Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932773AbdCUOon (ORCPT ); Tue, 21 Mar 2017 10:44:43 -0400 Received: from mail-pf0-f194.google.com ([209.85.192.194]:36509 "EHLO mail-pf0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757076AbdCUOol (ORCPT ); Tue, 21 Mar 2017 10:44:41 -0400 Subject: Re: [PATCH 2/4] perf annotate: Avoid division by zero when calculating percent To: Arnaldo Carvalho de Melo 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> <20170321142155.GC3641@kernel.org> Cc: linux-kernel@vger.kernel.org, Jiri Olsa , Namhyung Kim , Ingo Molnar , Peter Zijlstra , Wang Nan , Masami Hiramatsu , Jiri Olsa From: Taeung Song Message-ID: <2c99da8d-37f8-5c31-7c9c-b3e02d8516b5@gmail.com> Date: Tue, 21 Mar 2017 23:36:24 +0900 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: <20170321142155.GC3641@kernel.org> Content-Type: text/plain; charset=windows-1252; 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: 5877 Lines: 110 Hi, On 03/21/2017 11:21 PM, Arnaldo Carvalho de Melo wrote: > 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. > Okey, I found the cause about -nan and sent this patch to you. But do you want to get other way to fix this problem ? instead of this patch ? Or change the commit message ? Thanks, Taeung