Well, I didn't mention that because I can't guess why. However, I had what could be a similar thing before, but with Leon3 implemented on the logic of the Zedboard. When I traced down the BSP code (which wasn't RTEMS, I used the bcc there as far as I remember) it really didn't contain anything that would make the measurements differ if you changed the number of ticks per microsecond. So if it's a similar reason, you could figure it out by tracing the code from the top RTEMS api's down to the Board support package. On Mar 27, 2018 14:02, "BRIARD Sebastien" < sebastien.bri...@thalesaleniaspace.com> wrote:
> Good point. Thanks. > > Would you have any idea concerning my other question ? (why I get the same > result for interrupt latency with different values of Tick per microsecond ) > > > > *De :* Rehab Massoud [mailto:rehab.mass...@gmail.com] > *Envoyé :* mardi 27 mars 2018 13:57 > *À :* BRIARD Sebastien > *Cc :* rtems-us...@rtems.org > *Objet :* RE: Interrupt latency in RTEMS (Zedboard) > > > > Needless to say also you can't measure software execution time that > accurately with software. It's not only that it's intrusive but also would > never be cycle accurate. If you really need such cycle accuracy you might > think about hardware-based tracing techniques. > > On Mar 27, 2018 13:52, "BRIARD Sebastien" <sebastien.briard@ > thalesaleniaspace.com> wrote: > > Yeah, hardware limits to 1.5ns if we take in account the max frequency of > the cortex. (That was the more or less 1ns =) ) > > > > *De :* Rehab Massoud [mailto:rehab.mass...@gmail.com] > *Envoyé :* mardi 27 mars 2018 13:49 > *À :* BRIARD Sebastien; rtems-us...@rtems.org > *Objet :* Re: Interrupt latency in RTEMS (Zedboard) > > > > Hi, the smaller theoretical delay accuracy you can measure (without adding > to an ASIC cascaded FF) is one clock cycle. I think the maximum frequency > that could be achieved on zedboard is not more than 800 MHz, and the > maximum Zync's Cortex freq per Zedboard's datasheet is 667 MHz, which means > you can't achieve 1 nanosecond accuracy even with hardware measurements, > right? > > On Mar 27, 2018 13:30, "BRIARD Sebastien" <sebastien.briard@ > thalesaleniaspace.com> wrote: > > > > > > *De :* BRIARD Sebastien > *Envoyé :* mardi 27 mars 2018 11:42 > *À :* 'users@rtems.org' > *Objet :* Interrupt latency in RTEMS (Zedboard) > > > > Hi, > > > > I was trying to measure the interrupt latency in RTEMS with a Xilinx Zynq > Zedboard (cortex A9). > I modified the c file in classic_signal example to measure time in the > main loop and right after entering the handler. > That might seem artificial but well, it gives me a value with a relatively > simple code. > > I used this code for 100, 10000, and one million ticks per second. I am > trying to understand how the measure can quite equal with 100 ticks per > second and a million. > (I obtained values between 500ns and 1000ns). > Is there another timer that is used for interrupt processing ? > > A subsequent question, is it possible to use a larger value than a tick > per microsecond ? Maybe I am confusing a little between frequency and tick > clock in RTEMS but I would like to run test with more or less a tick per > nanosecond. > > Thank you, > Sébastien. > > > _______________________________________________ > users mailing list > users@rtems.org > http://lists.rtems.org/mailman/listinfo/users >
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