Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933622AbcLTMfW (ORCPT ); Tue, 20 Dec 2016 07:35:22 -0500 Received: from cassarossa.samfundet.no ([193.35.52.29]:55846 "EHLO cassarossa.samfundet.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751520AbcLTMfT (ORCPT ); Tue, 20 Dec 2016 07:35:19 -0500 X-Greylist: delayed 2120 seconds by postgrey-1.27 at vger.kernel.org; Tue, 20 Dec 2016 07:35:19 EST Date: Tue, 20 Dec 2016 12:59:54 +0100 From: "Steinar H. Gunderson" To: peterz@infradead.org Cc: linux-kernel@vger.kernel.org Subject: Inlined functions in perf report Message-ID: <20161220115954.GA35897@sesse.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit X-Operating-System: Linux 4.9.0 on a x86_64 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 Content-Length: 2137 Lines: 70 Hi Peter, I can't find a good point of contact for perf, so I'm contacting you based on the MAINTAINERS file; feel free to redirect somewhere if you're not the right person. I'm trying to figure out how to deal with perf report when there are inlined functions; they don't generally seem to show up in the call stack, which sometimes can make it very hard to figure out what is going, especially in a code base one doesn't know too well. As an example, I threw together a minimal test program: #include inline int foo() { int k = rand(); int sum = 1; for (int i = 0; i < 10000000000; ++i) { sum ^= k; sum += k; } return sum; } int main(void) { return foo(); } Compiling with -O2 -g, and running perf record -g yields: # Samples: 6K of event 'cycles:ppp' # Event count (approx.): 5876825543 # # Children Self Command Shared Object Symbol # ........ ........ ....... ................. ...................... # 99.98% 99.98% inline inline [.] main | ---0x706258d4c544155 main 99.98% 0.00% inline [unknown] [.] 0x0706258d4c544155 | ---0x706258d4c544155 main Is there a way I can get it to show “foo” in the call graph? (I suppose also ideally, “foo” and not “main” should show up in a non-graph run.) Of course, this gets even more confusing if foo calls bar, since it now looks like the call chain is main -> bar directly. I have debug information that should be sufficient in the binary, because if I break in gdb, I definitely get the call stack: Program received signal SIGINT, Interrupt. 0x0000555555554589 in foo () at inline.c:5 5 int k = rand(); (gdb) bt #0 0x0000555555554589 in foo () at inline.c:5 #1 main () at inline.c:17 (gdb) FWIW, this is with perf from 4.10 (git as of a few days ago) and GCC 6.2.1. /* Steinar */ -- Homepage: https://www.sesse.net/