Thanks.
On Mon, 2008-08-18 at 13:34 -0500, Will Schmidt wrote:
> This is a patch from John, written a few months back. I have fixed up a
> few cosmetic whitespace bits, and have refreshed it so it should apply
> cleanly to LTP today.
>
> Comments originally by John Stultz:
>
> So I've been trying to go through and review our test cases to make sure
> we're getting sane data and the tests are really testing what we want.
>
> Looking at gtod_latency and gtod_infinite, I was always struck that
> gtod_infinite always came up with much larger latencies while
> gtod_latency usually seemed to miss them.
>
> Main issues:
>
> 1) gtod_latency was not running for long enough, I've upped the
> iterations by 10x to make sure we get more solid results.
>
> 2) gtod_latency was doing too much computation between gtod calls. This
> means it could miss latencies that occur while it was running. I
> reworked the data collection loop so the un-measured window is smaller.
>
> 3) gtod_infinite was accidentally measuring its own computation in its
> delay, inflating its values. I cut that logic out.
>
> 4) both gtod_latency and gtod_infinite were not running mlocked. this
> caused background SCHED_OTHER disk access to inject delays, making the
> results less reliable.
>
> Those four issues have been fixed, and I also converted gtod_latency to
> use clock_gettime() just to be consistent and to give slightly better
> resolution.
>
> -john
>
> Signed-off-by: John Stultz <[EMAIL PROTECTED]>
> Acked-by: Darren Hart <[EMAIL PROTECTED]>
> Acked-by: Will Schmidt <[EMAIL PROTECTED]>
A Real Time test case patch after long time. Patch is merged.
Regards--
Subrata
>
> ---
>
> diff -Naur ltp.orig/testcases/realtime/func/gtod_latency/gtod_infinite.c
> ltp/testcases/realtime/func/gtod_latency/gtod_infinite.c
> --- ltp.orig/testcases/realtime/func/gtod_latency/gtod_infinite.c
> 2008-08-18 13:15:21.000000000 -0500
> +++ ltp/testcases/realtime/func/gtod_latency/gtod_infinite.c 2008-08-18
> 12:22:23.000000000 -0500
> @@ -53,6 +53,7 @@
> #include <sched.h>
> #include <librttest.h>
> #include <libjvmsim.h>
> +#include <sys/mman.h>
>
> /* #define CLOCK_TO_USE CLOCK_MONOTONIC */
> #define CLOCK_TO_USE CLOCK_REALTIME
> @@ -66,9 +67,9 @@
> void usage(void)
> {
> rt_help();
> - printf("gtod_infinite specific options:\n");
> - printf(" -j enable jvmsim\n");
> - printf(" -wWINDOW iterations in max value window (default
> inf)\n");
> + printf("gtod_infinite specific options:\n");
> + printf(" -j enable jvmsim\n");
> + printf(" -wWINDOW iterations in max value window (default
> inf)\n");
> }
>
> int parse_args(int c, char *v)
> @@ -121,9 +122,11 @@
> printf("jvmsim disabled\n");
> }
>
> + mlockall(MCL_CURRENT|MCL_FUTURE);
> +
> if (max_window > 0) {
> - printf("%d iterations in max calculation window\n",
> - max_window);
> + printf("%d iterations in max calculation window\n",
> + max_window);
> }
>
> param.sched_priority = sched_get_priority_min(SCHED_FIFO) + 80;
> @@ -141,6 +144,7 @@
>
> wi = 0;
> while(1) {
> + rc = clock_gettime(CLOCK_TO_USE, &p_ts);
> rc = clock_gettime(CLOCK_TO_USE, &ts);
> if (rc) {
> perror("clock_gettime");
> @@ -153,11 +157,11 @@
> diff_time = e_time - s_time;
>
> if (max_window > 0 ||
> - ((diff_time > max_time) ||
> + ((diff_time > max_time) ||
> (diff_time > REPORT_MIN))) {
> if (diff_time > max_time)
> max_time = diff_time;
> -
> +
> if (max_window == 0 || ++wi == max_window) {
> tt = (time_t)ts.tv_sec;
> printf("Task delayed for %lld nsec!!! %s",
> @@ -170,13 +174,6 @@
> }
> }
>
> - rc = clock_gettime(CLOCK_TO_USE, &p_ts);
> - if (rc) {
> - perror("clock_gettime");
> - exit(1);
> - }
> - } else {
> - p_ts = ts;
> }
> }
> return 0;
> diff -Naur ltp.orig/testcases/realtime/func/gtod_latency/gtod_latency.c
> ltp/testcases/realtime/func/gtod_latency/gtod_latency.c
> --- ltp.orig/testcases/realtime/func/gtod_latency/gtod_latency.c
> 2008-08-18 13:15:21.000000000 -0500
> +++ ltp/testcases/realtime/func/gtod_latency/gtod_latency.c 2008-08-18
> 12:22:10.000000000 -0500
> @@ -54,8 +54,9 @@
> #include <limits.h>
> #include <libstats.h>
> #include <librttest.h>
> +#include <sys/mman.h>
>
> -#define ITERATIONS 1000000
