From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>
The man page for the synthetic event functions has more than 9, which
causes errors when creating them. Create a libtracefs-synth2.txt file and
move the descriptions of tracefs_synth_create(), tracefs_synth_destroy()
and tracefs_synth_show() to it.
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
Documentation/libtracefs-synth.txt | 31 +---
Documentation/libtracefs-synth2.txt | 239 ++++++++++++++++++++++++++++
2 files changed, 246 insertions(+), 24 deletions(-)
create mode 100644 Documentation/libtracefs-synth2.txt
diff --git a/Documentation/libtracefs-synth.txt b/Documentation/libtracefs-synth.txt
index 47e93bd42674..77076e1aa5e2 100644
--- a/Documentation/libtracefs-synth.txt
+++ b/Documentation/libtracefs-synth.txt
@@ -4,8 +4,8 @@ libtracefs(3)
NAME
----
tracefs_synth_init, tracefs_synth_add_match_field, tracefs_synth_add_compare_field, tracefs_synth_add_start_field,
-tracefs_synth_add_end_field, tracefs_synth_append_start_filter, tracefs_synth_append_end_filter, tracefs_synth_create,
-tracefs_synth_destroy, tracefs_synth_free, tracefs_synth_show - Creation of synthetic events
+tracefs_synth_add_end_field, tracefs_synth_append_start_filter, tracefs_synth_append_end_filter, tracefs_synth_free,
+- Creation of a synthetic event descriptor
SYNOPSIS
--------
@@ -47,14 +47,7 @@ int tracefs_synth_append_end_filter(struct tracefs_synth pass:[*]synth,
const char pass:[*]field,
enum tracefs_synth_compare compare,
const char pass:[*]val);
-int tracefs_synth_create(struct tracefs_instance pass:[*]instance,
- struct tracefs_synth pass:[*]synth);
-int tracefs_synth_destroy(struct tracefs_instance pass:[*]instance,
- struct tracefs_synth pass:[*]synth);
-void tracefs_synth_free(struct tracefs_synth pass:[*]synth);
-int tracefs_synth_show(struct trace_seq pass:[*]seq, struct tracefs_instance pass:[*]instance,
- struct tracefs_synth pass:[*]synth);
-
+-void tracefs_synth_free(struct tracefs_synth pass:[*]synth);
--
DESCRIPTION
@@ -78,7 +71,7 @@ delta in microseconds. This is used as the example below.
*tracefs_synth_init*() allocates and initializes a synthetic event.
It does not create the synthetic event, but supplies the minimal information
-to do so. See *tracefs_synth_create*() below for how to create the synthetic
+to do so. See *tracefs_synth_create*(3) for how to create the synthetic
event in the system. It requires a _tep_ handler that can be created by
*tracefs_local_events*(3) for more information. The _name_ holds the name
of the synthetic event that will be created. The _start_system is the name
@@ -162,22 +155,9 @@ _field_, _compare_, and _val_ are ignored unless _type_ is equal to
*tracefs_synth_append_end_filter*() is the same as *tracefs_synth_append_start_filter* but
filters on the ending event.
-*tracefs_synth_create*() creates the synthetic event in the system in the system
-in the _instance_ provided. Note, synthetic events apply across all instances,
-but some creation requires histograms to be established, which are local to
-instances.
-
-*tracefs_synth_destroy*() destroys the synthetic event. It will attempt to stop
-the running of it in the given _instance_, but if its running in another instance
-this may fail as busy.
-
*tracefs_synth_free*() frees the allocated descriptor returned by
*tracefs_synth_init*().
-*tracefs_synth_show*() acts like *tracefs_synth_create*(), but instead of creating
-the synthetic event in the given _instance_, it will write the echo commands to
-manually create it in the _seq_ given.
