linux-kernel - Re: [PATCH] kselftests: ftrace: limit the executing time by reading from cached trace

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Date:   Mon, 18 Oct 2021 22:16:36 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Li Zhijian <lizhijian@...fujitsu.com>
Cc:     <mingo@...hat.com>, <shuah@...nel.org>,
        <linux-kselftest@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Philip Li <philip.li@...el.com>,
        kernel test robot <lkp@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>
Subject: Re: [PATCH] kselftests: ftrace: limit the executing time by reading
 from cached trace

On Mon, 18 Oct 2021 21:26:16 +0800
Li Zhijian <lizhijian@...fujitsu.com> wrote:

> LKP/0day observed that kselftests/ftrace cannot finish within 1 hour on
> a 96 cpus platform where it hangs in the line like:
> 'cat trace | grep -v ^# | awk '{ print $5 }' | sort -u | wc -l'
> subsystem-enable.tc
> 
> It seems that trace will keep growing during it's read by 'cat' command.
> Consequently, trace becomes too large to finish reading.
> 
> replace 'cat trace' by:
> $ sed -i 's/cat trace |/read_cached_trace |/g' $(find test.d -name "*.tc")
> 

Instead, what happens if you add this command to each test?

if [ -t options/pause-on-trace ]; then
   echo 1 > options/pause-on-trace
fi

We also need to add to the "initialize_ftrace" function in test.d/functions.

if [ -t options/pause-on-trace ]; then
   echo 0 > options/pause-on-trace
fi

-- Steve

> CC: Philip Li <philip.li@...el.com>
> Reported-by: kernel test robot <lkp@...el.com>
> Signed-off-by: Li Zhijian <lizhijian@...fujitsu.com>
> ---