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Add small randomness to spacing between samples for one server

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This commit is contained in:
Miroslav Lichvar 2010-12-09 16:06:42 +01:00
parent d1b820e7e3
commit 833022b745
4 changed files with 26 additions and 6 deletions
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4
broadcast.c
View file

@ -121,7 +121,7 @@ timeout_handler(void *arbitrary)
/* Requeue timeout. Don't care if interval drifts gradually, so just do it
* at the end. */
SCH_AddTimeoutInClass((double) d->interval, 1.0,
SCH_AddTimeoutInClass((double) d->interval, 1.0, 0.02,
SCH_NtpBroadcastClass,
timeout_handler, (void *) d);
@ -148,7 +148,7 @@ BRD_AddDestination(IPAddr *addr, unsigned short port, int interval)
destinations[n_destinations].addr.port = port;
destinations[n_destinations].interval = interval;
SCH_AddTimeoutInClass((double) interval, 1.0,
SCH_AddTimeoutInClass((double) interval, 1.0, 0.0,
SCH_NtpBroadcastClass,
timeout_handler, (void *)(destinations + n_destinations));

9
ntp_core.c
View file

@ -178,6 +178,9 @@ struct NCR_Instance_Record {
minimise risk of network collisions) (in seconds) */
#define SAMPLING_SEPARATION 0.2
/* Randomness added to spacing between samples for one server/peer */
#define SAMPLING_RANDOMNESS 0.02
/* Spacing between samples in burst mode for one server/peer */
#define BURST_INTERVAL 2.0
@ -247,6 +250,7 @@ start_initial_timeout(NCR_Instance inst)
/* Start timer for first transmission */
inst->timeout_id = SCH_AddTimeoutInClass(INITIAL_DELAY, SAMPLING_SEPARATION,
SAMPLING_RANDOMNESS,
SCH_NtpSamplingClass,
transmit_timeout, (void *)inst);
inst->timer_running = 1;
@ -622,6 +626,7 @@ transmit_timeout(void *arg)
/* Requeue timeout */
inst->timer_running = 1;
inst->timeout_id = SCH_AddTimeoutInClass(WARM_UP_DELAY, SAMPLING_SEPARATION,
SAMPLING_RANDOMNESS,
SCH_NtpSamplingClass,
transmit_timeout, (void *)inst);
@ -707,6 +712,7 @@ transmit_timeout(void *arg)
if (do_timer) {
inst->timer_running = 1;
inst->timeout_id = SCH_AddTimeoutInClass(timeout_delay, SAMPLING_SEPARATION,
SAMPLING_RANDOMNESS,
SCH_NtpSamplingClass,
transmit_timeout, (void *)inst);
} else {
@ -1259,6 +1265,7 @@ receive_packet(NTP_Packet *message, struct timeval *now, double now_err, NCR_Ins
/* Get rid of old timeout and start a new one */
SCH_RemoveTimeout(inst->timeout_id);
inst->timeout_id = SCH_AddTimeoutInClass(delay_time, SAMPLING_SEPARATION,
SAMPLING_RANDOMNESS,
SCH_NtpSamplingClass,
transmit_timeout, (void *)inst);
}
@ -1818,6 +1825,7 @@ NCR_InitiateSampleBurst(NCR_Instance inst, int n_good_samples, int n_total_sampl
}
inst->timer_running = 1;
inst->timeout_id = SCH_AddTimeoutInClass(0.0, SAMPLING_SEPARATION,
SAMPLING_RANDOMNESS,
SCH_NtpSamplingClass,
transmit_timeout, (void *) inst);
break;
@ -1831,6 +1839,7 @@ NCR_InitiateSampleBurst(NCR_Instance inst, int n_good_samples, int n_total_sampl
}
inst->timer_running = 1;
inst->timeout_id = SCH_AddTimeoutInClass(0.0, SAMPLING_SEPARATION,
SAMPLING_RANDOMNESS,
SCH_NtpSamplingClass,
transmit_timeout, (void *) inst);
break;

14
sched.c
View file

@ -129,6 +129,7 @@ handle_slew(struct timeval *raw,
void
SCH_Initialise(void)
{
struct timeval tv;
FD_ZERO(&read_fds);
n_read_fds = 0;
@ -143,6 +144,9 @@ SCH_Initialise(void)
LCL_AddParameterChangeHandler(handle_slew, NULL);
LCL_ReadRawTime(&tv);
srandom(tv.tv_sec * tv.tv_usec);
initialised = 1;
return;
@ -322,17 +326,23 @@ SCH_AddTimeoutByDelay(double delay, SCH_TimeoutHandler handler, SCH_ArbitraryArg
/* ================================================== */
SCH_TimeoutID
SCH_AddTimeoutInClass(double min_delay, double separation,
SCH_AddTimeoutInClass(double min_delay, double separation, double randomness,
SCH_TimeoutClass class,
SCH_TimeoutHandler handler, SCH_ArbitraryArgument arg)
{
TimerQueueEntry *new_tqe;
TimerQueueEntry *ptr;
struct timeval now;
double diff;
double diff, r;
double new_min_delay;
assert(initialised);
if (randomness > 0.0) {
r = random() % 0xffff / (0xffff - 1.0) * randomness + 1.0;
min_delay *= r;
separation *= r;
}
LCL_ReadRawTime(&now);
new_min_delay = min_delay;

5
sched.h
View file

@ -72,8 +72,9 @@ extern SCH_TimeoutID SCH_AddTimeoutByDelay(double delay, SCH_TimeoutHandler, SCH
/* This queues a timeout in a particular class, ensuring that the
expiry time is at least a given separation away from any other
timeout in the same class */
extern SCH_TimeoutID SCH_AddTimeoutInClass(double min_delay, double separation,
timeout in the same class, given randomness is added to the delay
and separation */
extern SCH_TimeoutID SCH_AddTimeoutInClass(double min_delay, double separation, double randomness,
SCH_TimeoutClass class,
SCH_TimeoutHandler handler, SCH_ArbitraryArgument);