-
RETURN VALUE
------------
*tracefs_synth_init*() returns an allocated struct tracefs_synth descriptor
@@ -330,6 +310,9 @@ FILES
SEE ALSO
--------
+_tracefs_synth_create_(3),
+_tracefs_synth_destroy_(3),
+_tracfes_synth_show_(3),
_libtracefs(3)_,
_libtraceevent(3)_,
_trace-cmd(1)_,
diff --git a/Documentation/libtracefs-synth2.txt b/Documentation/libtracefs-synth2.txt
new file mode 100644
index 000000000000..41680d5b9cba
--- /dev/null
+++ b/Documentation/libtracefs-synth2.txt
@@ -0,0 +1,239 @@
+libtracefs(3)
+=============
+
+NAME
+----
+tracefs_synth_create, tracefs_synth_destroy, tracefs_synth_show - Creation of synthetic events
+
+SYNOPSIS
+--------
+[verse]
+--
+*#include <tracefs.h>*
+
+int tracefs_synth_create(struct tracefs_instance pass:[*]instance,
+ struct tracefs_synth pass:[*]synth);
+int tracefs_synth_destroy(struct tracefs_instance pass:[*]instance,
+ struct tracefs_synth pass:[*]synth);
+int tracefs_synth_show(struct trace_seq pass:[*]seq, struct tracefs_instance pass:[*]instance,
+ struct tracefs_synth pass:[*]synth);
+
+--
+
+DESCRIPTION
+-----------
+Synthetic events are dynamic events that are created by matching
+two other events which triggers a synthetic event. One event is the starting
+event which some field is recorded, and when the second event is executed,
+if it has a field (or fields) that matches the starting event's field (or fields)
+then it will trigger the synthetic event. The field values other than the matching
+fields may be passed from the starting event to the end event to perform calculations
+on, or to simply pass as a parameter to the synthetic event.
+
+One common use case is to set "sched_waking" as the starting event. This event is
+triggered when a process is awoken. Then set "sched_switch" as the ending event.
+This event is triggered when a new task is scheduled on the CPU. By setting
+the "common_pid" of both events as the matching fields, the time between the
+two events is considered the wake up latency of that process. Use *TRACEFS_TIMESTAMP*
+as a field for both events to calculate the delta in nanoseconds, or use
+*TRACEFS_TIMESTAMP_USECS" as the compare fields for both events to calculate the
+delta in microseconds. This is used as the example below.
+
+*tracefs_synth_create*() creates the synthetic event in the system in the system
+in the _instance_ provided. Note, synthetic events apply across all instances,
+but some creation requires histograms to be established, which are local to
+instances.
+
+*tracefs_synth_destroy*() destroys the synthetic event. It will attempt to stop
+the running of it in the given _instance_, but if its running in another instance
+this may fail as busy.
+
+*tracefs_synth_show*() acts like *tracefs_synth_create*(), but instead of creating
+the synthetic event in the given _instance_, it will write the echo commands to
+manually create it in the _seq_ given.
+
+RETURN VALUE
+------------
+Returns zero on success or -1 on error.
+
+ERRORS
+------
+The following errors are for all the above calls:
+
+*EPERM* Not run as root user when required.
+
+*EINVAL* Either a parameter is not valid (NULL when it should not be)
+ or a field that is not compatible for calculations.
+
+*ENODEV* An event or one of its fields is not found.
+
+*EBADE* The fields of the start and end events are not compatible for
+ either matching or comparing.
+
+*ENOMEM* not enough memory is available.
+
+And more errors may have happened from the system calls to the system.
+
+EXAMPLE
+-------
+[source,c]
+--
+#include <stdlib.h>
+#include <tracefs.h>
+
+#define start_event "sched_waking"
+#define start_field "pid"
+
+#define end_event "sched_switch"
+#define end_field "next_pid"
+
+#define match_name "pid"
+
+static struct tracefs_synth *synth;
+
+static void make_event(void)
+{
+ struct tep_handle *tep;
+
+ /* Load all events from the system */
+ tep = tracefs_local_events(NULL);
+
+ /* Initialize the synthetic event */
+ synth = tracefs_synth_init(tep, "wakeup_lat",
+ NULL, start_event,
+ NULL, end_event,
+ start_field, end_field,
+ match_name);
+
+ /* The tep is no longer needed */
+ tep_free(tep);
+
+
+ /* Save the "prio" field as "prio" from the start event */
+ tracefs_synth_add_start_field(synth, "prio", NULL);
+
+ /* Save the "next_comm" as "comm" from the end event */
+ tracefs_synth_add_end_field(synth, "next_comm", "comm");
+
+ /* Save the "prev_prio" as "prev_prio" from the end event */
+ tracefs_synth_add_end_field(synth, "prev_prio", NULL);
+
+ /*
+ * Take a microsecond time difference between end and start
+ * and record as "delta"
+ */
+ tracefs_synth_add_compare_field(synth, TRACEFS_TIMESTAMP_USECS,
+ TRACEFS_TIMESTAMP_USECS,
+ TRACEFS_SYNTH_DELTA_END, "delta");
+
+ /* Only record if start event "prio" is less than 100 */
+ tracefs_synth_append_start_filter(synth, TRACEFS_FILTER_COMPARE,
+ "prio", TRACEFS_COMPARE_LT, "100");
+
+ /*
+ * Only record if end event "next_prio" is less than 50
+ * or the previous task's prio was not greater than or equal to 100.
