如何在Vxworks中实现C定时器

Question

I have implemented timer functionality to find the performance of my task in windows and linux. But linux implementation is not working in Vxworks PPC 750 board. gettimeofday is not available in Vxworks.

t1 = vxworks_start_timer(); //How to implement ?
my_task();
t2 = vxworks_stop_timer(); //How to implement ?
elapsedtime = t2-t1;

How to implement this timer in Vxworks to calculate elapsed time of a task.

Answer 1

If the system timer tick resolution is sufficient, you could use tickGet() and sysClkRateGet() or clock_gettime() , but resolution is still limited to system clock tick

Otherwise, you could read TBL and TBU (arch-specific)

Answer 2

There are various approaches to this, dependant on your needs.

If the activity to be measured is long running, you might prefer to use the system tick counter, accessible via tickGet() or tickGet64() .

This increments at the system clock rate frequency (ie the rate of the scheduler, not the CPU freq), and so the resolution is limited to a single tick - which might be as large as 1/60th of a second. You can use sysClkRateGet() to determine the frequency.

For long running tasks, the above is probably sufficient, however if you require higher resolution, possibly at the expense of limited duration, you can use the system timestamp counter, if it is configured. For this, you can use sysTimestamp() (or sysTimestamp64() ), and also use sysTimestampFreq() to get the frequency.

Dependant on your system configuration, the counter may reset frequently, and you can use sysTimestampPeriod() to workout when this will occur - you will need to handle this in your timing code.

You can, of course, use both methods together to provide both a long running, yet high resolution timer