> +#define ITERATIONS 10000000
> #define HIST_BUCKETS 20
>
> #define SCATTER_FILENAME 0
> @@ -202,19 +203,20 @@
> }
>
>
> -/* return difference in microseconds */
> -unsigned long long tv_minus(struct timeval *tv_start, struct timeval *tv_end)
> +long long timespec_subtract(struct timespec * a, struct timespec *b)
> {
> - unsigned long long usecs;
> - usecs = (tv_end->tv_sec - tv_start->tv_sec) * 1000000;
> - usecs += tv_end->tv_usec - tv_start->tv_usec;
> - return usecs;
> + long long ns;
> + ns = (b->tv_sec - a->tv_sec) * 1000000000LL;
> + ns += (b->tv_nsec - a->tv_nsec);
> + return ns;
> }
>
> +struct timespec start_data[ITERATIONS];
> +struct timespec stop_data[ITERATIONS];
> +
> int main(int argc, char *argv[])
> {
> int i, err;
> - struct timeval tv_a, tv_b;
> unsigned long long delta;
> unsigned long long max, min;
> struct sched_param param;
> @@ -227,6 +229,8 @@
> stats_quantiles_init(&quantiles, (int)log10(ITERATIONS));
> setup();
>
> + mlockall(MCL_CURRENT|MCL_FUTURE);
> +
> if (stats_cmdline(argc, argv) < 0) {
> printf("usage: %s help\n", argv[0]);
> exit(1);
> @@ -242,7 +246,7 @@
> fprintf(stderr, "This program runs with a scheduling
> policy of SCHED_FIFO at priority %d\n", param.sched_priority);
> fprintf(stderr, "You don't have the necessary
> privileges to create such a real-time process.\n");
> } else {
> - fprintf(stderr, "Failed to set scheduler, errno %d\n",
> errno);
> + fprintf(stderr, "Failed to set scheduler, errno %d\n",
> errno);
> }
> exit(1);
> }
> @@ -259,9 +263,11 @@
> latency_trace_start();
> }
> for (i = 0; i < ITERATIONS; i++) {
> - gettimeofday(&tv_a, NULL);
> - gettimeofday(&tv_b, NULL);
> - delta = tv_minus(&tv_a, &tv_b);
> + clock_gettime(CLOCK_MONOTONIC,&start_data[i]);
> + clock_gettime(CLOCK_MONOTONIC,&stop_data[i]);
> + }
> + for (i = 0; i < ITERATIONS; i++) {
> + delta = timespec_subtract(&start_data[i], &stop_data[i]);
> dat.records[i].x = i;
> dat.records[i].y = delta;
> if (i == 0 || delta < min) min = delta;
> @@ -273,7 +279,7 @@
> latency_trace_stop();
> if (i != ITERATIONS) {
> printf("Latency threshold (%lluus) exceeded at
> iteration %d\n",
> - latency_threshold, i);
> + latency_threshold, i);
> latency_trace_print();
> stats_container_resize(&dat, i + 1);
> }
> @@ -281,19 +287,18 @@
>
> stats_hist(&hist, &dat);
> stats_container_save(filenames[SCATTER_FILENAME], titles[SCATTER_TITLE],
> - labels[SCATTER_LABELX], labels[SCATTER_LABELY],
> &dat, "points");
> + labels[SCATTER_LABELX], labels[SCATTER_LABELY],
> &dat, "points");
> stats_container_save(filenames[HIST_FILENAME], titles[HIST_TITLE],
> - labels[HIST_LABELX], labels[HIST_LABELY], &hist,
> "steps");
> + labels[HIST_LABELX], labels[HIST_LABELY],
> &hist, "steps");
>
> /* report on deltas */
> - printf("Min: %llu us\n", min);
> - printf("Max: %llu us\n", max);
> - printf("Avg: %.4f us\n", stats_avg(&dat));
> - printf("StdDev: %.4f us\n", stats_stddev(&dat));
> + printf("Min: %llu ns\n", min);
> + printf("Max: %llu ns\n", max);
> + printf("Avg: %.4f ns\n", stats_avg(&dat));
> + printf("StdDev: %.4f ns\n", stats_stddev(&dat));
> printf("Quantiles:\n");
> stats_quantiles_calc(&dat, &quantiles);
> stats_quantiles_print(&quantiles);
>
> -
> return 0;
> }
>
>
>
>
> -------------------------------------------------------------------------
> This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
> Build the coolest Linux based applications with Moblin SDK & win great prizes
> Grand prize is a trip for two to an Open Source event anywhere in the world
> http://moblin-contest.org/redirect.php?banner_id=100&url=/
> _______________________________________________
> Ltp-list mailing list
> [email protected]
> https://lists.sourceforge.net/lists/listinfo/ltp-list
-------------------------------------------------------------------------
This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
Build the coolest Linux based applications with Moblin SDK & win great prizes
Grand prize is a trip for two to an Open Source event anywhere in the world
http://moblin-contest.org/redirect.php?banner_id=100&url=/
_______________________________________________
Ltp-list mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/ltp-list
