From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757025AbbA3OVg (ORCPT ); Fri, 30 Jan 2015 09:21:36 -0500 Received: from mail.kernel.org ([198.145.29.136]:47642 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751299AbbA3OVe (ORCPT ); Fri, 30 Jan 2015 09:21:34 -0500 Date: Fri, 30 Jan 2015 11:21:35 -0300 From: Arnaldo Carvalho de Melo To: Masami Hiramatsu Cc: Peter Zijlstra , namhyung@kernel.org, Ingo Molnar , Linux Kernel Mailing List Subject: Re: [PATCH perf/core 1/2] [BUGFIX] perf-probe: Fix to handle optimized not-inlined but has no instance Message-ID: <20150130142135.GA3101@kernel.org> References: <20150130093741.30575.41526.stgit@localhost.localdomain> <20150130093744.30575.43290.stgit@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150130093744.30575.43290.stgit@localhost.localdomain> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Em Fri, Jan 30, 2015 at 06:37:44PM +0900, Masami Hiramatsu escreveu: > Fix to handle optimized no-inline functions which have > only function definition but no actual instance at > that point. To fix this problem, we need to find actual > instance of the function. > > Without this patch: > ---- > # perf probe -a __up > Failed to get entry address of __up. > Error: Failed to add events. > # perf probe -L __up > Specified source line is not found. > Error: Failed to show lines. > ---- > > With this patch: > ---- > # perf probe -a __up > Added new event: > probe:__up (on __up) > > You can now use it in all perf tools, such as: > > perf record -e probe:__up -aR sleep 1 > > # perf probe -L __up > <__up@/home/fedora/ksrc/linux-3/kernel/locking/semaphore.c:0> > 0 static noinline void __sched __up(struct semaphore *sem) > { > struct semaphore_waiter *waiter = list_first_entry(&sem->wait_ > struct semaphore_waite > 4 list_del(&waiter->list); > 5 waiter->up = true; > 6 wake_up_process(waiter->task); > 7 } > ---- Since __up here was built in some other way, I looked for another 'noinline' function to try, and it failed here: [root@zoo ~]# perf probe -L vmalloc_fault | head -5 0 static noinline int vmalloc_fault(unsigned long address) 1 { pgd_t *pgd, *pgd_ref; pud_t *pud, *pud_ref; [root@zoo ~]# perf probe vmalloc_fault Added new event: Failed to write event: Invalid argument Error: Failed to add events. ---->>>>>> APPLY THE PATCH, rebuild and try again: [root@zoo ~]# perf probe vmalloc_fault Added new event: Failed to write event: Invalid argument Error: Failed to add events. [root@zoo ~]# perf probe -v vmalloc_fault probe-definition(0): vmalloc_fault symbol:vmalloc_fault file:(null) line:0 offset:0 return:0 lazy:(null) 0 arguments Looking at the vmlinux_path (7 entries long) Using /lib/modules/3.19.0-rc6+/build/vmlinux for symbols Open Debuginfo file: /lib/modules/3.19.0-rc6+/build/vmlinux Try to find probe point from debuginfo. Probe point found: vmalloc_fault+0 Found 1 probe_trace_events. Opening /sys/kernel/debug/tracing/kprobe_events write=1 Added new event: Writing event: p:probe/vmalloc_fault _text+289600 Failed to write event: Invalid argument Error: Failed to add events. Reason: Invalid argument (Code: -22) [root@zoo ~]# grep -w vmalloc_fault /proc/kallsyms ffffffff81046b40 t vmalloc_fault [root@zoo ~]# grep -w _text /proc/kallsyms ffffffff81000000 T _text [root@zoo ~]# python Python 2.7.5 (default, Nov 3 2014, 14:26:24) [GCC 4.8.3 20140911 (Red Hat 4.8.3-7)] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> 0xffffffff81046b40 - 0xffffffff81000000 289600L >>> [root@zoo ~]# readelf -s /lib/modules/3.19.0-rc6+/build/vmlinux | egrep -w _text\|vmalloc_fault 3499: ffffffff81046b40 410 FUNC LOCAL DEFAULT 1 vmalloc_fault 48873: ffffffff81000000 0 NOTYPE GLOBAL DEFAULT 1 _text [root@zoo ~]# --------------------------------------------------------------------------- So perhaps I need a 'noinline' _and_ '__sched', so that I have a "optimized no-inline functions which have only function definition but no actual instance at that point"? Looking for one, will post here after objdump -dS finishes... - Arnaldo