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NAME |SYNOPSIS |DESCRIPTION |KEY TYPES |RETURN VALUE |EXAMPLE |FILES |SEE ALSO |AUTHOR |REPORTING BUGS |LICENSE |RESOURCES |COPYING |NOTES |COLOPHON | |
LIBTRACEFS(3) libtracefs ManualLIBTRACEFS(3)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
#include <tracefs.h> inttracefs_hist_add_sort_key(struct tracefs_hist *hist, const char *sort_key); inttracefs_hist_set_sort_key(struct tracefs_hist *hist, const char *sort_key,...); inttracefs_hist_sort_key_direction(struct tracefs_hist *hist, const char *sort_key, enum tracefs_hist_sort_directiondir); inttracefs_hist_add_name(struct tracefs_hist *hist, const char *name); inttracefs_hist_append_filter(struct tracefs_hist *hist, enum tracefs_filtertype, const char *field, enum tracefs_comparecompare, const char *val); inttracefs_hist_echo_cmd(struct trace_seq *s, struct tracefs_instance *instance, struct tracefs_hist *hist, enum tracefs_hist_commandcommand); inttracefs_hist_command(struct tracefs_instance *instance, struct tracefs_hist *hist, enum tracefs_hist_commandcommand); const char *tracefs_hist_get_name(struct tracefs_hist *hist); const char *tracefs_hist_get_event(struct tracefs_hist *hist); const char *tracefs_hist_get_system(struct tracefs_hist *hist);
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. Seehttps://www.kernel.org/doc/html/latest/trace/histogram.htmlfor more information.tracefs_hist_add_sort_key() will add a key to sort on. Thehist is the histogram descriptor to add the sort key to. Thesort_key is a string that must match either an already defined key of the histogram, or an already defined value. Ifhist already has sorting keys (previously added) the newsort_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. Thehist is the histogram descriptor to reset the sort key to. Thesort_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 oftracefs_hist_add_sort_key() must be NULL.tracefs_hist_sort_key_direction() allows to change the direction of an existing sort key ofhist. Thesort_key is the sort key to change, anddir 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). Thehist is the histogram to name, and thename is the name to give it.tracefs_hist_append_filter() creates a filter or appends to it for the histogram event. Depending ontype, it will build a string of tokens for parenthesis or logic statements, or it may add a comparison offield toval based oncompare. Iftype is:TRACEFS_FILTER_COMPARE- See belowTRACEFS_FILTER_AND - Append "&&" to the filterTRACEFS_FILTER_OR- Append "||" to the filterTRACEFS_FILTER_NOT- Append "!" to the filterTRACEFS_FILTER_OPEN_PAREN- Append "(" to the filterTRACEFS_FILTER_CLOSE_PAREN- Append ")" to the filterfield,compare, andval are ignored unlesstype is equal toTRACEFS_FILTER_COMPARE, thencompare will be used for the following:TRACEFS_COMPARE_EQ-field ==valTRACEFS_COMPARE_NE-field !=valTRACEFS_COMPARE_GT-field >valTRACEFS_COMPARE_GE-field >=valTRACEFS_COMPARE_LT-field <valTRACEFS_COMPARE_LE-field <=valTRACEFS_COMPARE_RE-field ~ "val" : wherefield is a string.TRACEFS_COMPARE_AND-field &val : wherefield is a flags field.trace_hist_echo_cmd() prints the commands needed to create the given histogram in the giveninstance, or NULL for the top level, into theseq. The command that is printed is described bycommand and shows the functionality that would be done bytracefs_hist_command(3).tracefs_hist_command() is called to process a command on the histogramhist for its event in the giveninstance, or NULL for the top level. Thecmd can be one of:TRACEFS_HIST_CMD_STARTor zero to start execution of the histogram.TRACEFS_HIST_CMD_PAUSEto pause the given histogram.TRACEFS_HIST_CMD_CONTto continue a paused histogram.TRACEFS_HIST_CMD_CLEARto reset the values of a histogram.TRACEFS_HIST_CMD_DESTROYto 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.tracefs_hist_alloc_nd() andtracefs_hist_add_key() both add a key and requires that key to have a type. The types may be:TRACEFS_HIST_KEY_NORMALor zero (0) which is to not modify the type.TRACEFS_HIST_KEY_HEXto display the key in hex.TRACEFS_HIST_KEY_SYMto 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_OFFSETsimilar toTRACEFS_HIST_KEY_SYMbut will also include the offset of the function to match the exact address.TRACEFS_HIST_KEY_SYSCALLIf 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_EXECNAMEIf "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_LOGwill display the key in a binary logarithmic scale.TRACEFS_HIST_KEY_USECSfor use with "common_timestamp" or TRACEFS_HIST_TIMESTAMP, in which case it will show the timestamp in microseconds instead of nanoseconds.
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 bytracefs_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 bytracefs_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 bytracefs_hist_free().tracefs_hist_alloc_nd() returns an allocated histogram descriptor which must be freed bytracefs_hist_free() or NULL on error.tracefs_hist_get_name(),tracefs_hist_get_event() andtracefs_hist_get_system() return strings owned by the histogram object. All the other functions return zero on success or -1 on error.
#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); }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 thelibtracefs (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 2025-08-11. (At that time, the date of the most recent commit that was found in the repository was 2025-06-02.) 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 isnot part of the original manual page), send a mail to man-pages@man7.orglibtracefs 1.7.0 12/22/2023LIBTRACEFS(3)Pages that refer to this page:tracefs_filter_pid_function(3), tracefs_filter_string_append(3), tracefs_hist_add_sort_key(3), tracefs_hist_start(3), tracefs_sql(3), tracefs_synth_alloc(3), tracefs_synth_create(3), tracefs_synth_echo_cmd(3)
HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH. | |