tep_get_header_page_size(3)

1LIBTRACEEVENT(3)             libtraceevent Manual             LIBTRACEEVENT(3)
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NAME

6       tep_get_header_page_size, tep_get_header_timestamp_size,
7       tep_is_old_format - Get the data stored in the header page, in kernel
8       context.
9

SYNOPSIS

11       #include <event-parse.h>
12
13       int tep_get_header_page_size(struct tep_handle *tep);
14       int tep_get_header_timestamp_size(struct tep_handle *tep);
15       bool tep_is_old_format(struct tep_handle *tep);
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DESCRIPTION

18       These functions retrieve information from kernel context, stored in
19       tracefs events/header_page. Old kernels do not have header page info,
20       so default values from user space context are used.
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22       The tep_get_header_page_size() function returns the size of a long
23       integer, in kernel context. The tep argument is trace event parser
24       context. This information is retrieved from tracefs events/header_page,
25       "commit" field.
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27       The tep_get_header_timestamp_size() function returns the size of
28       timestamps, in kernel context. The tep argument is trace event parser
29       context. This information is retrieved from tracefs events/header_page,
30       "timestamp" field.
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32       The tep_is_old_format() function returns true if the kernel predates
33       the addition of events/header_page, otherwise it returns false.
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RETURN VALUE

36       The tep_get_header_page_size() function returns the size of a long
37       integer, in bytes.
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39       The tep_get_header_timestamp_size() function returns the size of
40       timestamps, in bytes.
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42       The tep_is_old_format() function returns true, if an old kernel is used
43       to generate the tracing data, which has no event/header_page. If the
44       kernel is new, or tep is NULL, false is returned.
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EXAMPLE

47           #include <event-parse.h>
48           ...
49           struct tep_handle *tep = tep_alloc();
50           ...
51                   int longsize;
52                   int timesize;
53                   bool old;
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55                   longsize = tep_get_header_page_size(tep);
56                   timesize = tep_get_header_timestamp_size(tep);
57                   old = tep_is_old_format(tep);
58
59                   printf ("%s kernel is used to generate the tracing data.\n",
60                           old?"Old":"New");
61                   printf("The size of a long integer is %d bytes.\n", longsize);
62                   printf("The timestamps size is %d bytes.\n", timesize);
63           ...
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FILES

66           event-parse.h
67                   Header file to include in order to have access to the library APIs.
68           -ltraceevent
69                   Linker switch to add when building a program that uses the library.
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AUTHOR

75           Steven Rostedt <rostedt@goodmis.org[1]>, author of libtraceevent.
76           Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>, author of this man page.
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REPORTING BUGS

79       Report bugs to <linux-trace-devel@vger.kernel.org[3]>
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LICENSE

82       libtraceevent is Free Software licensed under the GNU LGPL 2.1
83

RESOURCES

85       https://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git/
86

NOTES

88        1. rostedt@goodmis.org
89           mailto:rostedt@goodmis.org
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91        2. tz.stoyanov@gmail.com
92           mailto:tz.stoyanov@gmail.com
93
94        3. linux-trace-devel@vger.kernel.org
95           mailto:linux-trace-devel@vger.kernel.org
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99libtraceevent 1.5.3               04/15/2022                  LIBTRACEEVENT(3)