tracefs_hist_alloc(3) — Linux manual page

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LIBTRACEFS(3)               libtracefs Manual              LIBTRACEFS(3)

NAME         top

       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         top

       #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);

DESCRIPTION         top

       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         top

       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         top

       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         top

           #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         top

           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         top

       libtracefs(3), libtraceevent(3), trace-cmd(1),
       tracefs_hist_pause(3), tracefs_hist_continue(3),
       tracefs_hist_reset(3)

AUTHOR         top

           Steven Rostedt <rostedt@goodmis.org[1]>
           Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>
           sameeruddin shaik <sameeruddin.shaik8@gmail.com[3]>

REPORTING BUGS         top

       Report bugs to <linux-trace-devel@vger.kernel.org[4]>

LICENSE         top

       libtracefs is Free Software licensed under the GNU LGPL 2.1

RESOURCES         top

       https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/ 

COPYING         top

       Copyright (C) 2020 VMware, Inc. Free use of this software is
       granted under the terms of the GNU Public License (GPL).

NOTES         top

        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

COLOPHON         top

       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
       2024-06-14.  (At that time, the date of the most recent commit
       that was found in the repository was 2024-05-17.)  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)

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