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Subject: Re: Unable to use tools/perf sched and timechart correctly
From: Peter Zijlstra <peterz@infradead.org>
To: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Cc: =?ISO-8859-1?Q?T=F6r=F6k?= Edwin <edwintorok@gmail.com>,
       Paul Mackerras <paulus@samba.org>, Ingo Molnar <mingo@elte.hu>,
       Linux Kernel <linux-kernel@vger.kernel.org>
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Date: Sun, 06 Dec 2009 11:55:05 +0100
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On Sun, 2009-12-06 at 18:41 +0800, Xiao Guangrong wrote:

> You should enable "CONFIG_SCHED_DEBUG", because we use
> "/proc/<pid>/sched" file to get the task's cpu usage.
> 
> Ingo, I think we do better show the reason about this error,
> just like:
> 
> ---
>  tools/perf/builtin-sched.c |    6 +++++-
>  1 files changed, 5 insertions(+), 1 deletions(-)
> 
> diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
> index 26b782f..f823631 100644
> --- a/tools/perf/builtin-sched.c
> +++ b/tools/perf/builtin-sched.c
> @@ -427,7 +427,11 @@ static u64 get_cpu_usage_nsec_self(void)
>  
>  	sprintf(filename, "/proc/%d/sched", getpid());
>  	file = fopen(filename, "r");
> -	BUG_ON(!file);
> +	if (!file)
> +	{
> +		printf("You should compile your kernel with CONFIG_SCHED_DEBUG option\n");
> +		BUG_ON(1);
> +	}
>  
>  	while ((chars = getline(&line, &len, file)) != -1) {
>  		ret = sscanf(line, "se.sum_exec_runtime : %ld.%06ld\n",

Hrmm, we shouldn't be using a proc file at all, the best solution is to
remove this dependency.



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