called by the functions they trace. Right now I'm working on getting the function graph tracer trampoline (which is static) called directly if function graph is enabled. Currently, we save regs for function tracing, restore them, and then call function graph tracing. This is a big waste when function graph is running by itself. -- Steve