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. Acked-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx> Fixes: 03329f9939781 ("tracing: Add tracefs file buffer_percentage") Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx> --- Changes since v2: https://lore.kernel.org/linux-trace-kernel/20231226130149.4685c838@xxxxxxxxxxxxxxxxxx - s/watermark/water-mark/ (Randy Dunlap) - Added '::' and indented the number list so that it has better formatting (kernel test robot) Documentation/trace/ftrace.rst | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst index 933e7efb9f1b..917501a2f348 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 watermark for how much the ring buffer needs to be filled + before a waiter is woken up. That is, if an application calls 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 the 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