Re: Ftrace Data Export

[Chunyan Zhang]

Hi Felipe,

On 17 May 2017 at 16:08, Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx> wrote:
>
> Hi Chunyan,
>
> When you wrote your patchset to provide ftrace exports, why did you
> choose to export only function trace? Why not tracepoints,

In fact, I tried submitting patches[1] to do exporting tracepoint to
STM, but Ingo and Steven commented that would introduce certain amount
of overhead, and that was not acceptable. I also used
'benchmark_event' to see the additional overhead caused by printing
tracepoint message to STM.  I cannot remember the exact data though,
the increased time consuming indeed was non-ignorable.

So at the end I gave up that idea, and later on switched to the way of
implementation you see in the kernel now.

> function_graph, hwlat, irqsoff and all the other possibilities?

I haven't thought about these clear enough :)
Any suggestion?

Thanks,
Chunyan

[1] https://lkml.org/lkml/2015/7/7/230

>
> Is there an underlying reason why you chose to export only function
> trace?
>
> Thanks
>
> --
> balbi