# RESOLVED - How to make a task schedule faster? **URL:** \ **Category:** Uncategorized\ **Created:** [June 23, 2017, 10:18am UTC](https://discuss.px4.io/t/resolved-how-to-make-a-task-schedule-faster/3691 "2017-06-23T10:18:52Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![Darkus3](https://discuss.px4.io/user_avatar/discuss.px4.io/darkus3/32/1068_2.png) [@Darkus3](https://discuss.px4.io/u/Darkus3)\ **Post date:** [June 23, 2017, 10:18am UTC](https://discuss.px4.io/t/resolved-how-to-make-a-task-schedule-faster/3691/1 "2017-06-23T10:18:52Z")
All is on the title. > deamon\_task = px4\_task\_spawn\_cmd(“myserial”, > SCHED\_DEFAULT, > SCHED\_PRIORITY\_DEFAULT, > 3000, > myserial\_thread\_main, > (char \* const \*)&argv[0]); ---
**Author:** ![leoavelino](https://discuss.px4.io/letter_avatar_proxy/v4/letter/l/85e7bf/32.png) [@leoavelino](https://discuss.px4.io/u/leoavelino)\ **Post date:** [June 23, 2017, 11:58am UTC](https://discuss.px4.io/t/resolved-how-to-make-a-task-schedule-faster/3691/2 "2017-06-23T11:58:12Z")
Try replacing _SCHED\_PRIORITY\_DEFAULT_ by _SCHED\_PRIORITY\_MAX_ ---
**Author:** ![Darkus3](https://discuss.px4.io/user_avatar/discuss.px4.io/darkus3/32/1068_2.png) [@Darkus3](https://discuss.px4.io/u/Darkus3)\ **Post date:** [June 23, 2017, 12:12pm UTC](https://discuss.px4.io/t/resolved-how-to-make-a-task-schedule-faster/3691/3 "2017-06-23T12:12:32Z")
Yeah I already try to change the priority but it doesn’t make the task schedule faster at all… Here is my code: ``` int myserial_thread_main(int argc, char *argv[]) { char str[1000]={0}; char c='Q'; //UART open int uart = uart_init("/dev/ttyS6"); if(false == uart)return -1; if(false == set_uart_baudrate(uart,9600)){ printf("[YCM]set_uart_baudrate is failed\n"); return -1; } printf("[YCM]uart init is successful\n"); //QUEUE open -- does not work //mqd_t mqret = mq_open("xQueue",O_RDONLY); //UORB request /* subscribe to sensor_combined topic */ int sensor_sub_fd = orb_subscribe(ORB_ID(sensor_combined)); /* limit the update rate to 0.5 Hz */ orb_set_interval(sensor_sub_fd, 20); px4_pollfd_struct_t fds[] = { { .fd = sensor_sub_fd, .events = POLLIN }, /* there could be more file descriptors here, in the form like: * { .fd = other_sub_fd, .events = POLLIN }, */ }; //main thread loop while (!thread_should_exit) { //Receive from message queue "xQueue" // mq_receive(mqret, (void *) data, sizeof(data),NULL); int poll_ret = px4_poll(fds, 1, 20); if(poll_ret > 0){ if (fds[0].revents & POLLIN) { /* obtained data for the first file descriptor */ struct sensor_combined_s raw; /* copy sensors raw data into local buffer */ orb_copy(ORB_ID(sensor_combined), sensor_sub_fd, &raw); sprintf(str,"Ax %8.4f \n\r",(double)raw.accelerometer_m_s2[0]); sprintf(str + strlen(str),"Ay %8.4f \n\r",(double)raw.accelerometer_m_s2[1]); sprintf(str + strlen(str),"Az %8.4f \n\r",(double)raw.accelerometer_m_s2[2]); sprintf(str + strlen(str),"Gx %8.4f \n\r",(double)raw.gyro_rad[0]); sprintf(str + strlen(str),"Gy %8.4f \n\r",(double)raw.gyro_rad[1]); sprintf(str + strlen(str),"Gz %8.4f \n\r",(double)raw.gyro_rad[2]); for(int j=0;j **Author:** ![leoavelino](https://discuss.px4.io/letter_avatar_proxy/v4/letter/l/85e7bf/32.png) [@leoavelino](https://discuss.px4.io/u/leoavelino)\ **Post date:** [June 23, 2017, 12:37pm UTC](https://discuss.px4.io/t/resolved-how-to-make-a-task-schedule-faster/3691/4 "2017-06-23T12:37:30Z") Could you explain better what you mean by _task schedule faster_? What I understand from what you said (correct me if I am wrong) is that you want your task to be scheduled more often. ---
**Author:** ![Darkus3](https://discuss.px4.io/user_avatar/discuss.px4.io/darkus3/32/1068_2.png) [@Darkus3](https://discuss.px4.io/u/Darkus3)\ **Post date:** [June 23, 2017, 12:39pm UTC](https://discuss.px4.io/t/resolved-how-to-make-a-task-schedule-faster/3691/5 "2017-06-23T12:39:53Z")
Yeah thats what I meant, but despite incresing the system tick I don’t really know how to do it… Currently it’s approximativly each second… it’s really slow ---
**Author:** ![dagar](https://discuss.px4.io/user_avatar/discuss.px4.io/dagar/32/22_2.png) [@dagar](https://discuss.px4.io/u/dagar)\ **Post date:** [June 23, 2017, 2:05pm UTC](https://discuss.px4.io/t/resolved-how-to-make-a-task-schedule-faster/3691/6 "2017-06-23T14:05:01Z")
It’s not the scheduling it’s the polling within the loop, it’s waiting for new data from sensor\_combined, but it’s set to only update at 0.5 Hz. ``` /* limit the update rate to 0.5 Hz */ orb_set_interval(sensor_sub_fd, 20); ``` ---
