linux-kernel - Re: [PATCH] selftests: ftrace: Use md5sum to take less time of checking logs

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Date:   Wed, 28 Jun 2017 10:17:28 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     linux-kselftest@...r.kernel.org, shuah@...nel.org,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] selftests: ftrace: Use md5sum to take less time of
 checking logs

On Tue, 27 Jun 2017 19:28:32 +0900
Masami Hiramatsu <mhiramat@...nel.org> wrote:

> Use md5sum so that it takes less time of checking
> trace logs update. Since busybox tail/cat takes too
> long time to read the trace log, this uses md5sum
> to check whether trace log is updated or not.

How much faster is md5sum? I can see this causing issues in other
environments.

-- Steve

> 
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> ---
>  .../test.d/ftrace/func_traceonoff_triggers.tc      |    6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/testing/selftests/ftrace/test.d/ftrace/func_traceonoff_triggers.tc b/tools/testing/selftests/ftrace/test.d/ftrace/func_traceonoff_triggers.tc
> index 9cf3852..7a9ab4f 100644
> --- a/tools/testing/selftests/ftrace/test.d/ftrace/func_traceonoff_triggers.tc
> +++ b/tools/testing/selftests/ftrace/test.d/ftrace/func_traceonoff_triggers.tc
> @@ -103,11 +103,11 @@ if [ $on != "0" ]; then
>      fail "Tracing is not off"
>  fi
>  
> -line1=`cat trace | tail -1`
> +csum1=`md5sum trace`
>  sleep $SLEEP_TIME
> -line2=`cat trace | tail -1`
> +csum2=`md5sum trace`
>  
> -if [ "$line1" != "$line2" ]; then
> +if [ "$csum1" != "$csum2" ]; then
>      fail "Tracing file is still changing"
>  fi
>