libtracefs(3)
=============

NAME
----
tracefs_hist_add_sort_key, tracefs_hist_set_sort_key, tracefs_hist_sort_key_direction,
tracefs_hist_add_name, tracefs_hist_append_filter, tracefs_hist_echo_cmd, tracefs_hist_command,
tracefs_hist_get_name, tracefs_hist_get_event, tracefs_hist_get_system - Update and describe an event histogram

SYNOPSIS
--------
[verse]
--
*#include <tracefs.h>*

int *tracefs_hist_add_sort_key*(struct tracefs_hist pass:[*]_hist_,
			      const char pass:[*]_sort_key_);

int *tracefs_hist_set_sort_key*(struct tracefs_hist pass:[*]_hist_,
			      const char pass:[*]_sort_key_, _..._);
int *tracefs_hist_sort_key_direction*(struct tracefs_hist pass:[*]_hist_,
				    const char pass:[*]_sort_key_,
				    enum tracefs_hist_sort_direction _dir_);

int *tracefs_hist_add_name*(struct tracefs_hist pass:[*]_hist_, const char pass:[*]_name_);

int *tracefs_hist_append_filter*(struct tracefs_hist pass:[*]_hist_,
			       enum tracefs_filter _type_,
			       const char pass:[*]_field_,
			       enum tracefs_compare _compare_,
			       const char pass:[*]_val_);

int *tracefs_hist_echo_cmd*(struct trace_seq pass:[*]_s_, struct tracefs_instance pass:[*]_instance_,
			  struct tracefs_hist pass:[*]_hist_,
			  enum tracefs_hist_command _command_);

int *tracefs_hist_command*(struct tracefs_instance pass:[*]_instance_,
			 struct tracefs_hist pass:[*]_hist_,
			 enum tracefs_hist_command _command_);

const char pass:[*]*tracefs_hist_get_name*(struct tracefs_hist pass:[*]_hist_);

const char pass:[*]*tracefs_hist_get_event*(struct tracefs_hist pass:[*]_hist_);

const char pass:[*]*tracefs_hist_get_system*(struct tracefs_hist pass:[*]_hist_);

--

DESCRIPTION
-----------
Event histograms are created by the trigger file in the event directory.
The syntax can be complex and difficult to get correct. This API handles the
syntax, and facilitates the creation and interaction with the event histograms.
See https://www.kernel.org/doc/html/latest/trace/histogram.html for more information.

*tracefs_hist_add_sort_key*() will add a key to sort on. The _hist_ is the
histogram descriptor to add the sort key to. The _sort_key_ is a string
that must match either an already defined key of the histogram, or an already
defined value. If _hist_  already has sorting keys (previously added) the new
_sort_key_ will have lower priority(be secondary or so on) when sorting.

*tracefs_hist_set_sort_key*() will reset the list of key to sort on. The _hist_ is
the histogram descriptor to reset the sort key to. The _sort_key_ is a string
that must match either an already defined key of the histogram, or an already
defined value. Multiple sort keys may be added to denote a secondary, sort order
and so on, but all sort keys must match an existing key or value, or be
TRACEFS_HIST_HITCOUNT. The last parameter of *tracefs_hist_add_sort_key*() must
be NULL.

*tracefs_hist_sort_key_direction*() allows to change the direction of an
existing sort key of _hist_. The _sort_key_ is the sort key to change, and
_dir_ can be either TRACEFS_HIST_SORT_ASCENDING or TRACEFS_HIST_SORT_DESCENDING,
to make the direction of the sort key either ascending or descending respectively.

*tracefs_hist_add_name*() adds a name to a histogram. A histogram may be
named and if the name matches between more than one event, and they have
compatible keys, the multiple histograms with the same name will be merged
into a single histogram (shown by either event's hist file). The _hist_
is the histogram to name, and the _name_ is the name to give it.

*tracefs_hist_append_filter*() creates a filter or appends to it for the
histogram  event. Depending on _type_, it will build a string of tokens for
parenthesis or logic statements, or it may add a comparison of _field_
to _val_ based on _compare_.

