From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx>
When the buffer_percent file was added to the kernel, the documentation
should have been updated to document what that file does.
Fixes: 03329f9939781 ("tracing: Add tracefs file buffer_percentage")
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
---
Documentation/trace/ftrace.rst | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst
index 933e7efb9f1b..16eabb00fa55 100644
--- a/Documentation/trace/ftrace.rst
+++ b/Documentation/trace/ftrace.rst
@@ -180,6 +180,21 @@ of ftrace. Here is a list of some of the key files:
Only active when the file contains a number greater than 0.
(in microseconds)
+ buffer_percent:
+
+ This is the water-mark for how much the ring buffer needs to be filled
+ before a waiter is woken up. That is, if an application call a
+ blocking read syscall on one of the per_cpu trace_pipe_raw files, it
+ will block until the given amount of data specified by buffer_percent
+ is in the ring buffer before it wakes the reader up. This also
+ controls how splice system calls are blocked on this file.
+
+ 0 - means to wake up as soon as there is any data in the ring buffer.
+ 50 - means to wake up when roughly half of the ring buffer sub-buffers
+ are full.
+ 100 - means to block until the ring buffer is totally full and is
+ about to start overwriting the older data.
+
buffer_size_kb:
This sets or displays the number of kilobytes each CPU
--
2.42.0
