From mboxrd@z Thu Jan 1 00:00:00 1970 From: Masami Hiramatsu Subject: Re: perf probe + uprobes missing events Date: Tue, 7 Apr 2020 21:39:43 +0900 Message-ID: <20200407213943.3a92e040d4ce30dc55e9aa1f@kernel.org> References: <20200406145356.GA32649@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20200406145356.GA32649@kernel.org> Sender: linux-kernel-owner@vger.kernel.org To: Arnaldo Carvalho de Melo Cc: Jiri Olsa , Kajol Jain , Andi Kleen , Linux Kernel Mailing List , linux-perf-users@vger.kernel.org List-Id: linux-perf-users.vger.kernel.org Hi Arnaldo, On Mon, 6 Apr 2020 11:53:56 -0300 Arnaldo Carvalho de Melo wrote: > Hi Masami, > > I'm trying to use 'perf probe' to debug 'perf test', but I'm not > getting repeatable results, take a look: > > I'm trying to figure out which expresssions are _really_ being tested > byu the 'perf test expr' testcase, so I added a probe to the > expr__parse() routine, asking for the expr string to be printed: > > [root@five ~]# perf probe -x ~/bin/perf -L expr__parse > > 0 int expr__parse(double *final_val, struct expr_parse_ctx *ctx, const char *expr, int runtime) > 1 { > 2 return __expr__parse(final_val, ctx, expr, EXPR_PARSE, runtime) ? -1 : 0; > 3 } > > static bool > already_seen(const char *val, const char *one, const char **other, > > [root@five ~]# > > [root@five ~]# perf probe -x ~/bin/perf expr__parse expr:string > Target program is compiled without optimization. Skipping prologue. > Probe on address 0x5cb11b to force probing at the function entry. > > Added new event: > probe_perf:expr__parse (on expr__parse in /home/acme/bin/perf with expr:string) > > You can now use it in all perf tools, such as: > > perf record -e probe_perf:expr__parse -aR sleep 1 > > [root@five ~]# Hmm, These operation looks good to me. However, > > [root@five ~]# perf trace -e probe_perf:expr_* perf test -F expr > 7: Simple expression parser : Ok > 0.000 :2994175/2994175 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "1+1") > 0.015 :2994175/2994175 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "FOO+BAR") > 0.018 :2994175/2994175 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "(BAR/2)%2") > 0.020 :2994175/2994175 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "1 - -4") > 0.023 :2994175/2994175 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "(FOO-1)*2 + (BAR/2)%2 - -4") > 0.026 :2994175/2994175 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "1-1 | 1") > 0.029 :2994175/2994175 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "1-1 & 1") > 0.031 :2994175/2994175 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "min(1,2) + 1") > 0.034 :2994175/2994175 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "max(1,2) + 1") > 0.036 :2994175/2994175 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "1+1 if 3*4 else 0") > 0.039 :2994175/2994175 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "FOO/0") > 0.041 :2994175/2994175 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "BAR/") > [root@five ~]# perf trace -e probe_perf:expr_* perf test -F expr > 7: Simple expression parser : Ok > 0.000 perf/2996042 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "1+1") > 0.021 perf/2996042 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "FOO+BAR") > 0.025 perf/2996042 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "(BAR/2)%2") > 0.029 perf/2996042 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "1 - -4") > 0.033 perf/2996042 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "(FOO-1)*2 + (BAR/2)%2 - -4") > 0.041 perf/2996042 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "1-1 | 1") > 0.044 perf/2996042 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "1-1 & 1") > [root@five ~]# perf trace -e probe_perf:expr_* perf test -F expr > 7: Simple expression parser : Ok > 0.000 perf/2996416 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "1+1") > 0.020 perf/2996416 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "FOO+BAR") > 0.025 perf/2996416 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "(BAR/2)%2") > 0.029 perf/2996416 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "1 - -4") > 0.032 perf/2996416 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "(FOO-1)*2 + (BAR/2)%2 - -4") > 0.037 perf/2996416 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "1-1 | 1") > 0.040 perf/2996416 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "1-1 & 1") > 0.043 perf/2996416 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "min(1,2) + 1") > 0.046 perf/2996416 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "max(1,2) + 1") > 0.049 perf/2996416 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "1+1 if 3*4 else 0") > 0.053 perf/2996416 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "FOO/0") > 0.056 perf/2996416 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "BAR/") > [root@five ~]# perf trace -e probe_perf:expr_* perf test -F expr > 7: Simple expression parser : Ok > [root@five ~]# perf trace -e probe_perf:expr_* perf test -F expr > 7: Simple expression parser : Ok > [root@five ~]# perf trace -e probe_perf:expr_* perf test -F expr > 7: Simple expression parser : Ok > [root@five ~]# perf trace -e probe_perf:expr_* perf test -F expr > 7: Simple expression parser : Ok > [root@five ~]# perf trace -e probe_perf:expr_* perf test -F expr > 7: Simple expression parser : Ok > 0.000 :2998175/2998175 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "1+1") > 0.014 :2998175/2998175 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "FOO+BAR") > 0.017 :2998175/2998175 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "(BAR/2)%2") > 0.021 :2998175/2998175 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "1 - -4") > 0.024 :2998175/2998175 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "(FOO-1)*2 + (BAR/2)%2 - -4") > 0.030 :2998175/2998175 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "1-1 | 1") > 0.032 :2998175/2998175 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "1-1 & 1") > 0.035 :2998175/2998175 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "min(1,2) + 1") > 0.038 :2998175/2998175 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "max(1,2) + 1") > 0.040 :2998175/2998175 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "1+1 if 3*4 else 0") > 0.044 :2998175/2998175 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "FOO/0") > 0.046 :2998175/2998175 probe_perf:expr__parse(__probe_ip: 6074674, expr_string: "BAR/") > [root@five ~]# Strange. This seems bug in uprobes. Did you try to enable ftrace event and dump ftrace trace buffer for each time? Also, it may help if you dump the /sys/kernel/debug/tracing/uprobe_profile. It may indicate how many times the probe is hit and missed. OK, I'll also try to reproduce it. Thank you, > > > Do you have any idea why that happens? > > - Arnaldo -- Masami Hiramatsu