NAME¶

tep_get_header_page_size, tep_get_header_timestamp_size, tep_is_old_format - Get the data stored in the header page, in kernel context.

SYNOPSIS¶

#include <event-parse.h>
int tep_get_header_page_size(struct tep_handle *tep);
int tep_get_header_timestamp_size(struct tep_handle *tep);
bool tep_is_old_format(struct tep_handle *tep);

DESCRIPTION¶

These functions retrieve information from kernel context, stored in tracefs events/header_page. Old kernels do not have header page info, so default values from user space context are used.

The tep_get_header_page_size() function returns the size of a long integer, in kernel context. The tep argument is trace event parser context. This information is retrieved from tracefs events/header_page, "commit" field.

The tep_get_header_timestamp_size() function returns the size of timestamps, in kernel context. The tep argument is trace event parser context. This information is retrieved from tracefs events/header_page, "timestamp" field.

The tep_is_old_format() function returns true if the kernel predates the addition of events/header_page, otherwise it returns false.

RETURN VALUE¶

The tep_get_header_page_size() function returns the size of a long integer, in bytes.

The tep_get_header_timestamp_size() function returns the size of timestamps, in bytes.

The tep_is_old_format() function returns true, if an old kernel is used to generate the tracing data, which has no event/header_page. If the kernel is new, or tep is NULL, false is returned.

EXAMPLE¶

#include <event-parse.h>
...
struct tep_handle *tep = tep_alloc();
...


        int longsize;


        int timesize;


        bool old;


        longsize = tep_get_header_page_size(tep);


        timesize = tep_get_header_timestamp_size(tep);


        old = tep_is_old_format(tep);


        printf ("%s kernel is used to generate the tracing data.\n",


                old?"Old":"New");


        printf("The size of a long integer is %d bytes.\n", longsize);


        printf("The timestamps size is %d bytes.\n", timesize);
...

FILES¶

event-parse.h


        Header file to include in order to have access to the library APIs.
-ltraceevent


        Linker switch to add when building a program that uses the library.

SEE ALSO¶

libtraceevent(3), trace-cmd(1)

AUTHOR¶

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

REPORTING BUGS¶

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

LICENSE¶

libtraceevent is Free Software licensed under the GNU LGPL 2.1

RESOURCES¶

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

NOTES¶

1.

rostedt@goodmis.org

2.

tz.stoyanov@gmail.com

3.

linux-trace-devel@vger.kernel.org