why the clock() execution so time-consuming on EVM board

Huan Hou

Hi, all

I encounter a really strange problem. I want to profile our algorithm on EVM C6424, and when I use the clock() function for the profiler of several functions, the execution takes really a lot of time. But when I just read the TSCH and TSCL cycle counter instead of clock() function calls, the execution seems reasonable, about one tenth of the time consumed with clock() profilers. So can anyone explain to me why the time consumption differs so much?

By the way, I may call the clock() or read the TSCH, TSCL cycle counter 100 timers per frame, one frame corresponds to ~30ms playback.

Thanks for any reply.

Touse

over 13 years ago

0 RandyP over 13 years ago

TI__Guru* 84110 points

Touse,

Having never used this specific function myself, I would suggest you set a breakpoint at one of the calls to clock() and find out what it is doing. From the breakpoint, you can do a single-step into the function and look at its instructions in the Disassembler window.

The best option would be to use a macro for TSCH/TSCL. This will allow the optimizer to integrate those calls with the other instructions so more parallelism can be achieved.

Regards,
RandyP

0 Huan Hou over 13 years ago in reply to RandyP

Expert 1505 points

Hi, RandyP

I check the clock() function in rtslib,it just calls the HOSTclock below.

_CODE_ACCESS clock_t HOSTclock(void)
{
   clock_t result;
   _lock();

   writemsg(_DTGETCLK,parmbuf,NULL,0);
   readmsg(parmbuf, NULL);

   result = (clock_t)(UNLOAD32(parmbuf,0));
   _unlock();
   return result;
}

It seems it's also register reading just like the TSCH/TSCL registers. So my question is why the access of these timer register is much slower than the access of TSCH/TSCL registers when multiple clock() calls in a function?

Touse

0 RandyP over 13 years ago in reply to Huan Hou

TI__Guru* 84110 points

Touse,

I do not see the "register reading" in the source code above. I see "writemsg" and "readmsg" which sound a lot more complex. This may be the cause of the slower operation.

HOSTclock() sounds like a function that is going to return the time from the PC. That would be extremely slow, not anywhere near 10 times as slow as reading TSCH/TSCL.

My recommendation is to quit using the clock() function and use the TSCH/TSCL instead.

Regards,
RandyP

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0 Armstrong over 12 years ago in reply to RandyP

Intellectual 820 points

I agreed with RandyP.

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why the clock() execution so time-consuming on EVM board