path: root/Documentation/libtracefs-hist.txt

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

NAME
----
tracefs_hist_alloc, tracefs_hist_alloc_2d, tracefs_hist_alloc_nd, tracefs_hist_alloc_nd_cnt, tracefs_hist_free,
tracefs_hist_add_key, tracefs_hist_add_key_cnt, tracefs_hist_add_value - Create and destroy event histograms

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

enum *tracefs_hist_key_type* {
	*TRACEFS_HIST_KEY_NORMAL* = 0,
	*TRACEFS_HIST_KEY_HEX*,
	*TRACEFS_HIST_KEY_SYM*,
	*TRACEFS_HIST_KEY_SYM_OFFSET*,
	*TRACEFS_HIST_KEY_SYSCALL*,
	*TRACEFS_HIST_KEY_EXECNAME*,
	*TRACEFS_HIST_KEY_LOG*,
	*TRACEFS_HIST_KEY_USECS*,
	*TRACEFS_HIST_KEY_MAX*
};

struct *tracefs_hist_axis* {
	const char pass:[*]_key_;
	enum tracefs_hist_key_type _type_;
};

struct tracefs_hist pass:[*]*tracefs_hist_alloc*(struct tracefs_tep pass:[*] _tep_,
			const char pass:[*]_system_, const char pass:[*]_event_,
			const char pass:[*]_key_, enum tracefs_hist_key_type _type_);
struct tracefs_hist pass:[*]*tracefs_hist_alloc_2d*(struct tracefs_tep pass:[*] _tep_,
			const char pass:[*]_system_, const char pass:[*]_event_,
			const char pass:[*]_key1_, enum tracefs_hist_key_type _type1_,
			const char pass:[*]_key2_, enum tracefs_hist_key_type _type2_));
struct tracefs_hist pass:[*]*tracefs_hist_alloc_nd*(struct tracefs_tep pass:[*] _tep_,
			const char pass:[*]_system_, const char pass:[*]_event_,
			struct tracefs_hist_axis pass:[*]_axes_);
struct tracefs_hist pass:[*]*tracefs_hist_alloc_nd_cnt*(struct tep_handle pass:[*]_tep_,
			  const char pass:[*]_system_, const char pass:[*]_event_name_,
			  struct tracefs_hist_axis_cnt pass:[*]_axes_);
void *tracefs_hist_free*(struct tracefs_hist pass:[*]_hist_);

int *tracefs_hist_add_key*(struct tracefs_hist pass:[*]_hist_, const char pass:[*]_key_,
			 enum tracefs_hist_key_type _type_);
int *tracefs_hist_add_key_cnt*(struct tracefs_hist pass:[*]_hist_, const char pass:[*]_key_,
			 enum tracefs_hist_key_type _type_, int _cnt_);
int *tracefs_hist_add_value*(struct tracefs_hist pass:[*]_hist_, const char pass:[*]_value_);
--

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_alloc*() allocates a "struct tracefs_hist" descriptor of a one-dimensional
histogram and returns the address of it. This descriptor must be freed by *tracefs_hist_free*().
The _tep_ is a trace event handle (see *tracefs_local_events*(3)), that holds the
_system_ and _event_ that the histogram will be attached to. The _system_ is the
system or group of the event. The _event_ is the event to attach the histogram to.
The _key_ is a field of the event that will be used as the key(dimension) of the histogram.
The _type_ is the type of the _key_. See KEY TYPES below.

*tracefs_hist_alloc_2d*() allocates a "struct tracefs_hist" descriptor of a two-dimensional
histogram and returns the address of it. This descriptor must be freed by *tracefs_hist_free*().
The _tep_ is a trace event handle (see *tracefs_local_events*(3)), that holds the
_system_ and _event_ that the histogram will be attached to. The _system_ is the
system or group of the event. The _event_ is the event to attach the histogram to.
The _key1_ is the first field of the event that will be used as the key(dimension)
of the histogram. The _type1_ is the type of the _key1_. See KEY TYPES below.
The _key2_ is the second field of the event that will be used as the key(dimension)
of the histogram. The _type2_ is the type of the _key2_. See KEY TYPES below.

*tracefs_hist_alloc_nd*() allocates a "struct tracefs_hist" descriptor of an N-dimensional
histogram and returns the address of it. This descriptor must be freed by *tracefs_hist_free*().
The _tep_ is a trace event handle (see *tracefs_local_events*(3)), that holds the
_system_ and _event_ that the histogram will be attached to. The _system_ is the
system or group of the event. The _event_ is the event to attach the histogram to.
The _axes_ is an array of _key_ / _type_ pairs, defining the dimensions of the histogram.

*tracefs_hist_alloc_nd_cnt*() will initialize a histogram descriptor that will be attached to
the _system_/_event_. This only initializes the descriptor with the given _axes_ keys as primaries.
This only initializes the descriptor, it does not start the histogram in the kernel.
The difference between this and *tracefs_hist_alloc_nd()* is that the _axes_ parameter
is of type *struct tracefs_hist_axis_cnt* and not *struct tracefs_hist_axis*.

*tracefs_hist_free*() frees the _tracefs_hist_ descriptor. Note, it does not stop
or disable the running histogram if it was started. *tracefs_hist_destroy*() needs
to be called to do so.

*tracefs_hist_add_key*() Adds a secondary or tertiary key to the histogram.
The key passed to *tracefs_hist_alloc_nd*() is the primary key of the histogram.
The first time this function is called, it will add a secondary key (or two dimensional
histogram). If this function is called again on the same histogram, it will add
a _tertiary_ key (or three dimensional histogram). The _hist_ parameter is the
histogram descriptor to add the _key_ to. The _type_ is the type of key to add
(See KEY TYPES below).

The *tracefs_hist_add_key_cnt*() is the same as *tracefs_hist_add_key*() except
that it allows to add a counter for the given type. Currently, there's only
the *buckets* type that requires a counter. When adding a key with the buckets
type, *tracefs_hist_add_key*() is not sufficient, as the *buckets* type requires
a counter or bucket size. Use *tracefs_hist_add_key_cnt*() when specifing
a key that is broken up into  buckets, and pass in the size of those buckets
into _cnt_.

*tracefs_hist_add_value*() will add a value to record. By default, the value is
simply the "hitcount" of the number of times a instance of the histogram's
key was hit. The _hist_ is the histogram descriptor to add the value to.
The _value_ is a field in the histogram to add to when an instance of the
key is hit.

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

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

If *tracefs_hist_start*() returns an error, a message may be displayed
in the kernel that can be retrieved by *tracefs_error_last()*.

EXAMPLE
-------
[source,c]
--
#include <stdlib.h>
#include <ctype.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_cnt **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_cnt *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 if (strncmp(att, "buckets", 7) == 0) {
				if (att[7] != '=' && !isdigit(att[8])) {
					fprintf(stderr, "'buckets' key type requires '=<size>'\n");
					exit(-1);
				}
				ax[cnt].type = TRACEFS_HIST_KEY_BUCKETS;
				ax[cnt].cnt = atoi(&att[8]);
			} 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_cnt *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);
	}

	/* buckets require the nd_cnt function */
	switch (cnt) {
	case 2:
		if (axes[1].type == TRACEFS_HIST_KEY_BUCKETS)
			cnt = -1;
		/* fall through */
	case 1:
		if (axes[0].type == TRACEFS_HIST_KEY_BUCKETS)
			cnt = -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_cnt(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).