diff options
| author | Steven Rostedt (Google) <rostedt@goodmis.org> | 2023-12-29 12:24:02 -0500 |
|---|---|---|
| committer | Jonathan Corbet <corbet@lwn.net> | 2024-01-03 14:41:52 -0700 |
| commit | 4b2df884b8971f0f18e0c5d7ef9e5b9cb740cc9a (patch) | |
| tree | 267ddab59396311ea7a4e40c2e83b23ce9d3d6fc /Documentation/trace | |
| parent | d78bcf646cf52097d3a36330404291cf84aabf85 (diff) | |
ring-buffer/Documentation: Add documentation on buffer_percent file
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@kernel.org>
Fixes: 03329f9939781 ("tracing: Add tracefs file buffer_percentage")
Signed-off-by: "Steven Rostedt (Google)" <rostedt@goodmis.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20231229122402.537eb252@gandalf.local.home
Diffstat (limited to 'Documentation/trace')
| -rw-r--r-- | Documentation/trace/ftrace.rst | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst index 9ef362dae9df..16122a8895ba 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 |