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Diffstat (limited to 'Documentation/libtracefs-instances-utils.txt')
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diff --git a/Documentation/libtracefs-instances-utils.txt b/Documentation/libtracefs-instances-utils.txt new file mode 100644 index 0000000..bc8c9a7 --- /dev/null +++ b/Documentation/libtracefs-instances-utils.txt @@ -0,0 +1,141 @@ +libtracefs(3) +============= + +NAME +---- +tracefs_instance_get_name, tracefs_instance_get_trace_dir, tracefs_instances_walk, tracefs_instance_exists, +tracefs_instance_get_buffer_size, tracefs_instance_set_buffer_size - Helper functions for working with tracing instances. + +SYNOPSIS +-------- +[verse] +-- +*#include <tracefs.h>* + +const char pass:[*]*tracefs_instance_get_name*(struct tracefs_instance pass:[*]_instance_); +const char pass:[*]*tracefs_instance_get_trace_dir*(struct tracefs_instance pass:[*]_instance_); +int *tracefs_instances_walk*(int (pass:[*]_callback_)(const char pass:[*], void pass:[*]), void pass:[*]_context)_; +bool *tracefs_instance_exists*(const char pass:[*]_name_); +size_t *tracefs_instance_get_buffer_size*(struct tracefs_instance pass:[*]_instance_, int _cpu_); +int *tracefs_instance_set_buffer_size*(struct tracefs_instance pass:[*]_instance_, size_t _size_, int _cpu_); +-- + +DESCRIPTION +----------- +Helper functions for working with trace instances. + +The *tracefs_instance_get_name()* function returns the name of the given _instance_. +Note that the top instance has no name, the function returns NULL for it. + +The *tracefs_instance_get_trace_dir()* function returns the tracing directory, where +the given _instance_ is configured. + +The *tracefs_instances_walk()* function walks through all configured tracing +instances in the system and calls _callback_ for each one of them. The _context_ +argument is passed to the _callback_, together with the instance name. If the +_callback_ returns non-zero, the iteration stops. Note, the _callback_ is not +called for the top top instance. + +The *tracefs_instance_exists()* function checks if an instance with the given +_name_ exists in the system. + +The *tracefs_instace_get_buffer_size()* returns the size of the ring buffer. If _cpu_ +is negative, it returns the total size of all the per CPU ring buffers, otherwise +it returns the size of the per CPU ring buffer for _cpu_. + +The *tracefs_instance_set_buffer_size()* function sets the size of the ring buffer. +If _cpu_ is negative, then it sets all the per CPU ring buffers to _size_ (note +the total size is the number of CPUs * _size_). If _cpu_ is specified, then it only +sets the size of the per CPU ring buffer. + +RETURN VALUE +------------ +The *tracefs_instance_get_name()* returns a string or NULL in case of the top +instance. The returned string must _not_ be freed. + +The *tracefs_instance_get_trace_dir()* returns a string or NULL in case of an error. +The returned string must _not_ be freed. + +The *tracefs_instances_walk()* function returns 0, if all instances were iterated, 1 +if the iteration was stopped by the _callback_, or -1 in case of an error. + +The *tracefs_instance_exists()* returns true if an instance with the given _name_ +exists in the system or false otherwise. + +The *tracefs_instance_get_buffer_size()* returns the size of the ring buffer depending on +the _cpu_ value passed in, or -1 on error. + +The *tracefs_instance_set_buffer_size()* returns zero on success and -1 on error. + +EXAMPLE +------- +[source,c] +-- +#include <tracefs.h> + +struct tracefs_instance *inst; +.... +char *name = tracefs_instance_get_name(inst); + if(name) { + /* Got name of the instance */ + } +char *dir = tracefs_instance_get_trace_dir(inst); + if(dir) { + /* Got tracing directory of the instance */ + } +... +static int instance_walk(char *name, void *context) +{ + /* Got instance with name */ + return 0; +} +... + if (tracefs_instances_walk(instance_walk, NULL) < 0) { + /* Error walking through the instances */ + } +... + if (tracefs_instance_exists("foo")) { + /* There is instance with name foo in the system */ + } else { + /* There is no instance with name foo in the system */ + } +-- +FILES +----- +[verse] +-- +*tracefs.h* + Header file to include in order to have access to the library APIs. +*-ltracefs* + Linker switch to add when building a program that uses the library. +-- + +SEE ALSO +-------- +*libtracefs*(3), +*libtraceevent*(3), +*trace-cmd*(1) + +AUTHOR +------ +[verse] +-- +*Steven Rostedt* <rostedt@goodmis.org> +*Tzvetomir Stoyanov* <tz.stoyanov@gmail.com> +-- +REPORTING BUGS +-------------- +Report bugs to <linux-trace-devel@vger.kernel.org> + +LICENSE +------- +libtracefs is Free Software licensed under the GNU LGPL 2.1 + +RESOURCES +--------- +https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/ + +COPYING +------- +Copyright \(C) 2020 VMware, Inc. Free use of this software is granted under +the terms of the GNU Public License (GPL). |