cyclictest: ARM panda clock resolution will be ~30 usec unless
CONFIG_OMAP_32K_TIMER=n, resulting in a poor latency report.
This patch does _not_ fix the problem, it merely provides the
instrumentation to make it visible. The value of measured
resolution is useful information for any system.
Signed-off-by: Frank Rowand <frank.rowand@xxxxxxxxxxx>
---
src/cyclictest/cyclictest.c | 87 86 + 1 - 0 !
1 file changed, 86 insertions(+), 1 deletion(-)
Index: b/src/cyclictest/cyclictest.c
===================================================================
--- a/src/cyclictest/cyclictest.c
+++ b/src/cyclictest/cyclictest.c
@@ -171,6 +171,7 @@ static int duration = 0;
static int use_nsecs = 0;
static int refresh_on_max;
static int force_sched_other;
+static int check_clock_resolution_loops = 0;
static pthread_cond_t refresh_on_max_cond = PTHREAD_COND_INITIALIZER;
static pthread_mutex_t refresh_on_max_lock = PTHREAD_MUTEX_INITIALIZER;
@@ -854,6 +855,9 @@ static void display_help(int error)
"-P --preemptoff Preempt off tracing (used with -b)\n"
"-q --quiet print only a summary on exit\n"
"-r --relative use relative timer instead of absolute\n"
+ "-R LOOP --resolution=LOOP check clock resolution, calling clock_gettime() LOOP\n"
+ " times. list of clock_gettime() values will be\n"
+ " reported with -v\n"
"-s --system use sys_nanosleep and sys_setitimer\n"
"-t --threads one thread per available processor\n"
"-t [NUM] --threads=NUM number of threads:\n"
@@ -982,6 +986,7 @@ static void process_options (int argc, c
{"preemptoff", no_argument, NULL, 'P'},
{"quiet", no_argument, NULL, 'q'},
{"relative", no_argument, NULL, 'r'},
+ {"resolution", required_argument, NULL, 'R'},
{"system", no_argument, NULL, 's'},
{"threads", optional_argument, NULL, 't'},
{"unbuffered", no_argument, NULL, 'u'},
@@ -996,7 +1001,7 @@ static void process_options (int argc, c
{"numa", no_argument, NULL, 'U'},
{NULL, 0, NULL, 0}
};
- int c = getopt_long(argc, argv, "a::b:Bc:Cd:e:Efh:H:i:Il:MnNo:O:p:PmqrsSt::uUvD:wWT:y:",
+ int c = getopt_long(argc, argv, "a::b:Bc:Cd:e:Efh:H:i:Il:MnNo:O:p:PmqrR:sSt::uUvD:wWT:y:",
long_options, &option_index);
if (c == -1)
break;
@@ -1061,6 +1066,14 @@ static void process_options (int argc, c
break;
case 'q': quiet = 1; break;
case 'r': timermode = TIMER_RELTIME; break;
+ case 'R':
+ {
+ char *endptr;
+ check_clock_resolution_loops = strtol(optarg, &endptr, 10);
+ if ((endptr == optarg) || !check_clock_resolution_loops)
+ check_clock_resolution_loops = -1;
+ }
+ break;
case 's': use_system = MODE_SYS_OFFSET; break;
case 't':
if (smp) {
@@ -1132,6 +1145,11 @@ static void process_options (int argc, c
} else if (tracelimit)
fileprefix = procfileprefix;
+ if (check_clock_resolution_loops == -1) {
+ warn("-R requires positive integer value for LOOP\n");
+ error = 1;
+ }
+
if (clocksel < 0 || clocksel > ARRAY_SIZE(clocksources))
error = 1;
@@ -1391,6 +1409,73 @@ int main(int argc, char **argv)
if (check_timer())
warn("High resolution timers not available\n");
+ if (check_clock_resolution_loops) {
+ int clock;
+ uint64_t diff;
+ int k;
+ struct timespec *now;
+ struct timespec prev;
+ struct timespec res;
+ int zero_diff = 0;
+ uint64_t min_non_zero_diff = UINT64_MAX;
+ uint64_t reported_resolution = UINT64_MAX;
+
+ now = calloc(check_clock_resolution_loops, sizeof(*now));
+ clock = clocksources[clocksel];
+
+ if (clock_getres(clock, &res)) {
+ warn("clock_getres failed");
+ } else {
+ reported_resolution = (NSEC_PER_SEC * res.tv_sec) + res.tv_nsec;
+ }
+
+ clock_gettime(clock, &prev);
+
+ for (k=0; k < check_clock_resolution_loops; k++) {
+ clock_gettime(clock, &now[k]);
+ }
+
+ if (verbose) {
+ printf("\n\nFor consecutive calls to clock_gettime():\n\n");
+ printf("time, delta time (nsec)\n\n");
+ }
+
+ prev = now[0];
+ for (k=1; k < check_clock_resolution_loops; k++) {
+
+ /* always show delta in ns */
+ diff = calcdiff_ns(now[k], prev);
+
+ if (diff == 0) {
+ zero_diff = 1;
+ } else if (diff < min_non_zero_diff) {
+ min_non_zero_diff = diff;
+ }
+
+ if (verbose) {
+ printf("%ld.%06ld", now[k].tv_sec, now[k].tv_nsec);
+ printf(" %llu\n", diff);
+ }
+
+ prev = now[k];
+ }
+
+ if (verbose ||
+ (min_non_zero_diff && (min_non_zero_diff > reported_resolution))) {
+ /*
+ * Measured clock resolution includes the time to call
+ * clock_gettime(), so it will be slightly larger than
+ * actual resolution.
+ */
+ fprintf(stderr, "reported clock resolution: %lld nsec\n",
+ reported_resolution);
+ fprintf(stderr, "measured clock resolution less than: %llu nsec\n",
+ min_non_zero_diff);
+ }
+
+ free(now);
+ }
+
mode = use_nanosleep + use_system;
sigemptyset(&sigset);
--
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