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Date: Wed, 09 Dec 2009 22:47:20 -0500 From: Steven Rostedt <rostedt@...dmis.org> To: Tim Bird <tim.bird@...sony.com> Cc: linux kernel <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>, Frederic Weisbecker <fweisbec@...il.com> Subject: Re: [PATCH 4/4] ftrace - function_duration Documentation On Wed, 2009-12-09 at 14:42 -0800, Tim Bird wrote: > Documentation for function_duration tracer. > +The purpose of the function duration tracer is to help find the > +longest-running, most time-consuming functions in the Linux kernel. > +This is especially important for early initialization, to reduce > +kernel boot time. > + > +Function duration tracing uses the ftrace ability to hook both the > +entry and exit of a function, to record duration information for > +kernel functions. This is similar to the function_graph tracer, but > +the function_duration tracer is specially written to support filtering > +by duration and decreased tracer overhead while filtering. > + > +This extends the amount of time that a trace can cover, and reduces > +interference with the timing of the traced activity. BTW, have you taken a look at the function profiler? It also keeps track of all durations without using the ring buffer. It just adds them up and gives an average time. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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