Module: xenomai-forge
Branch: next
Commit: 560327f8a0bc4d30ae6b89dedfd92f93f9adc111
URL:
http://git.xenomai.org/?p=xenomai-forge.git;a=commit;h=560327f8a0bc4d30ae6b89dedfd92f93f9adc111
Author: Philippe Gerum <r...@xenomai.org>
Date: Fri Aug 15 19:13:17 2014 +0200
utils/autotune: allow for changing the sampling period
---
doc/asciidoc/man1/autotune.adoc | 11 +++++++++++
utils/autotune/autotune.c | 21 +++++++++++++++++----
2 files changed, 28 insertions(+), 4 deletions(-)
diff --git a/doc/asciidoc/man1/autotune.adoc b/doc/asciidoc/man1/autotune.adoc
index 42d76bf..c099130 100644
--- a/doc/asciidoc/man1/autotune.adoc
+++ b/doc/asciidoc/man1/autotune.adoc
@@ -82,6 +82,17 @@ platform needs to deliver an IRQ to a user-space task/thread
running
in a Xenomai application process. This delay includes the context
switching time.
+**--period <ns>*::
+Set the sampling period to the given count of nanoseconds. The
+estimation is performed by measuring the jitter between the ideal time
+at which a timer tick should be received, and the actual time it is
+eventually received, for a series of ticks. This value expresses the
+delay between two of these ticks. If too short, a lockup might
+occur. A commonly observed result is: the larger the delay, the higher
+the latency, due to CPU cache effects (i.e. the real-time code/data is
+more likely to get evicted from the cachelines as the non real-time
+activity can slip in, treading over a larger address space).
+
*--reset*::
Reset the gravity values to their factory defaults. These defaults
are statically defined by the Xenomai platform code.
diff --git a/utils/autotune/autotune.c b/utils/autotune/autotune.c
index a36c606..3c019f3 100644
--- a/utils/autotune/autotune.c
+++ b/utils/autotune/autotune.c
@@ -75,6 +75,11 @@ static const struct option base_options[] = {
.val = 1
},
{
+#define period_opt 7
+ .name = "period",
+ .has_arg = 1,
+ },
+ {
.name = NULL,
}
};
@@ -179,11 +184,12 @@ static void usage(void)
fprintf(stderr, " --irq interrupt latency\n");
fprintf(stderr, " --kernel kernel scheduling latency\n");
fprintf(stderr, " --user user scheduling latency\n");
+ fprintf(stderr, " --period set the sampling period\n");
fprintf(stderr, " --reset reset core timer gravity to
factory defaults\n");
fprintf(stderr, " --nohog disable load generation\n");
fprintf(stderr, " --quiet tame down verbosity\n");
fprintf(stderr, " --help print this help\n\n");
- fprintf(stderr, "if no option is given, tune for all contexts\n");
+ fprintf(stderr, "if no option is given, tune for all contexts using the
default period.\n");
}
static void run_tuner(int fd, int op, int period, const char *type)
@@ -223,6 +229,8 @@ int main(int argc, char *const argv[])
int fd, period, ret, c, lindex, tuned = 0;
pthread_t hog;
+ period = CONFIG_XENO_DEFAULT_PERIOD;
+
for (;;) {
c = getopt_long_only(argc, argv, "", base_options, &lindex);
if (c == EOF)
@@ -238,6 +246,12 @@ int main(int argc, char *const argv[])
case help_opt:
usage();
exit(0);
+ case period_opt:
+ period = atoi(optarg);
+ if (period <= 0)
+ error(1, EINVAL, "invalid sampling period
(default %d)",
+ CONFIG_XENO_DEFAULT_PERIOD);
+ break;
case nohog_opt:
case quiet_opt:
break;
@@ -265,13 +279,12 @@ int main(int argc, char *const argv[])
error(1, errno, "reset failed");
}
- period = CONFIG_XENO_DEFAULT_PERIOD;
-
if (tune_irqlat || tune_kernlat || tune_userlat) {
if (!nohog)
create_hog(&hog);
if (!quiet)
- printf("Auto-tuning started (may take a while)\n");
+ printf("Auto-tuning started, period=%dns (may take a
while)\n",
+ period);
} else
nohog = 1;
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