diff --git a/lib/hooks/jitter_calc.c b/lib/hooks/jitter_calc.c new file mode 100644 index 000000000..a2aeda9f6 --- /dev/null +++ b/lib/hooks/jitter_calc.c @@ -0,0 +1,84 @@ +/** Calc jitter, mean and variance of GPS vs NTP TS. + * + * @author Umar Farooq + * @copyright 2017, Institute for Automation of Complex Power Systems, EONERC + *********************************************************************************/ + +/** @addtogroup hooks Hook functions + * @{ + */ + +#include "hook.h" +#include "plugin.h" +#include "timing.h" + +#define CALC_GPS_NTP_DELAY 0 /* @todo move to global config file */ +#define GPS_NTP_DELAY_WIN_SIZE 16 + +static int64_t jitter_val[GPS_NTP_DELAY_WIN_SIZE] = {0}; +static int64_t delay_series[GPS_NTP_DELAY_WIN_SIZE] = {0}; +static int64_t moving_avg[GPS_NTP_DELAY_WIN_SIZE] = {0}; +static int64_t moving_var[GPS_NTP_DELAY_WIN_SIZE] = {0}; +static int64_t delay_mov_sum = 0, delay_mov_sum_sqrd = 0; +static int curr_count = 0; + +/** + * Hook to calculate jitter between GTNET-SKT GPS timestamp and Villas node NTP timestamp. + * + * Drawbacks: No protection for out of order packets. Default positive delay assumed, + * so GPS timestamp should be earlier than NTP timestamp. If difference b/w NTP and GPS ts + * is high (i.e. several mins depending on GPS_NTP_DELAY_WIN_SIZE), + * the variance value will overrun the 64bit value. + */ +int hook_jitter_ts(struct hook *h, struct sample *smps[], size_t *cnt) +{ + /* @todo save data for each node, not just displaying on the screen, doesn't work for more than one node!!! */ + struct timespec now = time_now(); + int64_t delay_sec, delay_nsec, curr_delay_us; + + for(int i = 0; i < *cnt; i++) { + delay_sec = now.tv_sec - smps[i]->ts.origin.tv_sec; + delay_nsec = now.tv_nsec - smps[i]->ts.origin.tv_nsec; + + /* Calc on microsec instead of nenosec delay as variance formula overflows otherwise.*/ + curr_delay_us = delay_sec*1000000 + delay_nsec/1000; + + delay_mov_sum = delay_mov_sum + curr_delay_us - delay_series[curr_count]; + moving_avg[curr_count] = delay_mov_sum/(GPS_NTP_DELAY_WIN_SIZE); /* Will be valid after GPS_NTP_DELAY_WIN_SIZE initial values */ + + delay_mov_sum_sqrd = delay_mov_sum_sqrd + (curr_delay_us*curr_delay_us) - (delay_series[curr_count]*delay_series[curr_count]); + moving_var[curr_count] = (delay_mov_sum_sqrd - (delay_mov_sum*delay_mov_sum)/GPS_NTP_DELAY_WIN_SIZE)/(GPS_NTP_DELAY_WIN_SIZE-1); + + delay_series[curr_count] = curr_delay_us; /* Update the last delay value */ + + /* Jitter calc formula as used in Wireshark according to RFC3550 (RTP) + D(i,j) = (Rj-Ri)-(Sj-Si) = (Rj-Sj)-(Ri-Si) + J(i) = J(i-1)+(|D(i-1,i)|-J(i-1))/16 + */ + jitter_val[(curr_count+1)%GPS_NTP_DELAY_WIN_SIZE] = jitter_val[curr_count] + (abs(curr_delay_us) - jitter_val[curr_count])/16; + + info("jitter %ld usec, moving average %ld usec, moving variance %ld usec\n", jitter_val[(curr_count+1)%GPS_NTP_DELAY_WIN_SIZE], moving_avg[curr_count], moving_var[curr_count]); + + curr_count++; + if(curr_count >= GPS_NTP_DELAY_WIN_SIZE) + curr_count = 0; + } + return 0; +} + +#if CALC_GPS_NTP_DELAY == 1 +static struct plugin p = { + .name = "jitter_calc", + .description = "Calc jitter, mean and variance of GPS vs NTP TS", + .type = PLUGIN_TYPE_HOOK, + .hook = { + .priority = 0, + .builtin = true, + .read = hook_jitter_ts, + } +}; + +REGISTER_PLUGIN(&p) +#endif + +/** @} */