Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932927AbdCUObd (ORCPT ); Tue, 21 Mar 2017 10:31:33 -0400 Received: from mail.kernel.org ([198.145.29.136]:36038 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932885AbdCUObc (ORCPT ); Tue, 21 Mar 2017 10:31:32 -0400 Date: Tue, 21 Mar 2017 11:21:55 -0300 From: Arnaldo Carvalho de Melo To: Taeung Song Cc: Arnaldo Carvalho de Melo , linux-kernel@vger.kernel.org, Jiri Olsa , Namhyung Kim , Ingo Molnar , Peter Zijlstra , Wang Nan , Masami Hiramatsu , Jiri Olsa Subject: Re: [PATCH 2/4] perf annotate: Avoid division by zero when calculating percent Message-ID: <20170321142155.GC3641@kernel.org> References: <1489978617-31396-1-git-send-email-treeze.taeung@gmail.com> <1489978617-31396-3-git-send-email-treeze.taeung@gmail.com> <20170320181559.GD27647@kernel.org> <939347e4-593c-4ef6-37d9-daa2fee3aed8@gmail.com> <20170321141407.GB3641@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170321141407.GB3641@kernel.org> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.8.0 (2017-02-23) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5492 Lines: 98 Em Tue, Mar 21, 2017 at 11:14:07AM -0300, Arnaldo Carvalho de Melo escreveu: > Em Tue, Mar 21, 2017 at 07:20:20AM +0900, Taeung Song escreveu: > > And, > > I tested by perf-stat on the same situation as below. > > > > $ perf stat -e "{cycles,page-faults,branch-misses}" ./old > 6623856 > > Please always try to spell out all the steps needed to get to some > result, for instance, in this case the info above, that you are asking > for three counters to be recorded at once probably has the key to > reproduce this, as I think that you may run your workload and sometimes > not get one page fault, leading tho that division by zero, but I have to > try to reproduce it now that I have this clue. Bingo! [root@jouet ~]# perf record -e "{cycles,page-faults,branch-misses}" usleep 1 [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.020 MB perf.data (20 samples) ] [root@jouet ~]# perf annotate -l --stdio 2>&1 | grep -w nan | head 100.00 -nan 100.00 msr.h:104 0.00 -nan 0.00 : ffffffff81060bf0: mov %edi,%ecx 0.00 -nan 0.00 : ffffffff81060bf2: mov %esi,%eax 0.00 -nan 0.00 : ffffffff81060bf4: wrmsr msr.h:104 100.00 -nan 100.00 : ffffffff81060bf6: nopl 0x0(%rax,%rax,1) 0.00 -nan 0.00 : ffffffff81060bfb: retq 0.00 -nan 0.00 : ffffffff81060bfc: push %rbp 0.00 -nan 0.00 : ffffffff81060bfd: mov %esi,%eax 0.00 -nan 0.00 : ffffffff81060bff: mov %rdx,%rsi 0.00 -nan 0.00 : ffffffff81060c02: shl $0x20,%rsi [root@jouet ~]# So, if we don't use -l/--print-line we get: [root@jouet ~]# perf annotate --stdio --no-source native_write_msr Percent | Source code & Disassembly of vmlinux for cycles (3 samples) ------------------------------------------------------------------------------------------- : ffffffff81060bf0 : : __wrmsr(): 0.00 0.00 0.00 : ffffffff81060bf0: mov %edi,%ecx 0.00 0.00 0.00 : ffffffff81060bf2: mov %esi,%eax 0.00 0.00 0.00 : ffffffff81060bf4: wrmsr : arch_static_branch(): 100.00 0.00 100.00 : ffffffff81060bf6: nopl 0x0(%rax,%rax,1) : native_write_msr(): 0.00 0.00 0.00 : ffffffff81060bfb: retq 0.00 0.00 0.00 : ffffffff81060bfc: push %rbp 0.00 0.00 0.00 : ffffffff81060bfd: mov %esi,%eax 0.00 0.00 0.00 : ffffffff81060bff: mov %rdx,%rsi 0.00 0.00 0.00 : ffffffff81060c02: shl $0x20,%rsi 0.00 0.00 0.00 : ffffffff81060c06: mov %eax,%edx 0.00 0.00 0.00 : ffffffff81060c08: mov %rsp,%rbp 0.00 0.00 0.00 : ffffffff81060c0b: or %rdx,%rsi 0.00 0.00 0.00 : ffffffff81060c0e: xor %edx,%edx 0.00 0.00 0.00 : ffffffff81060c10: callq ffffffff81457df0 0.00 0.00 0.00 : ffffffff81060c15: pop %rbp 0.00 0.00 0.00 : ffffffff81060c16: retq [root@jouet ~]# I.e. one column per event in that group, and no -nan, all is well. But if we ask for --lines it gets b0rked: [root@jouet ~]# perf annotate --stdio --no-source native_write_msr --print-line Sorted summary for file /lib/modules/4.11.0-rc2+/build/vmlinux ---------------------------------------------- 100.00 -nan 100.00 msr.h:104 Percent | Source code & Disassembly of vmlinux for cycles (3 samples) ------------------------------------------------------------------------------------------- : ffffffff81060bf0 : : __wrmsr(): 0.00 -nan 0.00 : ffffffff81060bf0: mov %edi,%ecx 0.00 -nan 0.00 : ffffffff81060bf2: mov %esi,%eax 0.00 -nan 0.00 : ffffffff81060bf4: wrmsr : arch_static_branch(): msr.h:104 100.00 -nan 100.00 : ffffffff81060bf6: nopl 0x0(%rax,%rax,1) : native_write_msr(): 0.00 -nan 0.00 : ffffffff81060bfb: retq 0.00 -nan 0.00 : ffffffff81060bfc: push %rbp 0.00 -nan 0.00 : ffffffff81060bfd: mov %esi,%eax 0.00 -nan 0.00 : ffffffff81060bff: mov %rdx,%rsi 0.00 -nan 0.00 : ffffffff81060c02: shl $0x20,%rsi 0.00 -nan 0.00 : ffffffff81060c06: mov %eax,%edx 0.00 -nan 0.00 : ffffffff81060c08: mov %rsp,%rbp 0.00 -nan 0.00 : ffffffff81060c0b: or %rdx,%rsi 0.00 -nan 0.00 : ffffffff81060c0e: xor %edx,%edx 0.00 -nan 0.00 : ffffffff81060c10: callq ffffffff81457df0 0.00 -nan 0.00 : ffffffff81060c15: pop %rbp 0.00 -nan 0.00 : ffffffff81060c16: retq [root@jouet ~]# I don't have that much time to continue pursuing this, try to continue investigating, I'll try to help and to fix this later. - Arnaldo