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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | EXAMPLE | FILES | SEE ALSO | AUTHOR | REPORTING BUGS | LICENSE | RESOURCES | COPYING | NOTES | COLOPHON |
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LIBTRACEFS(3) libtracefs Manual LIBTRACEFS(3)
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,
tracefs_instance_get_buffer_percent,
tracefs_instance_set_buffer_percent - Helper functions for working
with tracing instances.
#include <tracefs.h>
const char *tracefs_instance_get_name(struct tracefs_instance *instance);
const char *tracefs_instance_get_trace_dir(struct tracefs_instance *instance);
int tracefs_instances_walk(int (*callback)(const char *, void *), void *context);
bool tracefs_instance_exists(const char *name);
size_t tracefs_instance_get_buffer_size(struct tracefs_instance *instance, int cpu);
int tracefs_instance_set_buffer_size(struct tracefs_instance *instance, size_t size, int cpu);
int tracefs_instance_get_buffer_percent(struct tracefs_instance *instance);
int tracefs_instance_set_buffer_percent(struct tracefs_instance *instance, int val);
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.
The tracefs_instance_set_buffer_percent() sets the buffer percent
value of the tracing ring buffer for instance or the top level
buffer if instance is NULL. The buffer percent decides when
readers on tracefs_cpu_read(3), tracefs_cpu_buffered_read(3),
tracefs_cpu_write(3) and tracefs_cpu_pipe(3) will block when
O_NONBLOCK is not set. The value of val must be between 0 and 100,
where:
0 - block until there’s any data in the ring buffer
1 - block until 1% of the ring buffer sub-buffers are filled
50 - block until 50% of the ring buffer sub-buffers are filled
100 - block until the entire ring buffer is filled
Note, any number from 0 to 100 can be used where it is the
percentage of the ring buffer that must be filled before a blocked
reader will be notified that there’s data to be retrieved.
The tracefs_instance_get_buffer_percent() retrieves the current
buffer percent setting of the tracing ring buffer for instance or
the top level buffer if instance is NULL.
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.
#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 */
}
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.
libtracefs(3), libtraceevent(3), trace-cmd(1)
Steven Rostedt <rostedt@goodmis.org[1]>
Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>
Report bugs to <linux-trace-devel@vger.kernel.org[3]>
libtracefs is Free Software licensed under the GNU LGPL 2.1
https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/
Copyright (C) 2020 VMware, Inc. Free use of this software is
granted under the terms of the GNU Public License (GPL).
1. rostedt@goodmis.org
mailto:rostedt@goodmis.org
2. tz.stoyanov@gmail.com
mailto:tz.stoyanov@gmail.com
3. linux-trace-devel@vger.kernel.org
mailto:linux-trace-devel@vger.kernel.org
This page is part of the libtracefs (Linux kernel trace file
system library) project. Information about the project can be
found at ⟨https://www.trace-cmd.org/⟩. If you have a bug report
for this manual page, see ⟨https://www.trace-cmd.org/⟩. This page
was obtained from the project's upstream Git repository
⟨https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git⟩ on
2025-02-02. (At that time, the date of the most recent commit
that was found in the repository was 2024-11-22.) If you discover
any rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page,
or you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a
mail to man-pages@man7.org
libtracefs 1.8.1 01/02/2025 LIBTRACEFS(3)
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HTML rendering created 2025-02-02 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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