If _type_ is:
*TRACEFS_FILTER_COMPARE*     -  See below
*TRACEFS_FILTER_AND*         -  Append "&&" to the filter
*TRACEFS_FILTER_OR*          -  Append "||" to the filter
*TRACEFS_FILTER_NOT*         -  Append "!" to the filter
*TRACEFS_FILTER_OPEN_PAREN*  -  Append "(" to the filter
*TRACEFS_FILTER_CLOSE_PAREN* -  Append ")" to the filter

_field_, _compare_, and _val_ are ignored unless _type_ is equal to
*TRACEFS_FILTER_COMPARE*, then _compare_ will be used for the following:

*TRACEFS_COMPARE_EQ* - _field_ == _val_

*TRACEFS_COMPARE_NE* - _field_ != _val_

*TRACEFS_COMPARE_GT* - _field_ > _val_

*TRACEFS_COMPARE_GE* - _field_ >= _val_

*TRACEFS_COMPARE_LT* - _field_ < _val_

*TRACEFS_COMPARE_LE* - _field_ <pass:[=] _val_

*TRACEFS_COMPARE_RE* - _field_ ~ "_val_" : where _field_ is a string.

*TRACEFS_COMPARE_AND* - _field_ & _val_ : where _field_ is a flags field.

*trace_hist_echo_cmd*() prints the commands needed to create the given histogram
in the given _instance_, or NULL for the top level, into the _seq_.
The command that is printed is described by _command_ and shows the functionality
that would be done by *tracefs_hist_command*(3).

*tracefs_hist_command*() is called to process a command on the histogram
_hist_ for its event in the given _instance_, or NULL for the top level.
The _cmd_ can be one of:

*TRACEFS_HIST_CMD_START* or zero to start execution of the histogram.

*TRACEFS_HIST_CMD_PAUSE* to pause the given histogram.

*TRACEFS_HIST_CMD_CONT* to continue a paused histogram.

*TRACEFS_HIST_CMD_CLEAR* to reset the values of a histogram.

*TRACEFS_HIST_CMD_DESTROY* to destroy the histogram (undo a START).

The below functions are wrappers to tracefs_hist_command() to make the
calling conventions a bit easier to understand what is happening.

KEY TYPES
---------

*tracefs_hist_alloc_nd*() and *tracefs_hist_add_key*() both add a key and requires
that key to have a type. The types may be:

*TRACEFS_HIST_KEY_NORMAL* or zero (0) which is to not modify the type.

*TRACEFS_HIST_KEY_HEX* to display the key in hex.

*TRACEFS_HIST_KEY_SYM* to display the key as a kernel symbol (if found). If
the key is an address, this is useful as it will display the function names instead
of just a number.

*TRACEFS_HIST_KEY_SYM_OFFSET* similar to *TRACEFS_HIST_KEY_SYM* but will also include
the offset of the function to match the exact address.

*TRACEFS_HIST_KEY_SYSCALL* If the key is a system call "id" (the number passed from user
space to the kernel to tell it what system call it is calling), then the name of
the system call is displayed.

*TRACEFS_HIST_KEY_EXECNAME* If "common_pid" is the key (the pid of the executing task),
instead of showing the number, show the name of the running task.

*TRACEFS_HIST_KEY_LOG* will display the key in a binary logarithmic scale.

*TRACEFS_HIST_KEY_USECS* for use with "common_timestamp" or TRACEFS_HIST_TIMESTAMP,
in which case it will show the timestamp in microseconds instead of nanoseconds.

RETURN VALUE
------------
*tracefs_hist_get_name*() returns the name of the histogram or NULL on error.
The returned string belongs to the histogram object and is freed with the histogram
by *tracefs_hist_free*().

*tracefs_hist_get_event*() returns the event name of the histogram or NULL on error.
The returned string belongs to the histogram object and is freed with the histogram
by *tracefs_hist_free*().

*tracefs_hist_get_system*() returns the system name of the histogram or NULL on error.
The returned string belongs to the histogram object and is freed with the histogram
by *tracefs_hist_free*().

*tracefs_hist_alloc_nd*() returns an allocated histogram descriptor which must
be freed by *tracefs_hist_free*() or NULL on error.

*tracefs_hist_get_name*(), *tracefs_hist_get_event*() and *tracefs_hist_get_system*()
return strings owned by the histogram object.

All the other functions return zero on success or -1 on error.

