LIBTRACECMD(3) libtracefs Manual LIBTRACECMD(3)
NAME
tracecmd_get_first_ts, tracecmd_add_ts_offset, tracecmd_get_tsc2nsec -
Handle time stamps from a trace file.
SYNOPSIS
#include <trace-cmd.h>
unsigned long long tracecmd_get_first_ts(struct tracecmd_input *handle);
void tracecmd_add_ts_offset(struct tracecmd_input *handle, long long offset);
int tracecmd_get_tsc2nsec(struct tracecmd_input *handle, int *mult, int pass[*]shift, unsigned long long *offset);
DESCRIPTION
This set of APIs can be used to read tracing data from a trace file
opened with tracecmd_open()(3), tracecmd_open_fd()(3) or
tracecmd_open_head()(3).
The tracecmd_get_first_ts() function returns the time stamp of the
first record in the handle.
The tracecmd_add_ts_offset() function adds an offset to each of the
records in the handle that represents a trace file. This is useful for
associating two different tracing files by their offset (for example a
trace file from a host and a trace file from a guest that were not
synchronized when created).
The tracecmd_get_tsc2nsec returns the calculation values that convert
the raw timestamp into nanoseconds. The parameters are pointers to the
storage to save the values, or NULL to ignore them. The multiplier will
be saved in mult, the shift value will be saved in shift, and the
offset value will be saved in offset, if the corresponding parameters
are not NULL.
RETURN VALUE
The tracecmd_get_first_ts() function returns the timestamp of the first
record in a trace file for the given handle.
The tracecmd_get_tsc2nsec() returns 0 if the tracing clock supports the
shift values and -1 otherwise. Note, that if the trace file has the
TSC2NSEC option, the values returned in the parameters may still be
valid even if the function itself returns -1. The return value only
notes if the values will be used in the calculations of the given
clock.
EXAMPLE
#include <stdlib.h>
#include <trace-cmd.h>
static int print_events(struct tracecmd_input *handle, struct tep_record *record, int cpu, void *data)
{
static struct trace_seq seq;
struct tep_handle *tep = tracecmd_get_tep(handle);
const char *file = tracecmd_get_private(handle);
if (!seq.buffer)
trace_seq_init(&seq);
trace_seq_reset(&seq);
trace_seq_printf(&seq, "%s: ", file);
tep_print_event(tep, &seq, record, "%6.1000d [%03d] %s-%d %s: %s\n",
TEP_PRINT_TIME, TEP_PRINT_CPU, TEP_PRINT_COMM, TEP_PRINT_PID,
TEP_PRINT_NAME, TEP_PRINT_INFO);
trace_seq_terminate(&seq);
trace_seq_do_printf(&seq);
return 0;
}
int main(int argc, char **argv)
{
struct tracecmd_input **handles = NULL;
unsigned long long ts, first_ts = 0;
unsigned long long offset;
int multi;
int shift;
int nr_handles = 0;
int ret;
int i;
if (argc < 2) {
printf("usage: %s trace.dat [trace.dat ...]\n", argv[0]);
exit(-1);
}
for (i = 1; i < argc; i++) {
handles = realloc(handles, sizeof(*handles) * (nr_handles + 1));
if (!handles)
exit(-1);
handles[nr_handles] = tracecmd_open(argv[i], 0);
if (!handles[nr_handles])
exit(-1);
ret = tracecmd_get_tsc2nsec(handles[nr_handles], &multi, &shift, &offset);
if (!ret)
printf(" %s has tsc2nsec calculations of mult:%d shift:%d offset:%lld\n",
argv[i], multi, shift, offset);
tracecmd_set_private(handles[nr_handles], argv[i]);
ts = tracecmd_get_first_ts(handles[nr_handles]);
if (!first_ts || ts < first_ts)
first_ts = ts;
nr_handles++;
}
/* Set the time stamp to start at the first record found */
for (i = 0; i < nr_handles; i++)
tracecmd_add_ts_offset(handles[i], -first_ts);
tracecmd_iterate_events_multi(handles, nr_handles, print_events, NULL);
for (i = 0; i < nr_handles; i++)
tracecmd_close(handles[i]);
free(handles);
}
FILES
trace-cmd.h
Header file to include in order to have access to the library APIs.
-ltracecmd
Linker switch to add when building a program that uses the library.
SEE ALSO
libtracefs(3), libtraceevent(3), trace-cmd(1) trace-cmd.dat(5)
AUTHOR
Steven Rostedt <rostedt@goodmis.org[1]>
Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>
REPORTING BUGS
Report bugs to <linux-trace-devel@vger.kernel.org[3]>
LICENSE
libtracecmd is Free Software licensed under the GNU LGPL 2.1
RESOURCES
https://git.kernel.org/pub/scm/utils/trace-cmd/trace-cmd.git/
COPYING
Copyright (C) 2020 VMware, Inc. Free use of this software is granted
under the terms of the GNU Public License (GPL).
NOTES
1. rostedt@goodmis.org
mailto:rostedt@goodmis.org
2. tz.stoyanov@gmail.com
mailto:tz.stoyanov@gmail.com
3. linux-trace-devel@vger.kernel.org
mailto:linux-trace-devel@vger.kernel.org
libtracefs 04/08/2024 LIBTRACECMD(3)
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