Adding upstream version 1.6.4.upstream/1.6.4upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 281 insertions, 0 deletions

diff --git a/Documentation/libtracefs-synth2.txt b/Documentation/libtracefs-synth2.txt
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+libtracefs(3)
+=============
+
+NAME
+----
+tracefs_synth_create, tracefs_synth_destroy, tracefs_synth_complete,
+tracefs_synth_trace, tracefs_synth_snapshot, tracefs_synth_save
+- Creation of synthetic events
+
+SYNOPSIS
+--------
+[verse]
+--
+*#include <tracefs.h>*
+
+int *tracefs_synth_create*(struct tracefs_synth pass:[*]_synth_);
+int *tracefs_synth_destroy*(struct tracefs_synth pass:[*]_synth_);
+bool *tracefs_synth_complete*(struct tracefs_synth pass:[*]_synth_);
+
+int *tracefs_synth_trace*(struct tracefs_synth pass:[*]_synth_,
+			enum tracefs_synth_handler _type_, const char pass:[*]_var_);
+int *tracefs_synth_snapshot*(struct tracefs_synth pass:[*]_synth_,
+			   enum tracefs_synth_handler _type_, const char pass:[*]_var_);
+int *tracefs_synth_save*(struct tracefs_synth pass:[*]_synth_,
+		       enum tracefs_synth_handler _type_, const char pass:[*]_var_,
+		       char pass:[**]_save_fields_);
+--
+
+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. The synthetic events apply
+across all instances. A synthetic event must be created with *tracefs_synth_alloc*(3) before
+it can be created.
+
+*tracefs_synth_destroy*() destroys the synthetic event. It will attempt to stop the running of it in
+its instance (top by default), but if its running in another instance this may fail as busy.
+
+*tracefs_synth_complete*() returns true if the synthetic event _synth_ has both
+a starting and ending event.
+
+*tracefs_synth_trace*() Instead of doing just a trace on matching of the start and
+end events, do the _type_ handler where *TRACEFS_SYNTH_HANDLE_MAX* will do a trace
+when the given variable _var_ hits a new max for the matching keys. Or
+*TRACEFS_SYNTH_HANDLE_CHANGE* for when the _var_ changes. _var_ must be one of
+the _name_ elements used in *tracefs_synth_add_end_field*(3).
+
+*tracefs_synth_snapshot*() When the given variable _var_ is either a new max if
+_handler_ is *TRACEFS_SYNTH_HANDLE_MAX* or simply changed if *TRACEFS_SYNTH_HANDLE_CHANGE*
+then take a "snapshot" of the buffer. The snapshot moves the normal "trace" buffer
+into a "snapshot" buffer, that can be accessed via the "snapshot" file in the
+top level tracefs directory, or one of the instances.  _var_ changes. _var_ must be one of
+the _name_ elements used in *tracefs_synth_add_end_field*(3).
+
+*tracefs_synth_save*() When the given variable _var_ is either a new max if
+_handler_ is *TRACEFS_SYNTH_HANDLE_MAX* or simpy changed if *TRACEFS_SYNTH_HANDLE_CHANGE*
+then save the given _save_fields_ list. The fields will be stored in the histogram
+"hist" file of the event that can be retrieved with *tracefs_event_file_read*(3).
+_var_ must be one of the _name_ elements used in *tracefs_synth_add_end_field*(3).
+
+RETURN VALUE
+------------
+All functions return 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
+-------
+See *tracefs_sql*(3) for a more indepth use of some of this code.
+
+[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_alloc(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_echo_cmd() is run.
+	 */
+}
+
+/* Display how to create the synthetic event */
+static void show_event(void)
+{
+	struct trace_seq s;
+
+	trace_seq_init(&s);
+
+	tracefs_synth_echo_cmd(&s, 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(synth);
+		} else if (!strcmp(argv[1], "delete")) {
+			/* Delete the synthetic event */
+			tracefs_synth_destroy(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_alloc_2d*(3),
+*tracefs_hist_alloc_nd*(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),
+*tracefs_synth_alloc*(3),
+*tracefs_synth_add_match_field*(3),
+*tracefs_synth_add_compare_field*(3),
+*tracefs_synth_add_start_field*(3),
+*tracefs_synth_add_end_field*(3),
+*tracefs_synth_append_start_filter*(3),
+*tracefs_synth_append_end_filter*(3),
+*tracefs_synth_free*(3),
+*tracefs_synth_echo_cmd*(3),
+*tracefs_synth_get_start_hist*(3),
+*tracefs_synth_get_name*(3),
+*tracefs_synth_raw_fmt*(3),
+*tracefs_synth_show_event*(3),
+*tracefs_synth_show_start_hist*(3),
+*tracefs_synth_show_end_hist*(3),
+*tracefs_synth_get_event*(3),
+
+AUTHOR
+------
+[verse]
+--
+*Steven Rostedt* <rostedt@goodmis.org>
+*Tzvetomir Stoyanov* <tz.stoyanov@gmail.com>
+*sameeruddin shaik* <sameeruddin.shaik8@gmail.com>
+--
+REPORTING BUGS
+--------------
+Report bugs to  <linux-trace-devel@vger.kernel.org>
+
+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).