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Message-ID: <48E0F7B9.3040301@nortel.com>
Date: Mon, 29 Sep 2008 09:43:53 -0600
From: "Chris Friesen" <cfriesen@...tel.com>
To: Ingo Molnar <mingo@...e.hu>
CC: Peter Zijlstra <a.p.zijlstra@...llo.nl>,
linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>
Subject: Re: unpredictability in scheduler test results -- still present
Ingo Molnar wrote:
> * Chris Friesen <cfriesen@...tel.com> wrote:
>> It turns out that disabling CONFIG_DYNAMIC_FTRACE makes the load
>> balancing problem go away and causes all cpus to be used.
>>
>> With this option enabled, the problem seems to be present as far back
>> as 2.6.27-rc2. (2.6.27-rc1 doesn't compile on my machine, and 2.6.26
>> doesn't have ftrace).
>>
>> I have no idea why turning on dynamic ftrace would affect load
>> balancing behaviour, but it's very repeatable. The very first test
>> run after booting works fine, and all successive runs fail to balance
>> properly.
> OTOH, what does 'truning on dftrace' exactly mean? Just enabling it in
> the .config, or also activating it via /debug/tracing/current_tracer?
Just enabling it in the .config is enough to trigger the behaviour
change. I'm not explicitly activating any traces.
Chris
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