| Message ID | 20231229122402.537eb252@gandalf.local.home (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | [v3] ring-buffer/Documentation: Add documentation on buffer_percent file | expand |
On 12/29/23 09:24, Steven Rostedt wrote: > From: "Steven Rostedt (Google)" <rostedt@goodmis.org> > > 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> LGTM. Thanks. Acked-by: Randy Dunlap <rdunlap@infradead.org> > --- > Changes since v2: https://lore.kernel.org/linux-trace-kernel/20231226130149.4685c838@gandalf.local.home > > - s/watermark/water-mark/ (Randy Dunlap) That comment is backwards. :) No new patch needed IMO. > > - 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
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