**Author:** ![Darkus3](https://discuss.px4.io/user_avatar/discuss.px4.io/darkus3/32/1068_2.png) [@Darkus3](https://discuss.px4.io/u/Darkus3)\ **Post date:** [June 26, 2017, 8:50am UTC](https://discuss.px4.io/t/resolved-how-to-make-a-task-schedule-faster/3691/7 "2017-06-26T08:50:22Z")
> /\*\* > \* Set the minimum interval between which updates are seen for a subscription. > \* > \* If this interval is set, the subscriber will not see more than one update > \* within the period. > \* > \* Specifically, the first time an update is reported to the subscriber a timer > \* is started. The update will continue to be reported via poll and orb\_check, but > \* once fetched via orb\_copy another update will not be reported until the timer > \* expires. > \* > \* This feature can be used to pace a subscriber that is watching a topic that > \* would otherwise update too quickly. > \* > \* @param handle A handle returned from orb\_subscribe. > \* @param interval An interval period in milliseconds. > \* @return OK on success, ERROR otherwise with ERRNO set accordingly. > \*/ > int orb\_set\_interval(int handle, unsigned interval) ; IN uORBManager.hpp I beleived that to at first but here is the definition of this function and you see that the argv is definied in milisecond. So 50hz… Don’t beleive the commentary it’s a error due to past and copy EDIT I tried with those value : px4\_poll(fds, 1, 1) orb\_set\_interval(sensor\_sub\_fd, 1) (or like in px4\_simple\_app) px4\_poll(fds, 1,1000) orb\_set\_interval(sensor\_sub\_fd,200) and the periodicity is still around one seconde on the serial link. Is strange that it doesn’t seem to as an effect on it… I am stuck since three days on that… ---
**Author:** ![Darkus3](https://discuss.px4.io/user_avatar/discuss.px4.io/darkus3/32/1068_2.png) [@Darkus3](https://discuss.px4.io/u/Darkus3)\ **Post date:** [June 26, 2017, 9:29am UTC](https://discuss.px4.io/t/resolved-how-to-make-a-task-schedule-faster/3691/8 "2017-06-26T09:29:55Z")
and if I put orb\_set\_interval(sensor\_sub\_fd, 100000000) it’s really long ! So it have an influance on it but it seem that the faster it can get is 1000ms… I dont’t knoy why. Maybe my program require to much processing power ? It’s really strange… Maybe the upload rate of sensor data in the sensor\_combined is 1000ms ? Where can I found that ? ---
**Author:** ![leoavelino](https://discuss.px4.io/letter_avatar_proxy/v4/letter/l/85e7bf/32.png) [@leoavelino](https://discuss.px4.io/u/leoavelino)\ **Post date:** [June 26, 2017, 11:55am UTC](https://discuss.px4.io/t/resolved-how-to-make-a-task-schedule-faster/3691/9 "2017-06-26T11:55:51Z")
Try removing the _orb\_set\_interval_ so you can ideally schedule your task at the sensor\_combined topic sampling rate (considering your task is running with max. priority). ---
**Author:** ![Darkus3](https://discuss.px4.io/user_avatar/discuss.px4.io/darkus3/32/1068_2.png) [@Darkus3](https://discuss.px4.io/u/Darkus3)\ **Post date:** [June 26, 2017, 12:48pm UTC](https://discuss.px4.io/t/resolved-how-to-make-a-task-schedule-faster/3691/10 "2017-06-26T12:48:34Z")
1. The task is set to max priority : deamon\_task = px4\_task\_spawn\_cmd(“myserial”, SCHED\_DEFAULT, SCHED\_PRIORITY\_MAX, 3000, myserial\_thread\_main, (char \* const \*)&argv[0]); 2 . I removed the orb\_set\_interval and I put to 1ms px4\_poll(fds, 1, 1); And it still work at 1 second periodicity … ☹ I am sure now that its come directly from the update rate of the sensor\_combined topic. Were is set the upload rate of uORB message , via which timer ? Here is a screen of top command on the cpu : ![](https://discuss.px4.io/uploads/default/original/2X/6/608c97aacdf0e7816f38f52168adcec6f38a6383.png) My app “myserial” doesnt seem to require so much cpu resource compare to other task… and it is the highest priority it could have 255 , So it doesn’t come from this. Mybe changing the system tick ? #define SCHEDULE\_INTERVAL 2000 /\*\*\< The schedule interval in usec (500 Hz) \*/ (in /src/Firmware/src/drivers/px4fmu/fmu.cpp) Its already 500Hz… it’s enough normally. ---
**Author:** ![Darkus3](https://discuss.px4.io/user_avatar/discuss.px4.io/darkus3/32/1068_2.png) [@Darkus3](https://discuss.px4.io/u/Darkus3)\ **Post date:** [June 28, 2017, 9:22am UTC](https://discuss.px4.io/t/resolved-how-to-make-a-task-schedule-faster/3691/11 "2017-06-28T09:22:23Z")
any other idea ? I am really stuck here… ---
**Author:** ![Darkus3](https://discuss.px4.io/user_avatar/discuss.px4.io/darkus3/32/1068_2.png) [@Darkus3](https://discuss.px4.io/u/Darkus3)\ **Post date:** [June 28, 2017, 12:36pm UTC](https://discuss.px4.io/t/resolved-how-to-make-a-task-schedule-faster/3691/12 "2017-06-28T12:36:38Z")
Ok never mind , I started a new clean code with same principle and its work great… dont know were it was from… Danke ! CLOSED