139 lines
3.8 KiB
Plaintext
139 lines
3.8 KiB
Plaintext
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libtracecmd(3)
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=============
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NAME
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----
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tracecmd_read_cpu_first, tracecmd_read_data, tracecmd_read_at,
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tracecmd_free_record, tracecmd_get_tep - Read recorded events from a trace file.
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SYNOPSIS
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--------
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[verse]
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--
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*#include <trace-cmd.h>*
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struct tep_record pass:[*]*tracecmd_read_cpu_first*(struct tracecmd_input pass:[*]_handle_, int _cpu_);
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struct tep_record pass:[*]*tracecmd_read_data*(struct tracecmd_input pass:[*]_handle_, int _cpu_);
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struct tep_record pass:[*]*tracecmd_read_at*(struct tracecmd_input pass:[*]_handle_, unsigned long long _offset_, int pass:[*]_cpu_);
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void *tracecmd_free_record*(struct tep_record pass:[*]_record_);
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struct tep_handle pass:[*]*tracecmd_get_tep*(struct tracecmd_input pass:[*]_handle_);
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--
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DESCRIPTION
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-----------
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This set of APIs can be used to read tracing data from a trace file opened
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with _tracecmd_open()(3)_, _tracecmd_open_fd()(3)_ or _tracecmd_open_head()(3)_.
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The _tracecmd_read_cpu_first()_ function reads the first trace record
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for a given _cpu_ from a trace file associated with _handle_. The returned
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record must be freed with _tracecmd_free_record()_.
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The _tracecmd_read_data()_ function reads the next trace record for
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a given _cpu_ from a trace file associated with _handle_ and increments
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the read location pointer, so that the next call to _tracecmd_read_data()_
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will not read the same record again. The returned record must be freed
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with _tracecmd_free_record()_.
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The _tracecmd_read_at()_ function reads a trace record from a specific
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_offset_ within the file associated with _handle_. The CPU on which the
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recorded event occurred is stored in the _cpu_. The function does not
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change the current read location pointer. The returned record must be
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freed with _tracecmd_free_record()_.
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The _tracecmd_free_record()_ function frees a _record_ returned by any
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of the _tracecmd_read__ APIs.
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The _tracecmd_get_tep()_ function returns a tep context for a given
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_handle_.
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RETURN VALUE
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------------
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The _tracecmd_read_cpu_first()_, _tracecmd_read_data()_ and
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_tracecmd_read_at()_ functions return a pointer to struct tep_record or
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NULL in case of an error.The returned record must be freed with
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_tracecmd_free_record()_.
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The _tracecmd_get_tep()_ function returns a pointer to tep context or
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NULL if there is no tep context for the given _handle_. The returned
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tep pointer must *not* be freed.
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EXAMPLE
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-------
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[source,c]
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--
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#include <trace-cmd.h>
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...
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struct tracecmd_input *handle = tracecmd_open("trace.dat");
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if (!handle) {
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/* Failed to open trace.dat file */
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}
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...
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unsigned long long offset = 0;
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struct tep_record *rec;
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int cpu = 0;
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rec = tracecmd_read_cpu_first(handle, cpu);
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while (rec) {
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...
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if ( /* some interesting record noticed */) {
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/* store the offset of the interesting record */
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offset = rec->offset;
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}
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...
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tracecmd_free_record(rec);
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rec = tracecmd_read_data(handle, cpu);
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}
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...
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if (offset) {
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rec = tracecmd_read_at(handle, offset, &cpu);
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if (rec) {
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/* Got record at offset on cpu */
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...
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tracecmd_free_record(rec);
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}
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}
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...
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tracecmd_close(hadle);
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--
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FILES
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-----
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[verse]
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--
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*trace-cmd.h*
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Header file to include in order to have access to the library APIs.
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*-ltracecmd*
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Linker switch to add when building a program that uses the library.
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--
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SEE ALSO
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--------
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_libtracefs(3)_,
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_libtraceevent(3)_,
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_trace-cmd(1)_
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_trace-cmd.dat(5)_
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AUTHOR
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------
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[verse]
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--
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*Steven Rostedt* <rostedt@goodmis.org>
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*Tzvetomir Stoyanov* <tz.stoyanov@gmail.com>
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--
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REPORTING BUGS
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--------------
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Report bugs to <linux-trace-devel@vger.kernel.org>
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LICENSE
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-------
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libtracecmd is Free Software licensed under the GNU LGPL 2.1
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RESOURCES
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---------
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https://git.kernel.org/pub/scm/utils/trace-cmd/trace-cmd.git/
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COPYING
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-------
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Copyright \(C) 2020 VMware, Inc. Free use of this software is granted under
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the terms of the GNU Public License (GPL).
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