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Date: Wed, 1 Feb 2017 16:27:02 +0900 From: Taeung Song <treeze.taeung@...il.com> To: Arnaldo Carvalho de Melo <arnaldo.melo@...il.com> Cc: linux-kernel@...r.kernel.org, Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>, Ingo Molnar <mingo@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Wang Nan <wangnan0@...wei.com> Subject: Re: [PATCH v2 2/4] perf ftrace: Add ftrace.tracer config option On 01/31/2017 10:15 PM, Arnaldo Carvalho de Melo wrote: > Em Tue, Jan 31, 2017 at 09:46:28AM -0300, Arnaldo Carvalho de Melo escreveu: >> Also you are silently ignoring any unknown variable in this section, so >> if someone has this: >> >> cat ~/.perfconfig >> >> [ftrace] >> >> trace = function >> >> >> I.e. forgets the 'r', it will keep using the current default, >> "function_graph" till the user checks the config and adds that missing >> 'r'... >> >> I haven't changed this because I think this is so common that we should >> instead have a different error return for those config callbacks that >> will tell perf_config() to say something like: >> >> "unknown variable %s.%s\n", section_name, variable_name > > So I read a bit more the config code and ended up with this: > > static int perf_ftrace_config(const char *var, const char *value, void *cb) > { > struct perf_ftrace *ftrace = cb; > > if (prefixcmp(var, "ftrace.")) > return 0; > > if (strcmp(var, "ftrace.tracer")) > return -1; > > if (!strcmp(value, "function_graph") || > !strcmp(value, "function")) { > ftrace->tracer = value; > return 0; > } > > pr_err("Please select \"function_graph\" (default) or \"function\"\n"); > return -1; > } > > I.e. it will ignore variables for other sections and will stop at an unknown > variable or value for ftrace.tracer: > > [root@...et ~]# cat ~/.perfconfig > [ftrace] > trace = function > [root@...et ~]# perf ftrace usleep 1 > Error: wrong config key-value pair ftrace.trace=function > [root@...et ~]# cat ~/.perfconfig > [ftrace] > tracer = functin > [root@...et ~]# perf ftrace usleep 1 > Please select "function_graph" (default) or "function" > Error: wrong config key-value pair ftrace.tracer=functin > [root@...et ~]# cat ~/.perfconfig > [ftrace] > tracer = function > [root@...et ~]# perf ftrace usleep 1 | head -5 > <idle>-0 [000] d... 3855.820847: switch_mm_irqs_off <-__schedule > <...>-18550 [000] d... 3855.820849: finish_task_switch <-__schedule > <...>-18550 [000] d... 3855.820851: smp_irq_work_interrupt <-irq_work_interrupt > <...>-18550 [000] d... 3855.820851: irq_enter <-smp_irq_work_interrupt > <...>-18550 [000] d... 3855.820851: rcu_irq_enter <-irq_enter > [root@...et ~]# > This is great!! I agonized about error message for each other cases as above! But I think this is more precise than my patch! Thanks, Taeung
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