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NAME | SYNOPSIS | DESCRIPTION | KEY TYPES | RETURN VALUE | EXAMPLE | FILES | SEE ALSO | AUTHOR | REPORTING BUGS | LICENSE | RESOURCES | COPYING | NOTES | COLOPHON |
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LIBTRACEFS(3) libtracefs Manual LIBTRACEFS(3)
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
#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 *key;
enum tracefs_hist_key_type type;
};
struct tracefs_hist *tracefs_hist_alloc(struct tracefs_tep * tep,
const char *system, const char *event,
const char *key, enum tracefs_hist_key_type type);
struct tracefs_hist *tracefs_hist_alloc_2d(struct tracefs_tep * tep,
const char *system, const char *event,
const char *key1, enum tracefs_hist_key_type type1,
const char *key2, enum tracefs_hist_key_type type2));
struct tracefs_hist *tracefs_hist_alloc_nd(struct tracefs_tep * tep,
const char *system, const char *event,
struct tracefs_hist_axis *axes);
struct tracefs_hist *tracefs_hist_alloc_nd_cnt(struct tep_handle *tep,
const char *system, const char *event_name,
struct tracefs_hist_axis_cnt *axes);
void tracefs_hist_free(struct tracefs_hist *hist);
int tracefs_hist_add_key(struct tracefs_hist *hist, const char *key,
enum tracefs_hist_key_type type);
int tracefs_hist_add_key_cnt(struct tracefs_hist *hist, const char *key,
enum tracefs_hist_key_type type, int cnt);
int tracefs_hist_add_value(struct tracefs_hist *hist, const char *value);
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.
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.
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().
#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);
}
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.
libtracefs(3), libtraceevent(3), trace-cmd(1),
tracefs_hist_pause(3), tracefs_hist_continue(3),
tracefs_hist_reset(3)
Steven Rostedt <rostedt@goodmis.org[1]>
Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>
sameeruddin shaik <sameeruddin.shaik8@gmail.com[3]>
Report bugs to <linux-trace-devel@vger.kernel.org[4]>
libtracefs is Free Software licensed under the GNU LGPL 2.1
https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/
Copyright (C) 2020 VMware, Inc. Free use of this software is
granted under the terms of the GNU Public License (GPL).
1. rostedt@goodmis.org
mailto:rostedt@goodmis.org
2. tz.stoyanov@gmail.com
mailto:tz.stoyanov@gmail.com
3. sameeruddin.shaik8@gmail.com
mailto:sameeruddin.shaik8@gmail.com
4. linux-trace-devel@vger.kernel.org
mailto:linux-trace-devel@vger.kernel.org
This page is part of the libtracefs (Linux kernel trace file
system library) project. Information about the project can be
found at ⟨https://www.trace-cmd.org/⟩. If you have a bug report
for this manual page, see ⟨https://www.trace-cmd.org/⟩. This page
was obtained from the project's upstream Git repository
⟨https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git⟩ on
2025-02-02. (At that time, the date of the most recent commit
that was found in the repository was 2024-11-22.) If you discover
any rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page,
or you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a
mail to man-pages@man7.org
libtracefs 1.7.0 12/22/2023 LIBTRACEFS(3)
Pages that refer to this page: tracefs_filter_pid_function(3), tracefs_filter_string_append(3), tracefs_hist_start(3), tracefs_sql(3), tracefs_synth_alloc(3), tracefs_synth_create(3), tracefs_synth_echo_cmd(3)
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HTML rendering created 2025-02-02 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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