Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754925Ab2K2XAs (ORCPT ); Thu, 29 Nov 2012 18:00:48 -0500 Received: from mail-pa0-f46.google.com ([209.85.220.46]:57875 "EHLO mail-pa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753217Ab2K2XAr (ORCPT ); Thu, 29 Nov 2012 18:00:47 -0500 Message-ID: <50B7E91C.6070403@gmail.com> Date: Thu, 29 Nov 2012 15:00:44 -0800 From: David Daney User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/17.0 Thunderbird/17.0 MIME-Version: 1.0 To: Alan Cooper CC: ralf@linux-mips.org, linux-mips@linux-mips.org, linux-kernel@vger.kernel.org Subject: Re: MIPS Function Tracer question References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2826 Lines: 72 On 11/29/2012 01:04 PM, Alan Cooper wrote: > I've been doing some testing of the MIPS Function Tracer functionality > on the 3.3 kernel. I was surprised to find that the option to generate > frame pointers was required for tracing. It is not really required for MIPS function tracing, but the Kconfigs for some reason set it. > When I don't enable > FRAME_POINTER along with FUNCTION_TRACER, the kernel hangs on boot. I > also noticed that a checkin to the 3.4 kernel > (b732d439cb43336cd6d7e804ecb2c81193ef63b0) no longer forces on > FRAME_POINTER when FUNCTION_TRACER is selected. I was wondering how it > works in 3.4 and beyond, so I built a Malta kernel from the latest > MIPS tree with FUNCTION_TRACING enabled and tested it with QEMU. The > kernel hung the same way. I can think of 2 reasons for this: > 1. Function tracing is broken for MIPS in 3.4 and beyond. > 2. The 4.5.3 GNU C compiler I'm using is generating different code for > function tracing. Function tracing works best with recent versions of GCC (those that support -mmcount-ra-address). > I was wondering if anyone has MIPS function tracing working in 3.4 or later? Yes. Using GCC 4.7.0 on an octeon kernel (based on 3.4.14): # tracer: function_graph # # CPU DURATION FUNCTION CALLS # | | | | | | | 1) | __fsnotify_parent() { 1) 7.154 us | } /* __fsnotify_parent */ 1) | fsnotify() { 1) | __srcu_read_lock() { 1) | add_preempt_count() { 1) 1.356 us | } /* add_preempt_count */ 1) | sub_preempt_count() { 1) 1.385 us | } /* sub_preempt_count */ 1) 6.747 us | } /* __srcu_read_lock */ 1) | __srcu_read_unlock() { 1) | add_preempt_count() { 1) 1.383 us | } /* add_preempt_count */ 1) | sub_preempt_count() { 1) 1.358 us | } /* sub_preempt_count */ 1) 6.642 us | } /* __srcu_read_unlock */ 1) + 17.861 us | } /* fsnotify */ . . . > > I did figure out why it's hanging and I have some changes that will > allow the function tracer to run without frame pointers, but before I > proceed I want to rule out compiler differences. > > Thanks > -- > 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/ > > -- 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/