* Vernon Mauery <[EMAIL PROTECTED]> [2008-05-30 15:14:27]:
> I spent some time looking at the sched_latency test trying to see why it
> took so long to start the thread. The java version of the test takes
> a comparable amount of time to start the thread as it does for each period.
> The rt-test version was taking an order of magnitude longer. After digging
> through the java documentation, I found that the RealtimeThread does not
> actually start executing until the RealtimeThread.waitForNextPeriod()
> fulfills the time specified in the PeriodicParameters parameter included in
> its constructor. So all the tests are scheduled to run about 1 second
> after the threads are created. This gives the system plenty of time to
> create the thread (a non-realtime code path), set the scheduling parameters
> and then sleep until the specified run time. The start latency as measured
> by the test goes something like this:
>
> start_time = nanoTime() + 1000000000;
> rt = new realtimeThread(sched_param, new \
> PeriodicParameters(start_time, ...), ..., run);
>
> /* by the rtsj specification, this method will not run until start_time */
> run() {
> now = nanoTime();
> start_latency = now - start_time;
> ...
> }
>
> The rt-tests version went something like this:
>
> start_time = rt_gettime();
> create_fifo_thread(periodic_thread, (void*)0, PRIO);
>
> periodic_thread() {
> now = rt_gettime();
> start_latency = now - start;
> ...
> }
>
> As you can see, the start_latency is a very different measurement in these
> two cases. In the first, it is basically the initial starting latency as
> measured by the remainder of the loops. In the second, the execution path
> of creating the pthread is also counted in the latency. While this might
> be an important number for us to keep low in our testing, this is not what
> the java test is measuring.
>
> This patch puts the rt-test version in line with the java version. I also
> think this is reasonable since the rt-wiki says that we should _NEVER_
> create threads on the real-time stage.
>
> Signed-off-by: Vernon Mauery <[EMAIL PROTECTED]>
tested and
Acked-by: Chirag <[EMAIL PROTECTED]>
> diff --git a/testcases/realtime/func/sched_latency/sched_latency.c
> b/testcases/realtime/func/sched_latency/sched_latency.c
> index 021ee94..5c65704 100644
> --- a/testcases/realtime/func/sched_latency/sched_latency.c
> +++ b/testcases/realtime/func/sched_latency/sched_latency.c
> @@ -126,6 +126,9 @@ void *periodic_thread(void *arg)
> int failures = 0;
> nsec_t next = 0, now = 0, sched_delta = 0, delta = 0, prev = 0,
> iter_start;
>
> + /* wait for the specified start time */
> + rt_nanosleep_until(start);
> +
> now = rt_gettime();
> start_delay = (now - start)/NS_PER_US;
> iter_start = next = now;
> @@ -279,7 +282,8 @@ int main(int argc, char *argv[])
> exit(1);
> }
>
> - start = rt_gettime();
> + /* wait one quarter second to execute */
> + start = rt_gettime() + 250 * NS_PER_MS;
> per_id = create_fifo_thread(periodic_thread, (void*)0, PRIO);
>
> join_thread(per_id);
> diff --git a/testcases/realtime/include/librttest.h
> b/testcases/realtime/include/librttest.h
> index c298f34..dbc4ab0 100644
> --- a/testcases/realtime/include/librttest.h
> +++ b/testcases/realtime/include/librttest.h
> @@ -312,6 +312,10 @@ void nsec_to_ts(nsec_t ns, struct timespec *ts);
> */
> int ts_to_nsec(struct timespec *ts, nsec_t *ns);
>
> +/* rt_nanosleep: sleep until absolute time ns (in nanoseconds) using
> clock_nanosleep
> + */
> +void rt_nanosleep_until(nsec_t ns);
> +
> /* rt_nanosleep: sleep for ns nanoseconds using clock_nanosleep
> */
> void rt_nanosleep(nsec_t ns);
> diff --git a/testcases/realtime/lib/librttest.c
> b/testcases/realtime/lib/librttest.c
> index 703d6c8..20cb7a1 100644
> --- a/testcases/realtime/lib/librttest.c
> +++ b/testcases/realtime/lib/librttest.c
> @@ -398,6 +398,18 @@ void nsec_to_ts(nsec_t ns, struct timespec *ts)
> ts->tv_nsec = ns%NS_PER_SEC;
> }
>
> +void rt_nanosleep_until(nsec_t ns) {
> + struct timespec ts_sleep, ts_rem;
> + int rc;
> + nsec_to_ts(ns, &ts_sleep);
> + rc = clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME, &ts_sleep,
> &ts_rem);
> + /* FIXME: when should we display the remainder ? */
> + if (rc != 0) {
> + printf("WARNING: rt_nanosleep() returned early by %d s %d ns\n",
> + (int)ts_rem.tv_sec, (int)ts_rem.tv_nsec);
> + }
> +}
> +
> void rt_nanosleep(nsec_t ns) {
> struct timespec ts_sleep, ts_rem;
> int rc;
>
> There. I just inlined it using Message -> insert file. However, I think
> that
> will still word wrap the file if it is too long. So I am attaching the file
> as well.