EXAMPLE
-------
[source,c]
--
#include <stdlib.h>
#include <unistd.h>
#include <tracefs.h>

enum commands {
	START,
	PAUSE,
	CONT,
	RESET,
	DELETE,
	SHOW,
};

static void parse_system_event(char *group, char **system, char **event)
{
	*system = strtok(group, "/");
	*event = strtok(NULL, "/");
	if (!*event) {
		*event = *system;
		*system = NULL;
	}
}

static int parse_keys(char *keys, struct tracefs_hist_axis **axes)
{
	char *sav = NULL;
	char *key;
	int cnt = 0;

	for (key = strtok_r(keys, ",", &sav); key; key = strtok_r(NULL, ",", &sav)) {
		struct tracefs_hist_axis *ax;
		char *att;

		ax = realloc(*axes, sizeof(*ax) * (cnt + 2));
		if (!ax) {
			perror("Failed to allocate axes");
			exit(-1);
		}
		ax[cnt].key = key;
		ax[cnt].type = 0;
		ax[cnt + 1].key = NULL;
		ax[cnt + 1].type = 0;

		*axes = ax;

		att = strchr(key, '.');
		if (att) {
			*att++ = '\0';
			if (strcmp(att, "hex") == 0)
				ax[cnt].type = TRACEFS_HIST_KEY_HEX;
			else if (strcmp(att, "sym") == 0)
				ax[cnt].type = TRACEFS_HIST_KEY_SYM;
			else if (strcmp(att, "sym_offset") == 0)
				ax[cnt].type = TRACEFS_HIST_KEY_SYM_OFFSET;
			else if (strcmp(att, "syscall") == 0)
				ax[cnt].type = TRACEFS_HIST_KEY_SYSCALL;
			else if (strcmp(att, "exec") == 0)
				ax[cnt].type = TRACEFS_HIST_KEY_EXECNAME;
			else if (strcmp(att, "log") == 0)
				ax[cnt].type = TRACEFS_HIST_KEY_LOG;
			else if (strcmp(att, "usecs") == 0)
				ax[cnt].type = TRACEFS_HIST_KEY_USECS;
			else {
				fprintf(stderr, "Undefined attribute '%s'\n", att);
				fprintf(stderr,"  Acceptable attributes:\n");
				fprintf(stderr,"    hex, sym, sym_offset, syscall, exe, log, usecs\n");
				exit(-1);
			}
		}
		cnt++;
	}
	return cnt;
}

static void process_hist(enum commands cmd, const char *instance_name,
			 char *group, char *keys, char *vals, char *sort,
			 char *ascend, char *desc)
{
	struct tracefs_instance *instance = NULL;
	struct tracefs_hist *hist;
	struct tep_handle *tep;
	struct tracefs_hist_axis *axes = NULL;
	char *system;
	char *event;
	char *sav;
	char *val;
	int ret;
	int cnt;

	if (instance_name) {
		instance = tracefs_instance_create(instance_name);
		if (!instance) {
			fprintf(stderr, "Failed instance create\n");
			exit(-1);
		}
	}

	tep = tracefs_local_events(NULL);
	if (!tep) {
		perror("Could not read events");
		exit(-1);
	}

	parse_system_event(group, &system, &event);

	if (cmd == SHOW) {
		char *content;
		content = tracefs_event_file_read(instance, system, event,
						  "hist", NULL);
		if (!content) {
			perror("Reading hist file");
			exit(-1);
		}
		printf("%s\n", content);
		free(content);
		return;
	}

	if (!keys) {
		fprintf(stderr, "Command needs -k option\n");
		exit(-1);
	}

	cnt = parse_keys(keys, &axes);
	if (!cnt) {
		fprintf(stderr, "No keys??\n");
		exit(-1);
	}

	/* Show examples of hist1d and hist2d */
	switch (cnt) {
	case 1:
		hist = tracefs_hist_alloc(tep, system, event,
					  axes[0].key, axes[0].type);
		break;
	case 2:
		hist = tracefs_hist_alloc_2d(tep, system, event,
					     axes[0].key, axes[0].type,
					     axes[1].key, axes[1].type);
		break;
	default:
		/* Really, 1 and 2 could use this too */
		hist = tracefs_hist_alloc_nd(tep, system, event, axes);
	}
	if (!hist) {
		fprintf(stderr, "Failed hist create\n");
		exit(-1);
	}

	if (vals) {
		sav = NULL;
		for (val = strtok_r(vals, ",", &sav); val; val = strtok_r(NULL, ",", &sav)) {
			ret = tracefs_hist_add_value(hist, val);
			if (ret) {
				fprintf(stderr, "Failed to add value %s\n", val);
				exit(-1);
			}
		}
	}

