On Tue, Oct 4, 2011 at 7:16 AM, Gilles Chanteperdrix
<[email protected]> wrote:
> I am sorry, I do not really understand what you are doing, what has
> CONFIG_HZ to do with your issue?
I was wondering if this configuration item may have an impact on the
kernel scheduling speed.
> Could you post a self-contained example allowing to reproduce the issue
> you observe?
So, basically, I just create a start a native xenomai thread :
rt_task_create(&task, "Read IO Card", 0, 99, T_FPU);
rt_task_start (&task, &polling_task, 0);
And then, the task itself performs a loop that acquires data on a
periodic basis of 1ms (see code below).
The problem is that when I run the code, the value of missed in either
1 or 2, meaning that the deadline expired and the task does not meet
its timing requirements.
So, if you have any suggestion/comments to improve this code or how
kernel configuration may impact the performance of such piece of code,
it would be very interesting.
void polling_task(void * arg)
{
int i;
double tmp;
int ret;
uint8_t raw[128 * 16];
double rate = 0.0001;
int result;
unsigned long missed;
a4l_insn_t insn_tab[16];
a4l_insnlst_t insnlst;
insnlst.count = 16;
insnlst.insns = insn_tab;
for (i=0; i<16; i++)
{
insn_tab[i].type = A4L_INSN_READ;
insn_tab[i].idx_subd = 0;
insn_tab[i].chan_desc = chdesc[i];
insn_tab[i].data_size = 8;
insn_tab[i].data = &raw[128 * i];
}
rt_task_set_periodic(NULL, TM_NOW, rate * 1000000000.0);
rt_task_set_mode (0,T_LOCK|T_PRIMARY|T_NOSIG|T_RPIOFF, NULL);
while(1)
{
result = rt_task_wait_period(&missed);
if (result == -ETIMEDOUT)
{
printf("Number of missed deadlines: %lu \n", missed);
}
ret = a4l_snd_insnlist(&device, &insnlst);
if (ret != 0)
{
printf("insnlist error: %d \n", ret);
}
for (i=0; i<16; i++)
{
ret = a4l_rawtod (chinfos[i], rnginfos[i], &tmp, &raw[i*128], 1);
if (ret <= 0)
{
printf("rawtod() error: %d\n", ret);
}
}
return;
}
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