Subject: Re: [linux-audio-dev] oprofile, redhat and CONFIG_PREEMPT
From: Paul Davis (paul_AT_linuxaudiosystems.com)
Date: Wed Jan 21 2004 - 22:54:56 EET
>The FAQ recommends downloading a redhat's oprofile rpm, which we did.
>But that is configured not to work with a CONFIG_PREEMPT kernel. Our
>kernel is CONFIG_PREEMPT patched for increased audio performance.
>
>Yikes!
>
>Has anyone run in to this problem and found a clever solution? An
>alternate profiler that works? Will we get meaningful results if we
>rebuild the kernel with CONFIG_PREEMPT turned off? Or perhaps we can run
>it with CONFIG_PREEMPT on and see what happens?
preemption is not particularly helpful for low latency audio in the
first place. in measurements done by someone at IBM (IIRC), the low
latency patches provide the biggest chunk of improvement, with the
preemption stuff providing just a small extra bit on top.
the preemption patch will change your results a bit (if you could get
them), but i don't think it would be a qualitative change.
and personally, i prefer andrew morton's timepeg code although that is
more for use tuning specific parts of the kernel rather than overall
profiling.
--p
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