[dpdk-dev] Question about rte_manage_timer() and eal_intr_handle_interrupts

[Burakov, Anatoly]

On 02-Nov-18 4:00 AM, Somnath Kotur wrote:
> Hello,
>         I'm trying to launch a thread - lcore_mainloop( from
> examples/timer/main.c ) that runs rte_manage_timer() every 2s from testpmd
> to ensure the timers i've registered in my driver are checked for expiry  (
> i even tried putting this thread in my  driver as well,  no difference in
> results) and i see that while this thread is running, i somehow seem to
> stop getting interrupts ..infact i don't even
> see eal_intr_process_interrupts () being called.
> 
> 
> diff --git a/app/test-pmd/testpmd.c b/app/test-pmd/testpmd.c
> index ca4e1a4..a8d71d6 100644
> --- a/app/test-pmd/testpmd.c
> +++ b/app/test-pmd/testpmd.c
> @@ -71,6 +71,8 @@
>   #include <rte_pci.h>
>   #include <rte_ether.h>
>   #include <rte_ethdev.h>
> +#include <rte_cycles.h>
> +#include <rte_timer.h>
>   #include <rte_dev.h>
>   #include <rte_string_fns.h>
>   #ifdef RTE_LIBRTE_IXGBE_PMD
> @@ -2524,6 +2526,30 @@ signal_handler(int signum)
>          }
>   }
> 
> +static int
> +lcore_mainloop(__attribute__((unused)) void *arg)
> +{
> +       uint64_t prev_tsc = 0, cur_tsc, diff_tsc;
> +       unsigned int lcore_id;
> +
> +       lcore_id = rte_lcore_id();
> +       printf("Starting mainloop on core %u\n", lcore_id);
> +
> +       while (f_quit == 0) {
> +               cur_tsc = rte_rdtsc();
> +               diff_tsc = cur_tsc - prev_tsc;
> +               /* Schedule every 2 seconds */
> +               if (diff_tsc > rte_get_timer_hz() * 2) {
> +                       rte_timer_manage();
> +                       prev_tsc = cur_tsc;
> +               } else
> +                       sleep(1);
> +       }
> +       return 0;
> +}
> +
>   int
>   main(int argc, char** argv)
>   {
> @@ -2627,6 +2653,7 @@ main(int argc, char** argv)
>          if (strlen(cmdline_filename) != 0)
>                  cmdline_read_from_file(cmdline_filename);
> 
> +       rte_eal_remote_launch(lcore_mainloop, NULL, 3);
>          if (interactive == 1) {
>                  if (auto_start) {
>                          printf("Start automatic packet forwarding\n");
> 
> 
> My testpmd cmdline is like so:
> 
> testpmd -c 0xff -n 3 -- -i portmask=0x3 --nb-cores=3 --rxq=1 --txq=1
> 
> Any idea what could be the problem ? Is this something that is expected or
> am i doing something wrong ?
> 
> Thanks
> Som
> 

I may be completely off mark here, but as far as i understand, the EAL 
Alarm API uses the interrupt thread. The rte_timer API is a high 
performance timer API and is meant to be managed manually, by 
periodically[1] calling rte_timer_manage(). If you want something to be 
called every two seconds, just set up an rte_alarm - there's no need to 
use the timer API (unless you are on FreeBSD, where alarm API is not 
officially supported).

[1] as in, more frequently than every two seconds if you want to have 
any semblance of timer precision!

-- 
Thanks,
Anatoly