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libtraceevent: Man pages for libtraceevent event print related API
Added new man page, describing tep_print_event() libtraceevent API. Signed-off-by: Tzvetomir Stoyanov <tstoyanov@vmware.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: linux-trace-devel@vger.kernel.org Link: http://lore.kernel.org/linux-trace-devel/20190801075012.22098-1-tz.stoyanov@gmail.com Link: http://lore.kernel.org/lkml/20190919212541.553160178@goodmis.org Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Tzvetomir Stoyanov
Arnaldo Carvalho de Melo
parent
5c8da72dc2
commit
4ab91deacc
130
tools/lib/traceevent/Documentation/libtraceevent-event_print.txt
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130
tools/lib/traceevent/Documentation/libtraceevent-event_print.txt
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libtraceevent(3)
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================
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NAME
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----
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tep_print_event - Writes event information into a trace sequence.
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SYNOPSIS
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--------
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[verse]
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--
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*#include <event-parse.h>*
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*#include <trace-seq.h>*
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void *tep_print_event*(struct tep_handle pass:[*]_tep_, struct trace_seqpass:[*]_s_, struct tep_record pass:[*]_record_, const char pass:[*]_fmt_, _..._)
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--
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DESCRIPTION
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-----------
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The _tep_print_event()_ function parses the event information of the given
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_record_ and writes it into the trace sequence _s_, according to the format
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string _fmt_. The desired information is specified after the format string.
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The _fmt_ is printf-like format string, following arguments are supported:
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[verse]
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--
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TEP_PRINT_PID, "%d" - PID of the event.
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TEP_PRINT_CPU, "%d" - Event CPU.
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TEP_PRINT_COMM, "%s" - Event command string.
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TEP_PRINT_NAME, "%s" - Event name.
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TEP_PRINT_LATENCY, "%s" - Latency of the event. It prints 4 or more
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fields - interrupt state, scheduling state,
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current context, and preemption count.
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Field 1 is the interrupt enabled state:
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d : Interrupts are disabled
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. : Interrupts are enabled
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X : The architecture does not support this
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information
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Field 2 is the "need resched" state.
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N : The task is set to call the scheduler when
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possible, as another higher priority task
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may need to be scheduled in.
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. : The task is not set to call the scheduler.
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Field 3 is the context state.
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. : Normal context
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s : Soft interrupt context
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h : Hard interrupt context
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H : Hard interrupt context which triggered
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during soft interrupt context.
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z : NMI context
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Z : NMI context which triggered during hard
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interrupt context
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Field 4 is the preemption count.
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. : The preempt count is zero.
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On preemptible kernels (where the task can be scheduled
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out in arbitrary locations while in kernel context), the
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preempt count, when non zero, will prevent the kernel
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from scheduling out the current task. The preempt count
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number is displayed when it is not zero.
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Depending on the kernel, it may show other fields
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(lock depth, or migration disabled, which are unique to
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specialized kernels).
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TEP_PRINT_TIME, %d - event time stamp. A divisor and precision can be
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specified as part of this format string:
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"%precision.divisord". Example:
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"%3.1000d" - divide the time by 1000 and print the first
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3 digits before the dot. Thus, the time stamp
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"123456000" will be printed as "123.456"
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TEP_PRINT_INFO, "%s" - event information.
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TEP_PRINT_INFO_RAW, "%s" - event information, in raw format.
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--
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EXAMPLE
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-------
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[source,c]
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--
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#include <event-parse.h>
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#include <trace-seq.h>
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...
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struct trace_seq seq;
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trace_seq_init(&seq);
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struct tep_handle *tep = tep_alloc();
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...
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void print_my_event(struct tep_record *record)
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{
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trace_seq_reset(&seq);
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tep_print_event(tep, s, record, "%16s-%-5d [%03d] %s %6.1000d %s %s",
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TEP_PRINT_COMM, TEP_PRINT_PID, TEP_PRINT_CPU,
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TEP_PRINT_LATENCY, TEP_PRINT_TIME, TEP_PRINT_NAME,
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TEP_PRINT_INFO);
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}
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...
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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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*event-parse.h*
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Header file to include in order to have access to the library APIs.
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*trace-seq.h*
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Header file to include in order to have access to trace sequences related APIs.
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Trace sequences are used to allow a function to call several other functions
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to create a string of data to use.
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*-ltraceevent*
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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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_libtraceevent(3)_, _trace-cmd(1)_
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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>, author of *libtraceevent*.
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*Tzvetomir Stoyanov* <tz.stoyanov@gmail.com>, author of this man page.
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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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libtraceevent 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/linux/kernel/git/torvalds/linux.git
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