linux-kernel - Re: [PATCH 1/1] perf,stat: reduce interval-print to 10ms

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Message-ID: <20151002165624.GC1673@krava.brq.redhat.com>
Date:	Fri, 2 Oct 2015 18:56:24 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	kan.liang@...el.com
Cc:	acme@...nel.org, jolsa@...nel.org, namhyung@...nel.org,
	ak@...ux.intel.com, linux-kernel@...r.kernel.org,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 1/1] perf,stat: reduce interval-print to 10ms

On Fri, Oct 02, 2015 at 05:04:34AM -0400, kan.liang@...el.com wrote:
> From: Kan Liang <kan.liang@...el.com>
> 

SNIP

> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> index a96fb5c..5ef88f7 100644
> --- a/tools/perf/builtin-stat.c
> +++ b/tools/perf/builtin-stat.c
> @@ -1179,7 +1179,7 @@ int cmd_stat(int argc, const char **argv, const char *prefix __maybe_unused)
>  	OPT_STRING(0, "post", &post_cmd, "command",
>  			"command to run after to the measured command"),
>  	OPT_UINTEGER('I', "interval-print", &stat_config.interval,
> -		    "print counts at regular interval in ms (>= 100)"),
> +		    "print counts at regular interval in ms (>= 10)"),
>  	OPT_SET_UINT(0, "per-socket", &stat_config.aggr_mode,
>  		     "aggregate counts per processor socket", AGGR_SOCKET),
>  	OPT_SET_UINT(0, "per-core", &stat_config.aggr_mode,
> @@ -1332,9 +1332,14 @@ int cmd_stat(int argc, const char **argv, const char *prefix __maybe_unused)
>  		thread_map__read_comms(evsel_list->threads);
>  
>  	if (interval && interval < 100) {
> -		pr_err("print interval must be >= 100ms\n");
> -		parse_options_usage(stat_usage, options, "I", 1);
> -		goto out;
> +		if (interval < 10) {
> +			pr_err("print interval must be >= 10ms\n");
> +			parse_options_usage(stat_usage, options, "I", 1);
> +			goto out;
> +		} else
> +			pr_warning("print interval < 100ms. "
> +				   "The overhead percentage could be high in some cases. "
> +				   "Please proceed with caution.\n");

with '-I' 10 this warning flies away quite fast ;-)

I guess it's better than nothing, and I'm not sure
about putting some sleep after that warning..

Acked-by: Jiri Olsa <jolsa@...nel.org>

thanks,
jirka
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