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| -rw-r--r-- | Documentation/libtraceevent-header_page.txt | 102 |
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diff --git a/Documentation/libtraceevent-header_page.txt b/Documentation/libtraceevent-header_page.txt new file mode 100644 index 0000000..31b66e0 --- /dev/null +++ b/Documentation/libtraceevent-header_page.txt @@ -0,0 +1,102 @@ +libtraceevent(3) +================ + +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 +-------- +[verse] +-- +*#include <event-parse.h>* + +int *tep_get_header_page_size*(struct tep_handle pass:[*]_tep_); +int *tep_get_header_timestamp_size*(struct tep_handle pass:[*]_tep_); +bool *tep_is_old_format*(struct tep_handle pass:[*]_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 +------- +[source,c] +-- +#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 +----- +[verse] +-- +*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 +------ +[verse] +-- +*Steven Rostedt* <rostedt@goodmis.org>, author of *libtraceevent*. +*Tzvetomir Stoyanov* <tz.stoyanov@gmail.com>, author of this man page. +-- +REPORTING BUGS +-------------- +Report bugs to <linux-trace-devel@vger.kernel.org> + +LICENSE +------- +libtraceevent is Free Software licensed under the GNU LGPL 2.1 + +RESOURCES +--------- +https://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git/ |