Messages in this thread | | | Date | Thu, 10 Dec 2009 13:21:52 -0800 | From | Tim Bird <> | Subject | Re: [PATCH 4/4] ftrace - function_duration Documentation |
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Steven Rostedt wrote: > 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.
I haven't, but I should. However, my tool has some other options (like subtracting time spent in interrupts) that I don't think the profile approach currently supports. -- Tim
============================= Tim Bird Architecture Group Chair, CE Linux Forum Senior Staff Engineer, Sony Corporation of America =============================
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