>
> --Vernon
>
> > Signed-off-by: Vernon Mauery <[EMAIL PROTECTED]>
> >
> > --Vernon
>
>
> diff --git a/testcases/realtime/func/sched_latency/sched_latency.c
> b/testcases/realtime/func/sched_latency/sched_latency.c
> index 021ee94..5c65704 100644
> --- a/testcases/realtime/func/sched_latency/sched_latency.c
> +++ b/testcases/realtime/func/sched_latency/sched_latency.c
> @@ -126,6 +126,9 @@ void *periodic_thread(void *arg)
> int failures = 0;
> nsec_t next = 0, now = 0, sched_delta = 0, delta = 0, prev = 0,
> iter_start;
>
> + /* wait for the specified start time */
> + rt_nanosleep_until(start);
> +
> now = rt_gettime();
> start_delay = (now - start)/NS_PER_US;
> iter_start = next = now;
> @@ -279,7 +282,8 @@ int main(int argc, char *argv[])
> exit(1);
> }
>
> - start = rt_gettime();
> + /* wait one quarter second to execute */
> + start = rt_gettime() + 250 * NS_PER_MS;
> per_id = create_fifo_thread(periodic_thread, (void*)0, PRIO);
>
> join_thread(per_id);
> diff --git a/testcases/realtime/include/librttest.h
> b/testcases/realtime/include/librttest.h
> index c298f34..dbc4ab0 100644
> --- a/testcases/realtime/include/librttest.h
> +++ b/testcases/realtime/include/librttest.h
> @@ -312,6 +312,10 @@ void nsec_to_ts(nsec_t ns, struct timespec *ts);
> */
> int ts_to_nsec(struct timespec *ts, nsec_t *ns);
>
> +/* rt_nanosleep: sleep until absolute time ns (in nanoseconds) using
> clock_nanosleep
> + */
> +void rt_nanosleep_until(nsec_t ns);
> +
> /* rt_nanosleep: sleep for ns nanoseconds using clock_nanosleep
> */
> void rt_nanosleep(nsec_t ns);
> diff --git a/testcases/realtime/lib/librttest.c
> b/testcases/realtime/lib/librttest.c
> index 703d6c8..20cb7a1 100644
> --- a/testcases/realtime/lib/librttest.c
> +++ b/testcases/realtime/lib/librttest.c
> @@ -398,6 +398,18 @@ void nsec_to_ts(nsec_t ns, struct timespec *ts)
> ts->tv_nsec = ns%NS_PER_SEC;
> }
>
> +void rt_nanosleep_until(nsec_t ns) {
> + struct timespec ts_sleep, ts_rem;
> + int rc;
> + nsec_to_ts(ns, &ts_sleep);
> + rc = clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME, &ts_sleep,
> &ts_rem);
> + /* FIXME: when should we display the remainder ? */
> + if (rc != 0) {
> + printf("WARNING: rt_nanosleep() returned early by %d s %d ns\n",
> + (int)ts_rem.tv_sec, (int)ts_rem.tv_nsec);
> + }
> +}
> +
> void rt_nanosleep(nsec_t ns) {
> struct timespec ts_sleep, ts_rem;
> int rc;
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--
Cheers,
Chirag Jog
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