Messages in this thread | | | Date | Wed, 4 Dec 2013 20:01:04 -0800 | From | Greg Kroah-Hartman <> | Subject | Re: [PATCH 0/3] ARM Coresight: Enhance ETM tracing control |
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On Wed, Dec 04, 2013 at 10:49:25PM -0500, Adrien Vergé wrote: > 2013/12/4 Greg Kroah-Hartman <gregkh@linuxfoundation.org>: > > How much overhead does the existing tracing code have on ARM? Is ETM > > still even needed? Why not just use ETM for the core tracing code > > instead? > > Coresight ETM is not just faster than /sys/kernel/debug/tracing, it > provides more detailed and customisable info. For instance, you can > trace every load, store, instruction fetch, along with the number of > cycles taken, with almost zero-overhead.
Can't you already do that with the 'perf' tool the kernel provides without the ETM driver?
> > What's wrong with the in-kernel tracing logic that you can't use that > > instead of the ETM stuff? > > ETM has a different purpose. Integrating it in > /sys/kernel/debug/tracing would not take advantage of all its > features.
What is it's purpose then? At first glance, this seems to be exactly what 'perf' provides already. Doesn't perf work on ARM today?
thanks,
greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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