From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx> Add an API that allows modifying the buffer_percent of the tracing ring buffer. That is the amount that is written into the ring buffer before the trace is woken up. Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx> --- Documentation/libtracefs-instances-utils.txt | 28 +++++++++++++++++++- Documentation/libtracefs.txt | 2 ++ include/tracefs.h | 3 +++ src/tracefs-utils.c | 27 +++++++++++++++++++ 4 files changed, 59 insertions(+), 1 deletion(-) diff --git a/Documentation/libtracefs-instances-utils.txt b/Documentation/libtracefs-instances-utils.txt index bc8c9a7bf8e9..d2c4f163902d 100644 --- a/Documentation/libtracefs-instances-utils.txt +++ b/Documentation/libtracefs-instances-utils.txt @@ -4,7 +4,8 @@ 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. +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. SYNOPSIS -------- @@ -18,6 +19,8 @@ int *tracefs_instances_walk*(int (pass:[*]_callback_)(const char pass:[*], void 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_); +int *tracefs_instance_get_buffer_percent*(struct tracefs_instance pass:[*]_instance_); +int *tracefs_instance_set_buffer_percent*(struct tracefs_instance pass:[*]_instance_, int _val_); -- DESCRIPTION @@ -48,6 +51,29 @@ 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: + +[verse] +-- + 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. + RETURN VALUE ------------ The *tracefs_instance_get_name()* returns a string or NULL in case of the top diff --git a/Documentation/libtracefs.txt b/Documentation/libtracefs.txt index 8ca19a04fe77..529922580f8d 100644 --- a/Documentation/libtracefs.txt +++ b/Documentation/libtracefs.txt @@ -50,6 +50,8 @@ Trace instances: char pass:[*]*tracefs_instance_get_affinity_raw*(struct tracefs_instance pass:[*]_instance_); 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_); + int *tracefs_instance_get_buffer_percent*(struct tracefs_instance pass:[*]_instance_); + int *tracefs_instance_set_buffer_percent*(struct tracefs_instance pass:[*]_instance_, int _val_); Trace events: char pass:[*]pass:[*]*tracefs_event_systems*(const char pass:[*]_tracing_dir_); diff --git a/include/tracefs.h b/include/tracefs.h index 1722cbd60598..4be66b488536 100644 --- a/include/tracefs.h +++ b/include/tracefs.h @@ -64,6 +64,9 @@ ssize_t tracefs_instance_get_buffer_size(struct tracefs_instance *instance, int int tracefs_instance_set_buffer_size(struct tracefs_instance *instance, size_t size, int cpu); char **tracefs_instances(const char *regex); +int tracefs_instance_get_buffer_percent(struct tracefs_instance *instance); +int tracefs_instance_set_buffer_percent(struct tracefs_instance *instance, int val); + bool tracefs_instance_exists(const char *name); bool tracefs_file_exists(struct tracefs_instance *instance, const char *name); bool tracefs_dir_exists(struct tracefs_instance *instance, const char *name); diff --git a/src/tracefs-utils.c b/src/tracefs-utils.c index e67b698f5b99..50a7c7474145 100644 --- a/src/tracefs-utils.c +++ b/src/tracefs-utils.c @@ -643,3 +643,30 @@ bool tracefs_tracer_available(const char *tracing_dir, const char *tracer) tracefs_list_free(tracers); return ret; } + +/** + * tracefs_instance_get_buffer_percent - get the instance buffer percent + * @instance: The instance to get from (NULL for toplevel) + * + * Returns the buffer percent setting of the given instance. + * (-1 if not found). + */ +int tracefs_instance_get_buffer_percent(struct tracefs_instance *instance) +{ + long long val; + int ret; + + ret = tracefs_instance_file_read_number(instance, "buffer_percent", &val); + return !ret ? (int)val : ret; +} + +/** + * tracefs_instance_set_buffer_percent - set the instance buffer percent + * @instance: The instance to set (NULL for toplevel) + * + * Returns zero on success or -1 on error + */ +int tracefs_instance_set_buffer_percent(struct tracefs_instance *instance, int val) +{ + return tracefs_instance_file_write_number(instance, "buffer_percent", val); +} -- 2.42.0