	if (sort) {
		sav = NULL;
		for (val = strtok_r(sort, ",", &sav); val; val = strtok_r(NULL, ",", &sav)) {
			ret = tracefs_hist_add_sort_key(hist, val);
			if (ret) {
				fprintf(stderr, "Failed to add sort key/val %s\n", val);
				exit(-1);
			}
		}
	}

	if (ascend) {
		sav = NULL;
		for (val = strtok_r(ascend, ",", &sav); val; val = strtok_r(NULL, ",", &sav)) {
			ret = tracefs_hist_sort_key_direction(hist, val, TRACEFS_HIST_SORT_ASCENDING);
			if (ret) {
				fprintf(stderr, "Failed to add ascending key/val %s\n", val);
				exit(-1);
			}
		}
	}

	if (desc) {
		sav = NULL;
		for (val = strtok_r(desc, ",", &sav); val; val = strtok_r(NULL, ",", &sav)) {
			ret = tracefs_hist_sort_key_direction(hist, val, TRACEFS_HIST_SORT_DESCENDING);
			if (ret) {
				fprintf(stderr, "Failed to add descending key/val %s\n", val);
				exit(-1);
			}
		}
	}

	tracefs_error_clear(instance);

	switch (cmd) {
	case START:
		ret = tracefs_hist_start(instance, hist);
		if (ret) {
			char *err = tracefs_error_last(instance);
			if (err)
				fprintf(stderr, "\n%s\n", err);
		}
		break;
	case PAUSE:
		ret = tracefs_hist_pause(instance, hist);
		break;
	case CONT:
		ret = tracefs_hist_continue(instance, hist);
		break;
	case RESET:
		ret = tracefs_hist_reset(instance, hist);
		break;
	case DELETE:
		ret = tracefs_hist_destroy(instance, hist);
		break;
	case SHOW:
		/* Show was already done */
		break;
	}
	if (ret)
		fprintf(stderr, "Failed: command\n");
	exit(ret);
}

int main (int argc, char **argv, char **env)
{
	enum commands cmd;
	char *instance = NULL;
	char *cmd_str;
	char *event = NULL;
	char *keys = NULL;
	char *vals = NULL;
	char *sort = NULL;
	char *desc = NULL;
	char *ascend = NULL;

	if (argc < 2) {
		fprintf(stderr, "usage: %s command [-B instance][-e [system/]event][-k keys][-v vals][-s sort]\n", argv[0]);
		fprintf(stderr, "      [-a ascending][-d descending]\n");
		exit(-1);
	}

	cmd_str = argv[1];

	if (!strcmp(cmd_str, "start"))
		cmd = START;
	else if (!strcmp(cmd_str, "pause"))
		cmd = PAUSE;
	else if (!strcmp(cmd_str, "cont"))
		cmd = CONT;
	else if (!strcmp(cmd_str, "reset"))
		cmd = RESET;
	else if (!strcmp(cmd_str, "delete"))
		cmd = DELETE;
	else if (!strcmp(cmd_str, "show"))
		cmd = SHOW;
	else {
		fprintf(stderr, "Unknown command %s\n", cmd_str);
		exit(-1);
	}

	for (;;) {
		int c;

		c = getopt(argc - 1, argv + 1, "e:k:v:B:s:d:a:");
		if (c == -1)
			break;

		switch (c) {
		case 'e':
			event = optarg;
			break;
		case 'k':
			keys = optarg;
			break;
		case 'v':
			vals = optarg;
			break;
		case 'B':
			instance = optarg;
			break;
		case 's':
			sort = optarg;
			break;
		case 'd':
			desc = optarg;
			break;
		case 'a':
			ascend = optarg;
			break;
		}
	}
	if (!event) {
		event = "kmem/kmalloc";
		if (!keys)
			keys = "call_site.sym,bytes_req";
		if (!vals)
			vals = "bytes_alloc";
		if (!sort)
			sort = "bytes_req,bytes_alloc";
		if (!desc)
			desc = "bytes_alloc";
	}
	process_hist(cmd, instance, event, keys, vals, sort, ascend, desc);
}
--

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_pause*(3),
*tracefs_hist_continue*(3),
*tracefs_hist_reset*(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).