Messages in this thread | | | Date | Thu, 10 Jul 2008 20:02:18 -0400 (EDT) | From | Steven Rostedt <> | Subject | Re: [PATCH] ftrace: Documentation |
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On Thu, 10 Jul 2008, Randy Dunlap wrote:
> [I'm dropping good comments, just making more comments.]
This is why I CC'd you ;-)
> > > > + set_ftrace_notrace: This has the opposite effect that > > > + set_ftrace_filter has. Any function that is added > > > + here will not be traced. If a function exists > > > + in both set_ftrace_filter and set_ftrace_notrace > > > > (comma) > > > > > + the function will _not_ bet traced. > > be
Sorry, it has a gambling problem.
> > > > + stacktrace - This is one of the options that changes the trace itself. > > > > change > > changes :) [subject is "This", singular]
Woot! I'm actually right?? Nah, this can't be. Maybe my mom did speak good english. ;-)
> > > > > > + When a trace is recorded, so is the stack of functions. > > > + This allows for back traces of trace sites. > > > + > > > +sched_switch > > > +------------ > > > + > > > +This tracer simply records schedule switches. Here's an example > > > +on how to implement it. > > of
OK
> > > > > use? > > > > [...] > > > +Here we traced a 50 microsecond latency. But we also see all the > > > +functions that were called during that time. Note that enabling > > > > by enabling? > > > > > +function tracing we endure an added overhead. This overhead may > > > > (comma) > > > > > +extend the latency times. But never the less, this trace has provided > > nevertheless,
It is one word? I wrote that first and then thought that it was wrong.
> > > > +some very helpful debugging. > > > > debugging information?
Sure.
> > > > > + > > > + > > > +preemptoff > > > +---------- > > > + > > > +When preemption is disabled we may be able to receive interrupts but > > > > (comma) > > > > > +the task can not be preempted and a higher priority task must wait > > cannot
OK
> > > > +for preemption to be enabled again before it can preempt a lower > > > +priority task. > > > + > > > +The preemptoff tracer traces the places that disables preemption. > > > > disable > > > > > +Like the irqsoff, it records the maximum latency that preemption > > > +was disabled. The control of preemptoff is much like the irqsoff. > > > > > +Since this tracer only deals with RT tasks, we will run this slightly > > > +different than we did with the previous tracers. Instead of performing > > differently
OK
> > > > +an 'ls' we will run 'sleep 1' under 'chrt' which changes the > > > > (comma) > > > > > +priority of the task. > > > [...] > > > +Where as the setting of the NEED_RESCHED bit happens on the > > Whereas
OK
> > > > +task's stack. But because we are in a hard interrupt, the test > > ^? That's not a complete sentence.
I rewrote this part. So I'm not ignoring these comments.
> > > > +is with the interrupts stack which has that to be false. We don't > > interrupt > > > > ^^^^ > > Superfluous that? Don't understand that sentence. > > > > > +see the 'N' until we switch back to the task's stack. > > [...] > > > +When dynamic ftrace is initialized, it calls kstop_machine to make it > > ^^ what is "it"?
s/it/the machine/
> > > > +act like a uniprocessor so that it can freely modify code without > > > +worrying about other processors executing that same code. At > > > +initialization, the mcount calls are change to call a "record_ip" > > > > changed > > > > > +function. After this, the first time a kernel function is called, > > > +it has the calling address saved in a hash table. > > [...] > > > +Two files that contain to the enabling and disabling of recorded > > > +functions are: > > > > Can this be expressed somewhat differently? > > or drop "to".
I rewrote this part too.
> > > > > > + > > > + set_ftrace_filter > > > + > > > +and > > > + > > > + set_ftrace_notrace > > > + > > > +A list of available functions that you can add to this files is listed > > > > these > > > > > +in: > > > + > > > + available_filter_functions > > [...] > > > +Perhaps this isn't enough. The filters also allow simple wild cards. > > > +Only the following is currently available > > Only the following are currently available:
OK
> > > > + > > > + <match>* - will match functions that begins with <match> > > > > begin > > > > > + *<match> - will match functions that end with <match> > > > + *<match>* - will match functions that have <match> in it
Thanks Randy, once again you helped me out in my documentation.
-- Steve
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