mirror of https://gitee.com/openkylin/linux.git
103 lines
2.7 KiB
Plaintext
103 lines
2.7 KiB
Plaintext
libtraceevent(3)
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================
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NAME
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----
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tep_get_header_page_size, tep_get_header_timestamp_size, tep_is_old_format -
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Get the data stored in the header page, in kernel context.
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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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int *tep_get_header_page_size*(struct tep_handle pass:[*]_tep_);
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int *tep_get_header_timestamp_size*(struct tep_handle pass:[*]_tep_);
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bool *tep_is_old_format*(struct tep_handle pass:[*]_tep_);
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--
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DESCRIPTION
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-----------
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These functions retrieve information from kernel context, stored in tracefs
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events/header_page. Old kernels do not have header page info, so default values
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from user space context are used.
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The _tep_get_header_page_size()_ function returns the size of a long integer,
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in kernel context. The _tep_ argument is trace event parser context.
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This information is retrieved from tracefs events/header_page, "commit" field.
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The _tep_get_header_timestamp_size()_ function returns the size of timestamps,
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in kernel context. The _tep_ argument is trace event parser context. This
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information is retrieved from tracefs events/header_page, "timestamp" field.
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The _tep_is_old_format()_ function returns true if the kernel predates
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the addition of events/header_page, otherwise it returns false.
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RETURN VALUE
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------------
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The _tep_get_header_page_size()_ function returns the size of a long integer,
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in bytes.
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The _tep_get_header_timestamp_size()_ function returns the size of timestamps,
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in bytes.
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The _tep_is_old_format()_ function returns true, if an old kernel is used to
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generate the tracing data, which has no event/header_page. If the kernel is new,
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or _tep_ is NULL, false is returned.
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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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...
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struct tep_handle *tep = tep_alloc();
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...
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int longsize;
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int timesize;
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bool old;
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longsize = tep_get_header_page_size(tep);
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timesize = tep_get_header_timestamp_size(tep);
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old = tep_is_old_format(tep);
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printf ("%s kernel is used to generate the tracing data.\n",
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old?"Old":"New");
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printf("The size of a long integer is %d bytes.\n", longsize);
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printf("The timestamps size is %d bytes.\n", timesize);
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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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*-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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