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SubjectRe: [PATCH 1/2 v2] tracing/function-graph-tracer: various fixes and features

* Frederic Weisbecker <fweisbec@gmail.com> wrote:

>
> This patch brings various bugfixes:
>
> _ Drop the first irrelevant task switch on the very beginning of a trace.
> _ Drop the OVERHEAD word from the headers, the DURATION word is sufficient and will not
> overlap other columns.
> _ Make the headers fit well their respective columns whatever the selected options.

> About features, one can now disable the duration (this will hide the
> overhead too for convenient reasons and because on doesn't need overhead
> if it hasn't the duration

very nice! I've applied this to tip/tracing/function-graph-tracer, thanks
Frederic!

this:

> I guess no one needs the nanosec precision here, the main goal is to
> find when happened the events on a cpu when the trace switches from one
> cpu to another.
>
> ie:
>
> 274.874760 | 1) 0.676 us | _spin_unlock();
> 274.874762 | 1) 0.609 us | native_load_sp0();
> 274.874763 | 1) 0.602 us | native_load_tls();
> 274.878739 | 0) 0.722 us | }
> 274.878740 | 0) 0.714 us | native_pmd_val();
> 274.878741 | 0) 0.730 us | native_pmd_val();
>
> Here there is a 4000 usecs difference when we switch the cpu.

Still needs a solution - if we do cross-CPU traces we want to have a
global trace clock with 'seemless' transition between CPUs.

Ingo


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