linux-kernel - Re: [PATCH v2 22/32] selftests/ftrace: Add ringbuffer size changing testcase

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Date:   Fri, 31 Aug 2018 08:35:28 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Shuah Khan <shuah@...nel.org>, Ingo Molnar <mingo@...hat.com>,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 22/32] selftests/ftrace: Add ringbuffer size changing
 testcase

On Thu, 30 Aug 2018 11:50:55 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Thu, 30 Aug 2018 16:12:18 +0900
> Masami Hiramatsu <mhiramat@...nel.org> wrote:
> 
> > > I'm fine with this, but one day I need to port over some of my other
> > > tests. I have a test that stresses the ring buffer size (basically
> > > checks to see if it can cause an oom). I need to port that to
> > > selftests. But for now...  
> > 
> > Hmm, such stress test is not good for kselftest, since it can cause
> > oom and kill some test process. Maybe we should have such stresstest
> > framework (which allows test to crash kernel)
> 
> The point of the test is to make sure that it doesn't kill
> everything :-)  The ring buffer code is suppose to detect that it will
> cause an OOM, and if it does that's considered a failure.

Ah, OK, so the test itself must not cause OOM. That's reasonable. :)

> 
> Just like any other test, if it fails, it can crash the kernel. But the
> ring buffer code is suppose to be able to keep the kernel from crashing
> (including triggering OOM) if the buffer size is stressed.
> 
> Maybe I'll port that over today :-/

Looking forward it!

Thank you,

> 
> 
> -- Steve


-- 
Masami Hiramatsu <mhiramat@...nel.org>