+ * next_prio < 50 || !(prev_prio >= 100)
+ */
+ tracefs_synth_append_end_filter(synth, TRACEFS_FILTER_COMPARE,
+ "next_prio", TRACEFS_COMPARE_LT, "50");
+ tracefs_synth_append_end_filter(synth, TRACEFS_FILTER_OR, NULL, 0, NULL);
+ tracefs_synth_append_end_filter(synth, TRACEFS_FILTER_NOT, NULL, 0, NULL);
+ tracefs_synth_append_end_filter(synth, TRACEFS_FILTER_OPEN_PAREN, NULL, 0, NULL);
+ tracefs_synth_append_end_filter(synth, TRACEFS_FILTER_COMPARE,
+ "prev_prio", TRACEFS_COMPARE_GE, "100");
+ /*
+ * Note, the above only added: "next_prio < 50 || !(prev_prio >= 100"
+ * That's because, when the synth is executed, the remaining close parenthesis
+ * will be added. That is, the string will end up being:
+ * "next_prio < 50 || !(prev_prio >= 100)" when one of tracefs_sync_create()
+ * or tracefs_sync_show() is run.
+ */
+}
+
+/* Display how to create the synthetic event */
+static void show_event(void)
+{
+ struct trace_seq s;
+
+ trace_seq_init(&s);
+
+ tracefs_synth_show(&s, NULL, synth);
+ trace_seq_terminate(&s);
+ trace_seq_do_printf(&s);
+ trace_seq_destroy(&s);
+}
+
+int main (int argc, char **argv)
+{
+ make_event();
+
+ if (argc > 1) {
+ if (!strcmp(argv[1], "create")) {
+ /* Create the synthetic event */
+ tracefs_synth_create(NULL, synth);
+ } else if (!strcmp(argv[1], "delete")) {
+ /* Delete the synthetic event */
+ tracefs_synth_destroy(NULL, synth);
+ } else {
+ printf("usage: %s [create|delete]\n", argv[0]);
+ exit(-1);
+ }
+ } else
+ show_event();
+
+ tracefs_synth_free(synth);
+
+ return 0;
+}
+--
+
+FILES
+-----
+[verse]
+--
+*tracefs.h*
+ Header file to include in order to have access to the library APIs.
+*-ltracefs*
+ Linker switch to add when building a program that uses the library.
+--
+
+SEE ALSO
+--------
+_libtracefs(3)_,
+_libtraceevent(3)_,
+_trace-cmd(1)_,
+_tracefs_hist_alloc(3)_,
+_tracefs_hist_free(3)_,
+_tracefs_hist_add_key(3)_,
+_tracefs_hist_add_value(3)_,
+_tracefs_hist_add_name(3)_,
+_tracefs_hist_start(3)_,
+_tracefs_hist_destory(3)_,
+_tracefs_hist_add_sort_key(3)_,
+_tracefs_hist_sort_key_direction(3)_
+
+AUTHOR
+------
+[verse]
+--
+*Steven Rostedt* <rostedt@xxxxxxxxxxx>
+*Tzvetomir Stoyanov* <tz.stoyanov@xxxxxxxxx>
+*sameeruddin shaik* <sameeruddin.shaik8@xxxxxxxxx>
+--
+REPORTING BUGS
+--------------
+Report bugs to <linux-trace-devel@xxxxxxxxxxxxxxx>
+
+LICENSE
+-------
+libtracefs is Free Software licensed under the GNU LGPL 2.1
+
+RESOURCES
+---------
+https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/
+
+COPYING
+-------
+Copyright \(C) 2020 VMware, Inc. Free use of this software is granted under
+the terms of the GNU Public License (GPL).
--
2.30.2
|