Hi Martin,

Thanks a lot.
I have tried to measure and print the performance counter value on as follows ( i.MX53QSB)

Trace::Timestamp start = Trace::timestamp();

my_funciton();

Trace::Timestamp end = Trace::timestamp();

printf("CPU_cyces= %lu\n",(end-start));

I have tried with printf(%zu), printf(%llu) and printf("%"PRIu32) format but the maximum number of digits what I can get is 10. I wonder what format can be used if the performance counter value is larger than 10 digits.
To calculate the elapsed time, I multiply the CPU_cycles by 1 nanosecod (ns) / cycle. Is that right?

Thanks,

On Tue, Sep 20, 2016 at 11:32 AM, Martin Stein <martin.stein@...1...> wrote:

Hi John,

Am 20.09.2016 um 01:46 schrieb John David:
> Dear Martin,
>
> Thanks a lot for your answers.
>
> I wanted to use the performance counter for more performance
> measurements such as cache-misses, but I don't know how to access and

I forgot to mention that you could also transform the performance
counter values into time values. On ARMv7 the counter counts every
single CPU cycle. Thus, you can use SECONDS = PERF_COUNTER / CPU_FREQUENCY.

> use it in the secure world userland. Could you please give me some

If you have the performance counter enabled in the SPECS, you can
include 'trace/timestamp.h' and read a timestamp via
'Genode::Trace::Timestamp Genode::Trace::timestamp();'.

> hints? is there any reading material on this?

I think [1] illustrates the use of the timestamp/performance counter
pretty good. The only document I could find to read about perfomance
counter access in general is the ARMv7 Manual [2] paragraph "C12.7
Counter access". If you have further questions, don't hesitate to ask.

Cheers,
Martin

[1] base-nova/src/test/platform/main.cc
[2]
http://liris.cnrs.fr/~mmrissa/lib/exe/fetch.php?media=armv7-a-r-manual.pdf

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