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
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